- Email: [email protected]
A comparative study of embryonic development of some bird species with different patterns of postnatal growth
ARTICLE IN PRESS
ZOOLOGY Zoology 108 (2005) 81–95 www.elsevier.de/zool
A comparative study of embryonic development of some bird species with different patterns of postnatal growth Jonas Blom, Clas Lilja Department of Biology and Environmental Science, Kalmar University, Kalmar SE-391 82, Sweden Received 14 January 2005; accepted 23 February 2005
Abstract Some studies show that birds with high postnatal growth rates (e.g. altricial species) are characterized by a rapid early development of ‘‘supply’’ organs, such as digestive organs. Birds with low postnatal growth rates (e.g. precocial species) exhibit a slower early development of these organs and a more rapid early development of other ‘‘demand’’ organs, such as brain, muscles, skeleton and feathers. To test whether these differences can be traced back to early embryonic development and whether they can be associated with changes in developmental timing, i.e. heterochrony, we compared embryos of the precocial quail and the altricial fieldfare, two bird species with low and high postnatal growth rates, respectively. We used classical staging techniques that use developmental landmarks to categorize embryonic maturity as well as morphological measurements. These techniques were combined with immune detection of muscle specific proteins in the somites. Our data showed that the anlagen of the head, brain and eyes develop earlier in the quail than in the fieldfare in contrast to the gut which develops earlier in the fieldfare than in the quail. Our data also showed that the quail and the fieldfare displayed different rates of myotome formation in the somites which contribute to muscle formation in the limbs and thorax. We believe these observations are connected with important differences in neonatal characteristics, such as the size of the brain, eyes, organs for locomotion and digestion. This leads us to the conclusion that selection for late ontogenetic characteristics can alter early embryonic development and that growth rate is of fundamental importance for the patterning of avian embryonic development. It also appears that this comparative system offers excellent opportunities to test hypotheses about heterochrony. r 2005 Elsevier GmbH. All rights reserved. Keywords: Altricial species; Precocial species; Embryonic development; Myotome formation; Heterochrony; PAX-7
Introduction Early embryonic development has traditionally been viewed as invariant within vertebrate taxa (Von Baer, 1828; Darwin, 1859; Haeckel, 1891, reviewed in Gould, 1977; Wallace, 1997). It has been suggested that most or all vertebrate embryos pass through a virtually identical Corresponding author. Tel.: +46 480 446170; fax: +46 480 447305.
E-mail address: [email protected] (C. Lilja). 0944-2006/$ - see front matter r 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.zool.2005.02.001
conserved stage, the phylotypic stage (reviewed by Raff, 1994, 1996; Richardson et al., 1997). This view has been the common consensus in textbooks over the last century (Alberts et al., 1994). Embryonic resemblance at the tail bud stage has been linked with a conserved pattern of developmental gene expression, i.e. the zootype (Slack et al., 1993; Slack and Ruvkun, 1997). It has been argued that specific differences between vertebrate embryos arise largely through modifications at later stages of development (Wolpert, 1991; Slack et al., 1993;
ARTICLE IN PRESS 82
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Alberts et al., 1994; Duboule, 1994; Ricklefs and Starck, 1998; reviewed in Richardson et al., 1997). Such modifications may be a result of allometric growth and/or heterochrony, changes in developmental timing (de Beer, 1951; Gould, 1977; Raff and Wray, 1989; McKinney and McNamara, 1991; Gould, 1992; Duboule, 1994; Richardson, 1995; Klingenberg, 1998; Smith, 2001). While there is a large body of data dealing with heterochrony at later stages of development, actual data about developmental timing during early to midembryonic stages are scarce. A few studies, however, have presented evidence on significant variation between early vertebrate embryos (e.g. Richardson, 1995; Richardson et al., 1997; Smith, 1997; Lilja and Blom, 1999; Richardson, 1999; Lilja et al., 2001; Smith, 2001, 2002; Schmidt and Starck, 2004). These studies show that adult variation can be generated at a variety of embryonic stages. It has long been recognized that growth rate and size are significantly correlated in birds (Ricklefs, 1968, 1973, 1979b; Bjo¨rnhag, 1979; Starck, 1993; Ricklefs et al., 1998). Among birds of similar size, however, species deviations from this relationship can sometimes be significant. Much of this deviation is related to the degree of precocity of the chick. At the one extreme are precocial species (Nice, 1962) whose young hatch covered with down, eyes open, organs of locomotion fairly well developed, and able to feed on their own. At the other extreme are altricial species (Nice, 1962) whose young hatch blind, naked and with less well-developed organs of locomotion, but with highly developed organs of digestion and a dependence on parental care (Portmann, 1955; Neff, 1972; Lilja, 1983; Starck and Ricklefs, 1998a; Fig. 1). On average altricial bird species grow three to four times more rapidly than precocial species (Ricklefs, 1968, 1973, 1979a, b; Bjo¨rnhag, 1979; Starck, 1993; Ricklefs et al., 1998). Despite extensive work on avian growth and development, less attention has been paid to developmental differences which characterize different bird taxa. It has
Fig. 1. The precocial quail (left) and the altricial fieldfare (right) at the time of hatching.
been suggested, however, that growth rate may be of fundamental importance for generating changes in the pattern of organ development (Lilja et al., 1985; Katanbaf et al., 1988; Lilja and Marks, 1991; Clum et al., 1995; Lilja et al., 2001; Blom and Lilja, 2004a, b). It appears that individuals and species with higher than average postnatal growth rates are those that allocate a large share of the early growth to rapid development of ‘‘supply’’ organs, such as the digestive organs. Such a large early investment in these organs may have been at the expense of growth directed to ‘‘demand’’ organs, such as brain, muscles, skeleton and feathers. From these and other studies (Lilja, 1983; Konarzewski et al., 1989; Jackson and Diamond, 1995; Konarzewski et al., 1996; Lilja, 1997; Ricklefs et al., 1998; Konarzewski and Starck, 2000) it can be inferred that the ‘‘supply’’ organs usually function close to their maximum rate and that any increase in assimilation can only be accomplished by a change in the organ growth pattern. Hence, it follows that this restriction may limit the range of morphological variation that can be produced to the patterns permitted by ‘‘supply’’ and ‘‘demand’’ organ relationships. In view of these considerations, we assumed that different patterns of postnatal growth are established during embryonic stages, so that embryonic development forms part of a wider complex of ‘‘supply’’ and ‘‘demand’’ organ relationships. We tested this prediction by comparing embryonic development in birds with very different postnatal growth patterns. We used embryos of the precocial quail (Coturnix japonica) and the altricial fieldfare (Turdus pilaris), two species with low and high growth rates, respectively. In particular, we tested whether late ontogenetic neonatal characteristics, such as large and small brains, eyes, and organs of locomotion and digestion may be established at early embryonic stages, i.e. during the phylotypic period, even though these stages are usually considered to be highly conserved. We used classical staging techniques that use developmental landmarks to categorize embryonic maturity as well as morphological measurements of those ‘‘supply’’ and ‘‘demand’’ organs in development. These techniques were combined with immune detection of PAX-7 (paired box homeotic gene) and myosin heavy chain (MyHC), two proteins essential for the patterning of muscle cell formation. PAX-7 is expressed in the segmental plate and the dermamyotome prior to myotome formation (Jostes et al., 1990; Bober et al., 1994; Goulding et al., 1994; Kawakami et al., 1997; Lilja et al., 2001). In slightly older embryos, PAX-7 is also expressed in myotomes and myoblast cells migrating and forming limb and trunk muscle precursors (Kawakami et al., 1997; Lilja et al., 2001). As soon as the myoblast cells from the myotome begin to fuse they are post-mitotic, terminally differentiated muscle cells characterized by expressing muscle specific proteins, such as
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
83
developmental timing should be associated with either an earlier or later occurrence of this marker of late muscle cell differentiation, provided the initial somite number was identical.
Material and methods Embryos Fig. 2. Schematic figure showing how the morphological measurements were made. (Left) (a) Head length (distance from isthmus to anterior-most part of telencephalon); (b) midbrain length (distance from isthmus to mesencephalon/ diencephalon junction); (c) midbrain height (distance from the dorsal-most to ventral-most part of mesencephalon); (d) Optic cup (diameter); (e) bud (wing and leg) length (distance from the midline at the basal bud border to apex of bud curve, distal-most part). (Upper right) (f) Embryo length (distance from the anterior-most part of the embryo proper to the posterior part of hensens node); (g) forebrain (width); (h) anterior part (distance from the anterior-most part of the embryo proper to 1st somite); posterior part (length of the embryo less the length of the anterior part). (Lower right) Gut tube, development of lateral folds: (i) distance between lateral folds; (j) gut closure (distance of gut closure progression, anteriorly to posteriorly).
MyHC. Hence, we used MyHC as a late marker of muscle cell differentiation (Christ et al., 1978; Ordahl and LeDouarin, 1992; Coutinho et al., 1993; Lilja et al., 2001). We predicted, therefore, that differences in Table 1.
Quail eggs were obtained from the Southern Regional Poultry Genetics Laboratory at the University of Georgia and stored at 7–10 1C for less than a week. Incubation was conducted at 37 1C in a humidified chamber, embryos collected, fixed in 4% paraformaldehyde, dehydrated in alcohol and then staged according to Hamburger and Hamilton (1951). Eggs of the fieldfare were incubated in the nests by the parent birds. Embryos were then collected, fixed, dehydrated and staged as above. A few embryos of some other precocial species (ostrich Struthio camelus, red jungle fowl Gallus gallus, pheasant Phasianus colchicus) and altricial species (starling Sturnus vulgaris, pied wagtail Motacilla alba, great tit Parus major, blue tit Parus carruleus, house sparrow Passer domesticus) were presented for comparative purposes. They were obtained from various sources: The Swedish University of Agricultural Sciences, The Hubrecht collection at the Netherlands Institute of Developmental Embryology, commercial breeders, and in the field. The quail and the fieldfare (Fig. 1) have been used in a number of studies directed towards understanding the
Characteristics of the quail and the fieldfare and of some other precocial and altricial species
Species
Egg mass (g)
Body mass at hatching (g)
Adult body mass (g)
Rate constant K (day–1)1
Precocials Quail (Coturnix japonica) Ostrich (Struthio camelus) Red jungle fowl (Gallus gallus) Pheasant (Phasianus colchicus)
9.4a 1390h 35k 29.2e
6.5b 910c 19.8j 17.5c
113b 980001 430j 1230c
0.106c L2 L2 0.031c
Altricials Fieldfare (Turdus pilaris) Starling (Sturnus vulgaris) Pied wagtail (Motacilla alba) Great tit (Parus major) Blue tit (Parus caeruleus) House sparrow (Passer domesticus)
6.3f 7.8e 2.3m 1.6i 1.2i 2.8e
5.1f 5.2b 1.6n 1.4h 1.2c 2.5o
93g 70b 21.6m 18.1c 10.8c 24.5c
0.666c 0.409c H3 0.392c 0.402c 0.420c
Data from: Lilja et al. (2001)a, Ricklefs (1979a)b, Starck and Ricklefs (1998b)c, Bjo¨rnhag (1979)d, Ar and Yom-Tov (1978)e, Blom and Lilja (2004a)f, Lilja (1982)g, This studyh, Bjo¨rklund (1996)i, Jackson and Diamond (1995)j, Saeki and Inou (1979)k, du Preez et al. (1992)l, Cramp (1988)m, calculated from Cramp (1988)n, calculated from Ar and Yom-Tov (1978)o. 1 Rate constant (logistic equation); mean value for each species calculated from studies presented in Starck and Ricklefs (1998a). 2 L denotes lower than average growth rate, du Preez et al. (1992) and Jackson and Diamond (1995). 3 H denotes higher than average growth rates Cramp (1988).
ARTICLE IN PRESS 84
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
anatomical and physiological basis of growth responses (see references above). Even if the other precocial and altricial species used represent incomplete series of embryonic stages they can be useful for comparative purposes.
Morphological measurements In the course of development, the anlagen of the head, brain, eyes, intestines and limbs can easily be identified. Linear measurements of these organ anlagen were taken in the quail and the fieldfare using an image analysis program (Bildanalyssystem-Sweden). A schematic view illustrating how the morphological measurements were made is given in Fig. 2. A majority of these measure-
ments were obtained within the phylotypic period, which has been suggested to start after 18 h of incubation and end after 96 h in the domestic chicken Gallus domesticus (Schneider and Norton, 1979). The data were plotted against somite numbers enabling us to compare the quail and the fieldfare at about the same stages of embryonic development. Following H.H. stage 21 the embryo is fully segmented and hence the somite numbers are arbitrary.
Immunohistochemical procedures Immune staining was performed following a protocol from Lilja et al. (2001). Embryos were embedded in paraffin, sections cut and collected on poly-L-lysin
Fig. 3. Morphological measurements of embryos of quail (m) and fieldfare (n) at early stages of development, H.H. stages 7–12: (a) embryo (length); (b) forebrain (width); (c) anterior part (length); (d) posterior part (length); (e) anterior part relative to embryo length; (f) posterior part relative to embryo length. Quail, n ¼ 15; fieldfare, n ¼ 14.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
coated glass slides. Endogenous peroxidase activity was quenched with 1% hydrogen peroxide in methanol at room temperature for 0.5 h. After blocking with 5% goat serum in TBS (25 mM Tris–HCl, 150 mM NaCl, pH 7.4) for 10 min the sections were incubated overnight at 4 1C with monoclonal antibodies against PAX-7 and MyHC (1:15 dilution of stock solution with 5% goat serum in TBS). Primary antibodies (PAX-7 and MF20) were obtained from DSHB, University of Iowa, USA. After washing in TBS the secondary biotinylated antimouse antibody (1:200 dilution of stock solution with 5% goat serum in TBS) was applied and incubated 1 h at 4 1C. After washing in TBS the streptavidin-HRP complex (ABC, Vectastain) was applied and incubated 1 h at 4 1C. After final washing in TBS the HRP activity was then detected in the presence of 0.023% hydrogen peroxidase and 0.1% diaminobenzidine (DAB) in 0.05 M Tris–HCl (pH 7.6). For whole mount immune staining the fixed and quenched (3% hydrogen peroxide in methanol at room temperature for 1 h) embryos were incubated in 10% goat serum in 50 mM TBS plus 1% Triton X-100 (TBST) for 1 h, and with primary monoclonal antibodies against PAX-7 and MyHC (1:100 dilution of
Table 2.
85
stock solution with 10% goat serum in TBST) at 4 1C overnight. After washing in TBST the embryos were incubated at 4 1C overnight with the secondary biotinylated antibody (1:400 dilution of stock solution with 10% goat serum in TBST). After washing in TBST they were then incubated at 4 1C overnight with streptavidinHRP complex. After final washing in TBST and equilibration with DAB in 0.05 M Tris–HCl (pH 7.6) the HRP reaction was performed by adding H2O2 at a final concentration of 0.023%.
Statistical analysis Morphological differences between the quail and the fieldfare were tested with analyses of covariance (ANCOVA) when slopes were homogeneous. Species was used as a fixed factor and the number of somites as a continuous covariate. To control for simultaneous testing of measures from the same embryo we adjusted the a-values with Holmes correction for simultaneous tests within an experiment group. Table-wide a-value ¼ 0.05 with Holmes correction value (Neter et al., 1996).
Morphological differences between embryos of the quail and the fieldfare
Morphological character
Homogeneity of slopes df
Species
F-value
p-Value
df
F-value
p-Value
0.08 103 13.5 17.5
0.771 o0.001 0.0017 o0.001
Early stages (H.H. stages 7–12) Embryo (length) Anterior part (length) Posterior part (length) Forebrain (width) Anterior part relative to embryo length Posterior part relative to body length
1, 1, 1, 1, 1, 1,
13 14 17 15 13 13
1.18 0.84 3.28 4.42 33.1 23.9
0.296 0.374 0.0877 0.0529 o0.001 o0.001
1, 1, 1, 1,
Later stages (H.H. stages 13–25) Head (length) Optic cup (diameter) Midbrain (height) Midbrain (length) Midbrain height relative to head length Midbrain length relative to head length Optic cup diameter relative to head length
1, 1, 1, 1, 1, 1, 1,
29 30 27 28 27 28 29
2.88 16.6 13.0 14.2 0.03 6.65 17.6
0.101 o0.001 0.0012 o0.001 0.876 0.0155 o0.001
1, 30
11.1
1, 28
16.7
o0.001
1, 8
40.2
o0.001
(H.H stages 9–16) Gut closure (distance of gut closure progression, anteriorly to posteriorly) Distance between lateral folds
1, 7
0.77
0.408
1, 12
7.97
0.0154
Within species Quail, fore limbs vs. hind limbs (length) Fieldfare, fore limbs vs. hind limbs (length)
1, 12 1, 12
0.71 0.41
0.417 0.533
14 15 18 16
1, 13 1, 13
0.93 8.30
0.0023
0.351 0.0129
Note: Differences were tested with analysis of covariance when slopes were homogeneous. Species was used as fixed factor and the number of somites as a continuous covariate.
ARTICLE IN PRESS 86
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Results The growth rates of the quail, fieldfare and the other precocial and altricial species differ considerably, as shown in Table 1. The rate constant presented for the fieldfare is one of the highest that can be found in the
literature, in contrast to the low rate constant for the quail. The different growth rates were associated with different patterns of embryonic development in the quail and the fieldfare as shown by the morphological data and the pattern of expression of muscle specific protein in the somites.
Fig. 4. Embryos of quail (left) and fieldfare (right) at early stages showing different degrees of progression in the development of the anterior and posterior parts (2 2), i.e. the development of the head, brain and eyes vs. the development of the trunk: (a) three somites, H.H. stages 7–8; (b) five somites, H.H. stages 8–9; (c) 10 somites, H.H. stage 10; (d) 14 somites, H.H. stages 11–12. Scale bar: 1 mm.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Morphological measurements The morphological data were compared at early stages (H.H. stage 7 to H.H. stage 12) and at later stages (H.H. stage 13 and onwards) of embryonic development. During the early stages of development embryos of the quail and fieldfare were of approximately the same absolute size, as shown in Fig. 3a and Table 2. However, the size of the anterior part and forebrain differed between the two species, on both an absolute and a relative basis. These components were significantly smaller in the fieldfare than in the quail (po0:001, ANCOVA, Table 2); in contrast, the posterior part was significantly larger (po0:01, ANCOVA, Table 2). These differences are illustrated in Figs. 3b–f, 4 and 5. The different patterns of anterior and posterior development were followed by different patterns of embryonic development during the later stages. From about 20 somites and onwards, the absolute size of the head, and both the absolute and relative size of the midbrain and optic cup were significantly larger in the quail than in the fieldfare (po0:01, ANCOVA, Table 2). These differences are shown in Figs. 6 and 7. For comparative purposes embryos of the pheasant, red jungle fowl, starling, blue tit, great tit, house sparrow and pied wagtail are presented in Fig. 8. Furthermore, quail and fieldfare displayed different patterns of development of the anlagen of the proximal intestine, i.e. the foregut, as shown in Fig. 9. The closure of this intestinal fold proceeds anteriorly to posteriorly, i.e. from the anterior intestinal portal towards the hindgut. This process was initiated significantly earlier
87
in the fieldfare than in the quail (po0:001, ANCOVA, Table 2). This difference is also illustrated in Fig. 10. From a purely descriptive point of view it was evident that the pattern of development of other structures, e.g. the fore and hind limb buds, also differed between the quail and fieldfare during the later stages of development (H.H. stages 18–25). This is illustrated in Fig. 11 together with comparative observations from the ostrich. In the fieldfare, the fore limb buds were significantly larger than the hind limb buds (po0:05, ANCOVA, Table 2). In the quail, we were unable to detect any size differences between the fore and hind limb buds. However, in the ostrich the hind limb buds appeared to be considerably larger than the fore limb buds. Overall, the results showed that the morphology of the quail and the fieldfare varied markedly during embryonic development. The anlagen of the head, brain and eyes were larger in the quail than in the fieldfare. In contrast, development of the gut was more advanced in the fieldfare than in the quail.
PAX-7 and MyHC expression The expression of PAX-7 and MyHC is shown in Figs. 12 and 13. We compared the pattern of PAX-7 expression and the number of somites positive for MyHC with corresponding observations in the quail (Lilja et al., 2001). At stages H.H. 12–13 no somite was positive for MyHC. MyHC expression was, however, clearly visible in the heart. At stages H.H. 14–15 the most cranial somites were positive for MyHC. By stage H.H. 17
Fig. 5. Cross sections of an embryo of quail (left) and fieldfare (right) at an early stage of development, 10 somites, H.H. stage 10, showing different degrees of progression in the development of the forebrain, neural tube and heart: (a) forebrain through optic vesicles; (b) ventricular region of the heart; (c) sinoatrial region of the heart; (d) last somite at midgut level. Scale bar: 1 mm.
ARTICLE IN PRESS 88
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Fig. 6. Morphological measurements of embryos of quail (m) and fieldfare (n) at later stages of development, H.H. stages 13–25. From H.H. stage 21 and onwards somite numbers are arbitrary: (a) head (length); (b) optic cup (diameter); (c) midbrain (height); (d) midbrain (length); (e) midbrain height relative to head length; (f) midbrain length relative to head length; (g) optic cup diameter relative to head length. Quail, n ¼ 33; fieldfare, n ¼ 20.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
89
Fig. 7. Embryos of quail (left) and fieldfare (right) at later stages of development showing differences in the size of the midbrain (n) and eye (m): (a) 24 somites, H.H. stage 15; (b) H.H. stage 18; (c) H.H. stage 22; (d) H.H. stage 25. Scale bars: 1 mm (a–c), 2 mm (d).
(approximately 31 somites), the number of somites positive for MyHC differed significantly between the fieldfare and the quail. In the fieldfare, an average of 22 somites (n ¼ 8, SD72.0) was positive for MyHC compared to 13 (n ¼ 16, SD71.3) in the quail. Clearly,
these observations underscore different rates of myotome formation, i.e. heterochrony. With regard to the pattern of PAX-7 expression we could not detect any significant difference between the two species at any stage of development. The expression of PAX-7 was
ARTICLE IN PRESS 90
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
confined to the segmental plate mesoderm and the dermamyotome prior to myotome formation. In slightly older embryos, PAX-7 was also expressed in myotomes and myoblast cells migrating and forming limb and trunk muscle precursors, as shown in Fig. 12. These findings confirm and extend earlier observations on the pattern of PAX-7 expression in the quail (Lilja et al., 2001).
Discussion Our data revealed that the different morphologies at hatching, which characterize precocial and altricial neonates, were associated with different patterns of embryonic development in the quail and the fieldfare. This was apparent both at the early and at the later stages of development, i.e. during the phylotypic period, even though these stages usually are said to be highly conserved. During the early stages of development the size of the anterior part, especially the forebrain, was relatively larger in the quail than in the fieldfare. In contrast, the size of the posterior part was relatively larger in the fieldfare. This difference was also evident in slightly older embryos. It was accompanied by a notably larger midbrain and optic cup in the quail than in the fieldfare. As a result the polarity of the embryo varied markedly suggesting differential rates of anterior and posterior development in fast and slow growing bird species. This suggestion is also supported by data showing that the closure of the foregut was initiated earlier in the fieldfare than in the quail. Avian embryology has traditionally been biased towards the embryology of the domestic chicken, e.g. Hamburger and Hamilton’s (1951) A series of normal stages in the development of the chick embryo. Normal stages in the development of the embryo of altricial bird species are almost nonexistent in the literature (Yamasaki and Tonosaki, 1988) and only a few comparative studies of early embryonic development of precocial and altricial bird species can be found (Vaugien, 1949; Daniel, 1957). Vaugien (1949) and Daniel (1957) compared embryonic development of the redwing (Turdus iliacus) and the starling, two altricial bird species with high postnatal growth rates, with that of the domestic chicken, a precocial bird species with a low postnatal growth rate. They found that the brain and eyes developed earlier in the domestic chicken than in the other two species. Vaugien (1949) concluded, moreover, that the only difference between nidicolous birds (remaining in the nest for a time after hatching) and nidifugous birds (leaving the nest shortly after hatching) was the relative growth of the brain and the optic lobes. Fig. 8. Embryos of a variety of precocial and altricial species at later stages of development: (a) pheasant (precocial), H.H. stage 19 (left), H.H. stage 23 (right); (b) red jungle fowl (precocial), H.H. stage 19 (left), H.H. stage 24 (right); (c) starling (altricial), H.H. stage 20 (left), H.H. stage 24 (right); (d) blue tit (altricial), H.H. stage 19 (left), H.H. stage 21 (right); (e) great tit (altricial), H.H. stage 21 (left), H.H. stage 24 (right); (f) great tit (altricial), H.H. stage 25 (Hubrecht collection); (g) house sparrow (altricial), H.H. stage 18 (Hubrecht collection); (h) pied wagtail (altricial), H.H. stage 22 (Hubrecht collection). Scale bars: 1 mm (h), 2 mm (a–g).
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
91
Fig. 9. Morphological measurements of embryos of quail and fieldfare at later stages of development, H.H. stages 13–25. From H.H. stage 21 and onwards somite numbers are arbitrary. (a) Distance between lateral folds: (m) quail; (n) fieldfare. (b) Gut closure (distance of gut closure progression, anteriorly to posteriorly): (m) quail; (n) fieldfare. (c) Quail limb buds (length): (m) forelimbs; (n) hind limbs. (d) Fieldfare limb buds (length): (m) forelimbs; (n) hind limbs.). Quail, n ¼ 35; fieldfare, n ¼ 25.
However, Daniel (1957) also found that the anlage of the digestive tract appeared 6–12 h earlier in the redwing than in the domestic chicken and that the heart of the redwing was at a more advanced stage of development. These results are in close agreement with our data and lend further support to the suggestion that fast and slow growing bird species exhibit differential rates of anterior and posterior development. Most likely these differences arise at stages prior to somitogenesis. Maybe they can be linked to differences in the time at which cells emerge from the primitive streak along the anterioposterior axis and/or to differences in the timing of HOX-gene activation. Conclusions concerning such relationships have to await further investigation. Those different rates of anterior and posterior development can, however, be viewed as a resource allocation trade-off between ‘‘supply’’ and ‘‘demand’’ organs showing, moreover, that competition among body parts in development may act as a guiding signal for shaping patterns of development in the embryo. Furthermore, from these results it can be inferred that embryonic development is at least in part constrained by postnatal growth rate, so that any useful increase in assimilation can only be accomplished by a change in the pattern of organ development.
A division of the various organs of the body into ‘‘supply’’ and ‘‘demand’’ organs might appear illogical because growth, development and survival are dependent upon the function of all organs. Nevertheless, it is possible to make at least one clear distinction between these two groups of organs: the ‘‘supply’’ organs are ultimately necessary to fulfill the nutritional demands of the growing animal whereas the development of the ‘‘demand’’ organs can be adapted to different functional needs. The latter is reflected at early embryonic stages by the circumstance that the organs for locomotion displayed different patterns of development in the quail, fieldfare and ostrich. In the fieldfare, the forelimbs were significantly larger than the hind limbs. In the quail, we were unable to detect any size difference between the limbs. However, in the ostrich the hind limbs appeared to be considerably larger than the forelimbs. Similarly, Richardson (1999) used the literature (Parker, 1891) and compared the kiwi (Apteryx australis) and the bat (Rousettus amplexicadatus). The kiwi has relatively small forelimbs and large hind limbs at all stages. By contrast, in the bat the forelimb is large relative to the size of the hind limb at all of the stages examined. This is also the condition for marsupial embryos where the forelimbs are extremely well developed in comparison with the
ARTICLE IN PRESS 92
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Fig. 10. Embryos of quail (left) and fieldfare (right) at early and later stages of development showing closure of the gut tube, lateral endodermal folds (indicated by the arrow n): (a) 14 somites, H.H. stage 11; (b) 21 somites, H.H. stage 14; (c) 16 somites, H.H. stage 12, cross section through the midgut (MG). Scale bars: 1 mm (a–b), 200 mm (c).
hind limbs as shown by Hill and Hill (1955), Smith (2001) and others. Certainly, these different patterns of limb development illustrate different functional demands and suggest, moreover, that selection for yet another late ontogenetic character may produce significant changes in early developmental mechanisms. The latter hypothesis is further supported by the observation that the fieldfare and the quail displayed different patterns of expression of muscle specific protein in the somites. By stage H.H. 17 (approximately 31 somites) the number of somites positive for MyHC was 22 in the fieldfare in comparison with 13 in the quail, suggesting heterochrony in myotome formation. Fate maps obtained from quail-chick chimaeras show, moreover, that the myoblasts from somite numbers 12–22 are those that make up the muscles in the fore limbs and thorax (Gumpel-Pinot, 1984). Similarly, in the quail the brachial somites displayed heterochrony in myotome formation as a result of long-term selection for high and low growth rate, respectively (Lilja et al., 2001). With regard to the pattern of PAX-7 expression we were unable to detect any differences between the fieldfare and the quail at any stage of development.
Fig. 11. Embryos of quail, fieldfare and ostrich at later stages of development showing different patterns of limb-bud development: (a) H.H. stage 20, quail (left) and fieldfare (right); (b) H.H. stage 24, quail (left) and fieldfare (right); (c) H.H. stage 25, quail (left) and ostrich (right). Scale bars: 1 mm (a); 2 mm (b); 3 mm (c).
However, our results confirm and extend earlier observations that PAX-7 is expressed in myotomes and myoblast cells migrating and forming limb and trunk muscle precursors (Kawakami et al., 1997; Lilja et al., 2001), thus suggesting that this protein plays an important role in the development of the limb and trunk muscles. Overall, our findings are in agreement with the prediction that selection for late ontogenetic characteristics, such as the size of ‘‘supply’’ and ‘‘demand’’ organs, which characterize the neonates of slowly growing precocial bird species and more rapidly growing altricial ones, may indeed affect early embryonic development. This leads us to the conclusion that growth rate is of fundamental importance for the patterning of avian embryonic development and, moreover, that the degree of conservation at a phylotypic stage has been overestimated. It also appears that this comparative system provides excellent opportunities to test hypotheses about heterochrony.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
93
References
Fig. 12. Fieldfare embryos at early and later stages of development showing MyHC expression: (a) 15 somites, H.H. stage 12, ventral aspect showing MyHC expression in the heart; (b) 15 somites, H.H. stage 12, dorsal aspect showing absence of MyHC expression in the somites; (c) 23 somites, H.H. stage 14, dorsal aspect showing MyHC expression in the most cranial somites; (d) approximately 31 somites, H.H. stage 17, MyHC expression in the cervical and thoracic somites. Scale bars: 500 mm (a–c), 1 mm (d).
Acknowledgements Special thanks are due to H.L. Marks at the University of Georgia, USA, for the quail eggs; P. Jensen at The Swedish University of Agricultural Sciences for the red jungle fowl eggs; J. Narraway for access to the collections at the Hubrecht Laboratory of the International Embryological Institute in Utrecht, The Netherlands. Thanks are also due to L. Olsson for comments on an earlier version of this manuscript. This study was financially supported by Kalmar University, Va¨xjo¨ University, and the Lenander Foundation.
Fig. 13. Cross section through the wing bud region of a fieldfare embryo at a late stage of development, H.H. stage 24, showing MyHC and PAX-7 expression: (a) PAX-7 expression in the neural tube (NT), dermatome and myotome (DM), and in migrating muscle precursor cells (MP) forming trunk and limb muscles; (b) MyHC expression in the myotome (M). Scale bars: 500 mm.
Alberts, B., Bray, D., Lewis, D., Raff, M., Roberts, K., Watson, J.D., 1994. Molecular Biology of the Cell, third ed. Garland, New York. Ar, A., Yom-Tov, Y., 1978. The evolution of parental care in birds. Evolution 32, 655–669. Bjo¨rklund, M., 1996. Similarity in growth among Great tits (Parus major) and Blue tits (P. caeruleus). Biol. J. Linn. Soc. 58, 343–355. Bjo¨rnhag, G., 1979. Growth in newly hatched birds. Swed. J. Agric. Res. 9, 121–125. Blom, J., Lilja, C., 2004a. A comparative study of growth, skeletal development and eggshell composition in some species of birds. J. Zool. Lond. 262, 361–369. Blom, J., Lilja, C., 2004b. Patterning of embryonic development in birds. Proc. ICVM-7, J. Morphol. 260, 279. Bober, E., Franz, T., Arnold, H.-H., Gruss, P., Tremblay, P., 1994. Pax-3 is required for the development of limb muscles: a possible role for the migration of dermomyotomal progenitor cells. Development 120, 603–612. Christ, B., Jacob, H., Jacob, M., 1978. On the formation of myotomes in avian embryos. An experimental and scanning electron microscopic study. Experientia 34, 514–516. Clum, N.J., McClearn, D.K., Barbato, G.F., 1995. Comparative embryonic development in chickens with different patterns of postnatal-growth. Growth Dev. Aging 59, 129–138. Coutinho, L.L., Morris, J., Marks, H.L., Buhr, J., Ivarie, B., 1993. Delayed somite formation in a quail line exhibiting myofiber hyperplasia is accompanied by delayed expression of myogenic regulatory factors and myosin heavy chain. Development 117, 563–569. Cramp, S., 1988. Handbook of the Birds of the Western Palearctic, Vol 5. Oxford University Press, Oxford, pp. 454–471. Daniel, J.C., 1957. An embryological comparison of the domestic fowl and the red-winged blackbird. Auk 74, 340–358. Darwin, C., 1859. The Origin of Species by Means of Natural Selection. John Murray, London. de Beer, G.R., 1951. Embryos and Ancestors. Clarendon Press, Oxford. Duboule, D., 1994. Temporal colinearity and the phylotypic period: a basis for the stability of a vertebrate bauplan and the evolution of morphogenesis through heterochrony. Dev. Suppl., 135–142. du Preez, J.J., Jarvis, M.J.F., Capatos, D., de Kock, J., 1992. A note on growth curves for the ostrich (Struthio camelus). Anim. Prod. 54, 150–152. Gould, S.J., 1977. Ontogeny and Phylogeny. Belknap Press of Harvard University Press, Cambridge, MA. Gould, S.J., 1992. Ontogeny and phylogeny — revisited and reunited. BioEssays 14, 275–279. Goulding, M., Lumsden, A., Paguette, A.J., 1994. Regulation of Pax-3 expression in the dermomyotome and its role in muscle development. Development 120, 957–971. Gumpel-Pinot, M., 1984. Muscle and skeleton of limbs and body wall. In: Douarin, N.M., MacLaren, A. (Eds.),
ARTICLE IN PRESS 94
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Chimaeras in developmental biology. Academic Press, London, pp. 281–310. Haeckel, E., 1891. Anthropogenie oder Entwicklungsgeschichte des Menschen. Engelmann, Leipzig. Hamburger, V., Hamilton, H.L., 1951. A series of normal stages in the development of the chick embryo. J. Morphol. 88, 49–92. Hill, J.P., Hill, W.C.O., 1955. The growth stages of the pouch young of the native cat (Dasyurus viverrinus) together with observations on the anatomy of the new born young. Trans. Zool. Soc. Lond. 28, 349–453. Jackson, S.J., Diamond, J.M., 1995. Ontogenetic development of gut function, growth, and metabolism in a wild bird, the red jungle fowl. Am. J. Physiol. 38, R1163–R1173. Jostes, B., Walther, C., Gruss, P., 1990. The murine paired box gene, Pax-7, is expressed specifically during the development of the nervous and muscular system. Mech. Dev. 33, 27–37. Katanbaf, M.N., Dunnington, E.A., Siegel, P.B., 1988. Allomorphic relationship from hatching to 56 days in parental lines and F1 crosses of chickens selected 27 generations for high or low body-weight. Growth Dev. Aging 52, 11–21. Kawakami, A., Kimura-Kawakami, M., Nomura, T., Fujisawa, H., 1997. Distribution of PAX6 and PAX7 proteins suggest their involvement in both early and late phases of chick brain development. Mech. Dev. 66, 119–130. Klingenberg, C.P., 1998. Heterochrony and allometry: the analysis of evolutionary change in ontogeny. Biol. Rev. 73, 79–123. Konarzewski, M., Starck, J.M., 2000. Effects of food shortage and oversupply on energy utilization, histology, and function of the gut in nestling song thrushes (Turdus philomelos). Physiol. Biochem. Zool. 73, 416–427. Konarzewski, M., Kozlowski, J., Ziolko, K., 1989. Optimal allocation of energy to growth of alimentary tract in birds. Funct. Ecol. 3, 589–596. Konarzewski, M., Kowalczyk, T., Swierubska, T., Lewonzuk, B., 1996. Effect of short-term feed restriction. Realimentation and over feeding on growth of song thrush (Turdus philomelos) nestlings. Funct. Ecol. 10, 97–105. Lilja, C., 1982. Postnatal growth and organ development in the fieldfare and the jackdaw (Turdus pilaris and Corvus monedula). Growth 46, 367–387. Lilja, C., 1983. A comparative study of postnatal growth and organ development in some species of birds. Growth 47, 317–339. Lilja, C., Blom, J., 1999. Comparative studies of early embryonic development in Quail Coturnix coturnix japonica with different patterns of postnatal growth. Acta Ornith. 34, 159–164. Lilja, C., 1997. On the pattern of organ growth in the Common Tern (Sterna hirundo). Growth Dev. Aging 55, 219–224. Lilja, C., Marks, H.L., 1991. Changes in organ growth pattern associated with long-term selection for high growth rate in quail. Growth Dev. Aging 55, 219–224. Lilja, C., Sperber, I., Marks, H.L., 1985. Postnatal growth and organ development in Japanese quail selected for high growth rate. Growth 49, 51–62.
Lilja, C., Blom, J., Marks, H.L., 2001. A comparative study of embryonic development of Japanese quail selected for different patterns of postnatal growth. Zoology 104, 115–122. McKinney, M.L., McNamara, K.J., 1991. Heterochrony, the Evolution of Ontogeny. Plenum, New York. Neff, M., 1972. Untersuchungen u¨ber das embryonale und postembryonale Organwachstum bei Vogelarten mit verschiedenem Ontogenesemodus. Rev. Suisse Zool. 79, 1471–1597. Neter, J., Kutner, M.H., Nachtsheim, C.J., Wasserman, W., 1996. Applied Linear Statistical Models, fourth ed. McGraw-Hill/Irwin. Nice, M.M., 1962. Development of behaviour in precocial birds. Trans. Linn. Soc. NY 8, 1–211. Ordahl, C.P., LeDouarin, N., 1992. Two myogenic lineages within the developing somite. Development 114, 339–353. Parker, T.J., 1891. Observations on the anatomy and development of Apteryx. Philos. Trans. R. Soc. Lond. B 182, 25–134. Portmann, A., 1955. Die postembryonale Entwicklung der Vo¨gel als Evolutionsproblem. Proceedings of the 11th International Ornithology Congress, pp. 138–151. Raff, R.A., 1994. Developmental mechanisms in the evolution of animal form: origins and evolvability of body plans. In: Bengtson, S. (Ed.), Early Life on Earth. Columbia University Press, New York, pp. 489–500. Raff, R.A., 1996. The Shape of Life: Genes, Development and the Evolution of Animal Form. University of Chicago Press, Chicago. Raff, R.A., Wray, G.A., 1989. Heterochrony: developmental mechanisms and evolutionary results. J. Evol. Biol. 2, 409–434. Richardson, M.K., 1995. Heterochrony and the phylotypic period. Dev. Biol. 172, 412–421. Richardson, M.K., 1999. Vertebrate evolution: the developmental origins of adult variation. BioEssays 21, 604–613. Richardson, M.K., Hanken, J., Goonerate, M.L., Pieau, C., Raynaud, A., Selwood, L., Wright, G.M., 1997. There is no highly conserved stage in the vertebrates: implications for current theories of evolution and development. Anat. Embryol. 196, 91–106. Ricklefs, R.E., 1968. Patterns of growth in birds. Ibis 110, 419–451. Ricklefs, R.E., 1973. Patterns of growth in birds. II. Growth rate and mode of development. Ibis 115, 177–201. Ricklefs, R.E., 1979a. Patterns of growth in birds. V. A comparative study of development in the Starling, Common Tern and Japanese Quail. Auk 96, 10–30. Ricklefs, R.E., 1979b. Adaptation, constraint, and compromise in avian postnatal development. Biol. Rev. 54, 269–290. Ricklefs, R.E., Starck, J.M., 1998. Embryonic growth and development. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 31–58. Ricklefs, R.E., Starck, J.M., Konarzewski, M., 1998. Internal constraints on growth in birds. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 266–287. Saeki, Y., Inou, Y., 1979. Body growth, egg production, broodiness, age at first egg and egg size in red jungle fowls, and an attempt at their genetic analyses by the reciprocal crossing with White Leghorns. Jpn. Poult. Sci. 16, 121–126. Schmidt, K., Starck, J.M., 2004. Developmental variability during early embryonic development of zebra fish, Danio rerio. J. Exp. Zool. (Mol. Dev. Evol.) 302B, 446–457. Schneider, B.F., Norton, S., 1979. Equivalent ages in rat, mouse and chick embryos. Teratology 19, 273–278. Slack, F., Ruvkun, G., 1997. Temporal pattern formation by heterochronic genes. Annu. Rev. Genet. 31, 611–634. Slack, J.M.W., Holland, P., Graham, C.F., 1993. The zootype and the phylotypic stage. Nature 361, 490–492. Smith, K.K., 1997. Comparative patterns of craniofacial development in eutherian and metatherian mammals. Evolution 51, 1663–1678. Smith, K.K., 2001. Heterochrony revisited: the evolution of developmental sequences. Biol. J. Linn. Soc. 73, 169–186. Smith, K.K., 2002. Sequence heterochrony and the evolution of development. J. Morphol. 252, 82–97.
95
Starck, J.M., 1993. Evolution of avian ontogenies. Curr. Ornithol. 10, 275–366. Starck, J.M., Ricklefs, R.E., 1998a. Patterns of development: the altricial–precocial spectrum. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 3–30. Starck, J.M., Ricklefs, R.E., 1998b. Avian growth rate data set. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 381–423. Vaugien, L., 1949. Relation biome´trique interspecifique dans la croissance des oiseaux. C. R. Acad. Sci. Paris 228, 206–207. Von Baer, K.E., 1828. Entwicklungsgeschichte der Tiere, Beobachtung und Reflexion. Borntra¨ger, Ko¨nigsberg. Wallace, A., 1997. The Origin of Animal Body Form. Cambridge University Press, Cambridge. Wolpert, L., 1991. The Triumph of the Embryo. Oxford University Press, Oxford. Yamasaki, M., Tonosaki, A., 1988. Developmental stages of the society finch, Lonchura striata var. domestica. Dev. Growth Diff. 30, 515–542.
ZOOLOGY Zoology 108 (2005) 81–95 www.elsevier.de/zool
A comparative study of embryonic development of some bird species with different patterns of postnatal growth Jonas Blom, Clas Lilja Department of Biology and Environmental Science, Kalmar University, Kalmar SE-391 82, Sweden Received 14 January 2005; accepted 23 February 2005
Abstract Some studies show that birds with high postnatal growth rates (e.g. altricial species) are characterized by a rapid early development of ‘‘supply’’ organs, such as digestive organs. Birds with low postnatal growth rates (e.g. precocial species) exhibit a slower early development of these organs and a more rapid early development of other ‘‘demand’’ organs, such as brain, muscles, skeleton and feathers. To test whether these differences can be traced back to early embryonic development and whether they can be associated with changes in developmental timing, i.e. heterochrony, we compared embryos of the precocial quail and the altricial fieldfare, two bird species with low and high postnatal growth rates, respectively. We used classical staging techniques that use developmental landmarks to categorize embryonic maturity as well as morphological measurements. These techniques were combined with immune detection of muscle specific proteins in the somites. Our data showed that the anlagen of the head, brain and eyes develop earlier in the quail than in the fieldfare in contrast to the gut which develops earlier in the fieldfare than in the quail. Our data also showed that the quail and the fieldfare displayed different rates of myotome formation in the somites which contribute to muscle formation in the limbs and thorax. We believe these observations are connected with important differences in neonatal characteristics, such as the size of the brain, eyes, organs for locomotion and digestion. This leads us to the conclusion that selection for late ontogenetic characteristics can alter early embryonic development and that growth rate is of fundamental importance for the patterning of avian embryonic development. It also appears that this comparative system offers excellent opportunities to test hypotheses about heterochrony. r 2005 Elsevier GmbH. All rights reserved. Keywords: Altricial species; Precocial species; Embryonic development; Myotome formation; Heterochrony; PAX-7
Introduction Early embryonic development has traditionally been viewed as invariant within vertebrate taxa (Von Baer, 1828; Darwin, 1859; Haeckel, 1891, reviewed in Gould, 1977; Wallace, 1997). It has been suggested that most or all vertebrate embryos pass through a virtually identical Corresponding author. Tel.: +46 480 446170; fax: +46 480 447305.
E-mail address: [email protected] (C. Lilja). 0944-2006/$ - see front matter r 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.zool.2005.02.001
conserved stage, the phylotypic stage (reviewed by Raff, 1994, 1996; Richardson et al., 1997). This view has been the common consensus in textbooks over the last century (Alberts et al., 1994). Embryonic resemblance at the tail bud stage has been linked with a conserved pattern of developmental gene expression, i.e. the zootype (Slack et al., 1993; Slack and Ruvkun, 1997). It has been argued that specific differences between vertebrate embryos arise largely through modifications at later stages of development (Wolpert, 1991; Slack et al., 1993;
ARTICLE IN PRESS 82
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Alberts et al., 1994; Duboule, 1994; Ricklefs and Starck, 1998; reviewed in Richardson et al., 1997). Such modifications may be a result of allometric growth and/or heterochrony, changes in developmental timing (de Beer, 1951; Gould, 1977; Raff and Wray, 1989; McKinney and McNamara, 1991; Gould, 1992; Duboule, 1994; Richardson, 1995; Klingenberg, 1998; Smith, 2001). While there is a large body of data dealing with heterochrony at later stages of development, actual data about developmental timing during early to midembryonic stages are scarce. A few studies, however, have presented evidence on significant variation between early vertebrate embryos (e.g. Richardson, 1995; Richardson et al., 1997; Smith, 1997; Lilja and Blom, 1999; Richardson, 1999; Lilja et al., 2001; Smith, 2001, 2002; Schmidt and Starck, 2004). These studies show that adult variation can be generated at a variety of embryonic stages. It has long been recognized that growth rate and size are significantly correlated in birds (Ricklefs, 1968, 1973, 1979b; Bjo¨rnhag, 1979; Starck, 1993; Ricklefs et al., 1998). Among birds of similar size, however, species deviations from this relationship can sometimes be significant. Much of this deviation is related to the degree of precocity of the chick. At the one extreme are precocial species (Nice, 1962) whose young hatch covered with down, eyes open, organs of locomotion fairly well developed, and able to feed on their own. At the other extreme are altricial species (Nice, 1962) whose young hatch blind, naked and with less well-developed organs of locomotion, but with highly developed organs of digestion and a dependence on parental care (Portmann, 1955; Neff, 1972; Lilja, 1983; Starck and Ricklefs, 1998a; Fig. 1). On average altricial bird species grow three to four times more rapidly than precocial species (Ricklefs, 1968, 1973, 1979a, b; Bjo¨rnhag, 1979; Starck, 1993; Ricklefs et al., 1998). Despite extensive work on avian growth and development, less attention has been paid to developmental differences which characterize different bird taxa. It has
Fig. 1. The precocial quail (left) and the altricial fieldfare (right) at the time of hatching.
been suggested, however, that growth rate may be of fundamental importance for generating changes in the pattern of organ development (Lilja et al., 1985; Katanbaf et al., 1988; Lilja and Marks, 1991; Clum et al., 1995; Lilja et al., 2001; Blom and Lilja, 2004a, b). It appears that individuals and species with higher than average postnatal growth rates are those that allocate a large share of the early growth to rapid development of ‘‘supply’’ organs, such as the digestive organs. Such a large early investment in these organs may have been at the expense of growth directed to ‘‘demand’’ organs, such as brain, muscles, skeleton and feathers. From these and other studies (Lilja, 1983; Konarzewski et al., 1989; Jackson and Diamond, 1995; Konarzewski et al., 1996; Lilja, 1997; Ricklefs et al., 1998; Konarzewski and Starck, 2000) it can be inferred that the ‘‘supply’’ organs usually function close to their maximum rate and that any increase in assimilation can only be accomplished by a change in the organ growth pattern. Hence, it follows that this restriction may limit the range of morphological variation that can be produced to the patterns permitted by ‘‘supply’’ and ‘‘demand’’ organ relationships. In view of these considerations, we assumed that different patterns of postnatal growth are established during embryonic stages, so that embryonic development forms part of a wider complex of ‘‘supply’’ and ‘‘demand’’ organ relationships. We tested this prediction by comparing embryonic development in birds with very different postnatal growth patterns. We used embryos of the precocial quail (Coturnix japonica) and the altricial fieldfare (Turdus pilaris), two species with low and high growth rates, respectively. In particular, we tested whether late ontogenetic neonatal characteristics, such as large and small brains, eyes, and organs of locomotion and digestion may be established at early embryonic stages, i.e. during the phylotypic period, even though these stages are usually considered to be highly conserved. We used classical staging techniques that use developmental landmarks to categorize embryonic maturity as well as morphological measurements of those ‘‘supply’’ and ‘‘demand’’ organs in development. These techniques were combined with immune detection of PAX-7 (paired box homeotic gene) and myosin heavy chain (MyHC), two proteins essential for the patterning of muscle cell formation. PAX-7 is expressed in the segmental plate and the dermamyotome prior to myotome formation (Jostes et al., 1990; Bober et al., 1994; Goulding et al., 1994; Kawakami et al., 1997; Lilja et al., 2001). In slightly older embryos, PAX-7 is also expressed in myotomes and myoblast cells migrating and forming limb and trunk muscle precursors (Kawakami et al., 1997; Lilja et al., 2001). As soon as the myoblast cells from the myotome begin to fuse they are post-mitotic, terminally differentiated muscle cells characterized by expressing muscle specific proteins, such as
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
83
developmental timing should be associated with either an earlier or later occurrence of this marker of late muscle cell differentiation, provided the initial somite number was identical.
Material and methods Embryos Fig. 2. Schematic figure showing how the morphological measurements were made. (Left) (a) Head length (distance from isthmus to anterior-most part of telencephalon); (b) midbrain length (distance from isthmus to mesencephalon/ diencephalon junction); (c) midbrain height (distance from the dorsal-most to ventral-most part of mesencephalon); (d) Optic cup (diameter); (e) bud (wing and leg) length (distance from the midline at the basal bud border to apex of bud curve, distal-most part). (Upper right) (f) Embryo length (distance from the anterior-most part of the embryo proper to the posterior part of hensens node); (g) forebrain (width); (h) anterior part (distance from the anterior-most part of the embryo proper to 1st somite); posterior part (length of the embryo less the length of the anterior part). (Lower right) Gut tube, development of lateral folds: (i) distance between lateral folds; (j) gut closure (distance of gut closure progression, anteriorly to posteriorly).
MyHC. Hence, we used MyHC as a late marker of muscle cell differentiation (Christ et al., 1978; Ordahl and LeDouarin, 1992; Coutinho et al., 1993; Lilja et al., 2001). We predicted, therefore, that differences in Table 1.
Quail eggs were obtained from the Southern Regional Poultry Genetics Laboratory at the University of Georgia and stored at 7–10 1C for less than a week. Incubation was conducted at 37 1C in a humidified chamber, embryos collected, fixed in 4% paraformaldehyde, dehydrated in alcohol and then staged according to Hamburger and Hamilton (1951). Eggs of the fieldfare were incubated in the nests by the parent birds. Embryos were then collected, fixed, dehydrated and staged as above. A few embryos of some other precocial species (ostrich Struthio camelus, red jungle fowl Gallus gallus, pheasant Phasianus colchicus) and altricial species (starling Sturnus vulgaris, pied wagtail Motacilla alba, great tit Parus major, blue tit Parus carruleus, house sparrow Passer domesticus) were presented for comparative purposes. They were obtained from various sources: The Swedish University of Agricultural Sciences, The Hubrecht collection at the Netherlands Institute of Developmental Embryology, commercial breeders, and in the field. The quail and the fieldfare (Fig. 1) have been used in a number of studies directed towards understanding the
Characteristics of the quail and the fieldfare and of some other precocial and altricial species
Species
Egg mass (g)
Body mass at hatching (g)
Adult body mass (g)
Rate constant K (day–1)1
Precocials Quail (Coturnix japonica) Ostrich (Struthio camelus) Red jungle fowl (Gallus gallus) Pheasant (Phasianus colchicus)
9.4a 1390h 35k 29.2e
6.5b 910c 19.8j 17.5c
113b 980001 430j 1230c
0.106c L2 L2 0.031c
Altricials Fieldfare (Turdus pilaris) Starling (Sturnus vulgaris) Pied wagtail (Motacilla alba) Great tit (Parus major) Blue tit (Parus caeruleus) House sparrow (Passer domesticus)
6.3f 7.8e 2.3m 1.6i 1.2i 2.8e
5.1f 5.2b 1.6n 1.4h 1.2c 2.5o
93g 70b 21.6m 18.1c 10.8c 24.5c
0.666c 0.409c H3 0.392c 0.402c 0.420c
Data from: Lilja et al. (2001)a, Ricklefs (1979a)b, Starck and Ricklefs (1998b)c, Bjo¨rnhag (1979)d, Ar and Yom-Tov (1978)e, Blom and Lilja (2004a)f, Lilja (1982)g, This studyh, Bjo¨rklund (1996)i, Jackson and Diamond (1995)j, Saeki and Inou (1979)k, du Preez et al. (1992)l, Cramp (1988)m, calculated from Cramp (1988)n, calculated from Ar and Yom-Tov (1978)o. 1 Rate constant (logistic equation); mean value for each species calculated from studies presented in Starck and Ricklefs (1998a). 2 L denotes lower than average growth rate, du Preez et al. (1992) and Jackson and Diamond (1995). 3 H denotes higher than average growth rates Cramp (1988).
ARTICLE IN PRESS 84
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
anatomical and physiological basis of growth responses (see references above). Even if the other precocial and altricial species used represent incomplete series of embryonic stages they can be useful for comparative purposes.
Morphological measurements In the course of development, the anlagen of the head, brain, eyes, intestines and limbs can easily be identified. Linear measurements of these organ anlagen were taken in the quail and the fieldfare using an image analysis program (Bildanalyssystem-Sweden). A schematic view illustrating how the morphological measurements were made is given in Fig. 2. A majority of these measure-
ments were obtained within the phylotypic period, which has been suggested to start after 18 h of incubation and end after 96 h in the domestic chicken Gallus domesticus (Schneider and Norton, 1979). The data were plotted against somite numbers enabling us to compare the quail and the fieldfare at about the same stages of embryonic development. Following H.H. stage 21 the embryo is fully segmented and hence the somite numbers are arbitrary.
Immunohistochemical procedures Immune staining was performed following a protocol from Lilja et al. (2001). Embryos were embedded in paraffin, sections cut and collected on poly-L-lysin
Fig. 3. Morphological measurements of embryos of quail (m) and fieldfare (n) at early stages of development, H.H. stages 7–12: (a) embryo (length); (b) forebrain (width); (c) anterior part (length); (d) posterior part (length); (e) anterior part relative to embryo length; (f) posterior part relative to embryo length. Quail, n ¼ 15; fieldfare, n ¼ 14.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
coated glass slides. Endogenous peroxidase activity was quenched with 1% hydrogen peroxide in methanol at room temperature for 0.5 h. After blocking with 5% goat serum in TBS (25 mM Tris–HCl, 150 mM NaCl, pH 7.4) for 10 min the sections were incubated overnight at 4 1C with monoclonal antibodies against PAX-7 and MyHC (1:15 dilution of stock solution with 5% goat serum in TBS). Primary antibodies (PAX-7 and MF20) were obtained from DSHB, University of Iowa, USA. After washing in TBS the secondary biotinylated antimouse antibody (1:200 dilution of stock solution with 5% goat serum in TBS) was applied and incubated 1 h at 4 1C. After washing in TBS the streptavidin-HRP complex (ABC, Vectastain) was applied and incubated 1 h at 4 1C. After final washing in TBS the HRP activity was then detected in the presence of 0.023% hydrogen peroxidase and 0.1% diaminobenzidine (DAB) in 0.05 M Tris–HCl (pH 7.6). For whole mount immune staining the fixed and quenched (3% hydrogen peroxide in methanol at room temperature for 1 h) embryos were incubated in 10% goat serum in 50 mM TBS plus 1% Triton X-100 (TBST) for 1 h, and with primary monoclonal antibodies against PAX-7 and MyHC (1:100 dilution of
Table 2.
85
stock solution with 10% goat serum in TBST) at 4 1C overnight. After washing in TBST the embryos were incubated at 4 1C overnight with the secondary biotinylated antibody (1:400 dilution of stock solution with 10% goat serum in TBST). After washing in TBST they were then incubated at 4 1C overnight with streptavidinHRP complex. After final washing in TBST and equilibration with DAB in 0.05 M Tris–HCl (pH 7.6) the HRP reaction was performed by adding H2O2 at a final concentration of 0.023%.
Statistical analysis Morphological differences between the quail and the fieldfare were tested with analyses of covariance (ANCOVA) when slopes were homogeneous. Species was used as a fixed factor and the number of somites as a continuous covariate. To control for simultaneous testing of measures from the same embryo we adjusted the a-values with Holmes correction for simultaneous tests within an experiment group. Table-wide a-value ¼ 0.05 with Holmes correction value (Neter et al., 1996).
Morphological differences between embryos of the quail and the fieldfare
Morphological character
Homogeneity of slopes df
Species
F-value
p-Value
df
F-value
p-Value
0.08 103 13.5 17.5
0.771 o0.001 0.0017 o0.001
Early stages (H.H. stages 7–12) Embryo (length) Anterior part (length) Posterior part (length) Forebrain (width) Anterior part relative to embryo length Posterior part relative to body length
1, 1, 1, 1, 1, 1,
13 14 17 15 13 13
1.18 0.84 3.28 4.42 33.1 23.9
0.296 0.374 0.0877 0.0529 o0.001 o0.001
1, 1, 1, 1,
Later stages (H.H. stages 13–25) Head (length) Optic cup (diameter) Midbrain (height) Midbrain (length) Midbrain height relative to head length Midbrain length relative to head length Optic cup diameter relative to head length
1, 1, 1, 1, 1, 1, 1,
29 30 27 28 27 28 29
2.88 16.6 13.0 14.2 0.03 6.65 17.6
0.101 o0.001 0.0012 o0.001 0.876 0.0155 o0.001
1, 30
11.1
1, 28
16.7
o0.001
1, 8
40.2
o0.001
(H.H stages 9–16) Gut closure (distance of gut closure progression, anteriorly to posteriorly) Distance between lateral folds
1, 7
0.77
0.408
1, 12
7.97
0.0154
Within species Quail, fore limbs vs. hind limbs (length) Fieldfare, fore limbs vs. hind limbs (length)
1, 12 1, 12
0.71 0.41
0.417 0.533
14 15 18 16
1, 13 1, 13
0.93 8.30
0.0023
0.351 0.0129
Note: Differences were tested with analysis of covariance when slopes were homogeneous. Species was used as fixed factor and the number of somites as a continuous covariate.
ARTICLE IN PRESS 86
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Results The growth rates of the quail, fieldfare and the other precocial and altricial species differ considerably, as shown in Table 1. The rate constant presented for the fieldfare is one of the highest that can be found in the
literature, in contrast to the low rate constant for the quail. The different growth rates were associated with different patterns of embryonic development in the quail and the fieldfare as shown by the morphological data and the pattern of expression of muscle specific protein in the somites.
Fig. 4. Embryos of quail (left) and fieldfare (right) at early stages showing different degrees of progression in the development of the anterior and posterior parts (2 2), i.e. the development of the head, brain and eyes vs. the development of the trunk: (a) three somites, H.H. stages 7–8; (b) five somites, H.H. stages 8–9; (c) 10 somites, H.H. stage 10; (d) 14 somites, H.H. stages 11–12. Scale bar: 1 mm.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Morphological measurements The morphological data were compared at early stages (H.H. stage 7 to H.H. stage 12) and at later stages (H.H. stage 13 and onwards) of embryonic development. During the early stages of development embryos of the quail and fieldfare were of approximately the same absolute size, as shown in Fig. 3a and Table 2. However, the size of the anterior part and forebrain differed between the two species, on both an absolute and a relative basis. These components were significantly smaller in the fieldfare than in the quail (po0:001, ANCOVA, Table 2); in contrast, the posterior part was significantly larger (po0:01, ANCOVA, Table 2). These differences are illustrated in Figs. 3b–f, 4 and 5. The different patterns of anterior and posterior development were followed by different patterns of embryonic development during the later stages. From about 20 somites and onwards, the absolute size of the head, and both the absolute and relative size of the midbrain and optic cup were significantly larger in the quail than in the fieldfare (po0:01, ANCOVA, Table 2). These differences are shown in Figs. 6 and 7. For comparative purposes embryos of the pheasant, red jungle fowl, starling, blue tit, great tit, house sparrow and pied wagtail are presented in Fig. 8. Furthermore, quail and fieldfare displayed different patterns of development of the anlagen of the proximal intestine, i.e. the foregut, as shown in Fig. 9. The closure of this intestinal fold proceeds anteriorly to posteriorly, i.e. from the anterior intestinal portal towards the hindgut. This process was initiated significantly earlier
87
in the fieldfare than in the quail (po0:001, ANCOVA, Table 2). This difference is also illustrated in Fig. 10. From a purely descriptive point of view it was evident that the pattern of development of other structures, e.g. the fore and hind limb buds, also differed between the quail and fieldfare during the later stages of development (H.H. stages 18–25). This is illustrated in Fig. 11 together with comparative observations from the ostrich. In the fieldfare, the fore limb buds were significantly larger than the hind limb buds (po0:05, ANCOVA, Table 2). In the quail, we were unable to detect any size differences between the fore and hind limb buds. However, in the ostrich the hind limb buds appeared to be considerably larger than the fore limb buds. Overall, the results showed that the morphology of the quail and the fieldfare varied markedly during embryonic development. The anlagen of the head, brain and eyes were larger in the quail than in the fieldfare. In contrast, development of the gut was more advanced in the fieldfare than in the quail.
PAX-7 and MyHC expression The expression of PAX-7 and MyHC is shown in Figs. 12 and 13. We compared the pattern of PAX-7 expression and the number of somites positive for MyHC with corresponding observations in the quail (Lilja et al., 2001). At stages H.H. 12–13 no somite was positive for MyHC. MyHC expression was, however, clearly visible in the heart. At stages H.H. 14–15 the most cranial somites were positive for MyHC. By stage H.H. 17
Fig. 5. Cross sections of an embryo of quail (left) and fieldfare (right) at an early stage of development, 10 somites, H.H. stage 10, showing different degrees of progression in the development of the forebrain, neural tube and heart: (a) forebrain through optic vesicles; (b) ventricular region of the heart; (c) sinoatrial region of the heart; (d) last somite at midgut level. Scale bar: 1 mm.
ARTICLE IN PRESS 88
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Fig. 6. Morphological measurements of embryos of quail (m) and fieldfare (n) at later stages of development, H.H. stages 13–25. From H.H. stage 21 and onwards somite numbers are arbitrary: (a) head (length); (b) optic cup (diameter); (c) midbrain (height); (d) midbrain (length); (e) midbrain height relative to head length; (f) midbrain length relative to head length; (g) optic cup diameter relative to head length. Quail, n ¼ 33; fieldfare, n ¼ 20.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
89
Fig. 7. Embryos of quail (left) and fieldfare (right) at later stages of development showing differences in the size of the midbrain (n) and eye (m): (a) 24 somites, H.H. stage 15; (b) H.H. stage 18; (c) H.H. stage 22; (d) H.H. stage 25. Scale bars: 1 mm (a–c), 2 mm (d).
(approximately 31 somites), the number of somites positive for MyHC differed significantly between the fieldfare and the quail. In the fieldfare, an average of 22 somites (n ¼ 8, SD72.0) was positive for MyHC compared to 13 (n ¼ 16, SD71.3) in the quail. Clearly,
these observations underscore different rates of myotome formation, i.e. heterochrony. With regard to the pattern of PAX-7 expression we could not detect any significant difference between the two species at any stage of development. The expression of PAX-7 was
ARTICLE IN PRESS 90
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
confined to the segmental plate mesoderm and the dermamyotome prior to myotome formation. In slightly older embryos, PAX-7 was also expressed in myotomes and myoblast cells migrating and forming limb and trunk muscle precursors, as shown in Fig. 12. These findings confirm and extend earlier observations on the pattern of PAX-7 expression in the quail (Lilja et al., 2001).
Discussion Our data revealed that the different morphologies at hatching, which characterize precocial and altricial neonates, were associated with different patterns of embryonic development in the quail and the fieldfare. This was apparent both at the early and at the later stages of development, i.e. during the phylotypic period, even though these stages usually are said to be highly conserved. During the early stages of development the size of the anterior part, especially the forebrain, was relatively larger in the quail than in the fieldfare. In contrast, the size of the posterior part was relatively larger in the fieldfare. This difference was also evident in slightly older embryos. It was accompanied by a notably larger midbrain and optic cup in the quail than in the fieldfare. As a result the polarity of the embryo varied markedly suggesting differential rates of anterior and posterior development in fast and slow growing bird species. This suggestion is also supported by data showing that the closure of the foregut was initiated earlier in the fieldfare than in the quail. Avian embryology has traditionally been biased towards the embryology of the domestic chicken, e.g. Hamburger and Hamilton’s (1951) A series of normal stages in the development of the chick embryo. Normal stages in the development of the embryo of altricial bird species are almost nonexistent in the literature (Yamasaki and Tonosaki, 1988) and only a few comparative studies of early embryonic development of precocial and altricial bird species can be found (Vaugien, 1949; Daniel, 1957). Vaugien (1949) and Daniel (1957) compared embryonic development of the redwing (Turdus iliacus) and the starling, two altricial bird species with high postnatal growth rates, with that of the domestic chicken, a precocial bird species with a low postnatal growth rate. They found that the brain and eyes developed earlier in the domestic chicken than in the other two species. Vaugien (1949) concluded, moreover, that the only difference between nidicolous birds (remaining in the nest for a time after hatching) and nidifugous birds (leaving the nest shortly after hatching) was the relative growth of the brain and the optic lobes. Fig. 8. Embryos of a variety of precocial and altricial species at later stages of development: (a) pheasant (precocial), H.H. stage 19 (left), H.H. stage 23 (right); (b) red jungle fowl (precocial), H.H. stage 19 (left), H.H. stage 24 (right); (c) starling (altricial), H.H. stage 20 (left), H.H. stage 24 (right); (d) blue tit (altricial), H.H. stage 19 (left), H.H. stage 21 (right); (e) great tit (altricial), H.H. stage 21 (left), H.H. stage 24 (right); (f) great tit (altricial), H.H. stage 25 (Hubrecht collection); (g) house sparrow (altricial), H.H. stage 18 (Hubrecht collection); (h) pied wagtail (altricial), H.H. stage 22 (Hubrecht collection). Scale bars: 1 mm (h), 2 mm (a–g).
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
91
Fig. 9. Morphological measurements of embryos of quail and fieldfare at later stages of development, H.H. stages 13–25. From H.H. stage 21 and onwards somite numbers are arbitrary. (a) Distance between lateral folds: (m) quail; (n) fieldfare. (b) Gut closure (distance of gut closure progression, anteriorly to posteriorly): (m) quail; (n) fieldfare. (c) Quail limb buds (length): (m) forelimbs; (n) hind limbs. (d) Fieldfare limb buds (length): (m) forelimbs; (n) hind limbs.). Quail, n ¼ 35; fieldfare, n ¼ 25.
However, Daniel (1957) also found that the anlage of the digestive tract appeared 6–12 h earlier in the redwing than in the domestic chicken and that the heart of the redwing was at a more advanced stage of development. These results are in close agreement with our data and lend further support to the suggestion that fast and slow growing bird species exhibit differential rates of anterior and posterior development. Most likely these differences arise at stages prior to somitogenesis. Maybe they can be linked to differences in the time at which cells emerge from the primitive streak along the anterioposterior axis and/or to differences in the timing of HOX-gene activation. Conclusions concerning such relationships have to await further investigation. Those different rates of anterior and posterior development can, however, be viewed as a resource allocation trade-off between ‘‘supply’’ and ‘‘demand’’ organs showing, moreover, that competition among body parts in development may act as a guiding signal for shaping patterns of development in the embryo. Furthermore, from these results it can be inferred that embryonic development is at least in part constrained by postnatal growth rate, so that any useful increase in assimilation can only be accomplished by a change in the pattern of organ development.
A division of the various organs of the body into ‘‘supply’’ and ‘‘demand’’ organs might appear illogical because growth, development and survival are dependent upon the function of all organs. Nevertheless, it is possible to make at least one clear distinction between these two groups of organs: the ‘‘supply’’ organs are ultimately necessary to fulfill the nutritional demands of the growing animal whereas the development of the ‘‘demand’’ organs can be adapted to different functional needs. The latter is reflected at early embryonic stages by the circumstance that the organs for locomotion displayed different patterns of development in the quail, fieldfare and ostrich. In the fieldfare, the forelimbs were significantly larger than the hind limbs. In the quail, we were unable to detect any size difference between the limbs. However, in the ostrich the hind limbs appeared to be considerably larger than the forelimbs. Similarly, Richardson (1999) used the literature (Parker, 1891) and compared the kiwi (Apteryx australis) and the bat (Rousettus amplexicadatus). The kiwi has relatively small forelimbs and large hind limbs at all stages. By contrast, in the bat the forelimb is large relative to the size of the hind limb at all of the stages examined. This is also the condition for marsupial embryos where the forelimbs are extremely well developed in comparison with the
ARTICLE IN PRESS 92
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Fig. 10. Embryos of quail (left) and fieldfare (right) at early and later stages of development showing closure of the gut tube, lateral endodermal folds (indicated by the arrow n): (a) 14 somites, H.H. stage 11; (b) 21 somites, H.H. stage 14; (c) 16 somites, H.H. stage 12, cross section through the midgut (MG). Scale bars: 1 mm (a–b), 200 mm (c).
hind limbs as shown by Hill and Hill (1955), Smith (2001) and others. Certainly, these different patterns of limb development illustrate different functional demands and suggest, moreover, that selection for yet another late ontogenetic character may produce significant changes in early developmental mechanisms. The latter hypothesis is further supported by the observation that the fieldfare and the quail displayed different patterns of expression of muscle specific protein in the somites. By stage H.H. 17 (approximately 31 somites) the number of somites positive for MyHC was 22 in the fieldfare in comparison with 13 in the quail, suggesting heterochrony in myotome formation. Fate maps obtained from quail-chick chimaeras show, moreover, that the myoblasts from somite numbers 12–22 are those that make up the muscles in the fore limbs and thorax (Gumpel-Pinot, 1984). Similarly, in the quail the brachial somites displayed heterochrony in myotome formation as a result of long-term selection for high and low growth rate, respectively (Lilja et al., 2001). With regard to the pattern of PAX-7 expression we were unable to detect any differences between the fieldfare and the quail at any stage of development.
Fig. 11. Embryos of quail, fieldfare and ostrich at later stages of development showing different patterns of limb-bud development: (a) H.H. stage 20, quail (left) and fieldfare (right); (b) H.H. stage 24, quail (left) and fieldfare (right); (c) H.H. stage 25, quail (left) and ostrich (right). Scale bars: 1 mm (a); 2 mm (b); 3 mm (c).
However, our results confirm and extend earlier observations that PAX-7 is expressed in myotomes and myoblast cells migrating and forming limb and trunk muscle precursors (Kawakami et al., 1997; Lilja et al., 2001), thus suggesting that this protein plays an important role in the development of the limb and trunk muscles. Overall, our findings are in agreement with the prediction that selection for late ontogenetic characteristics, such as the size of ‘‘supply’’ and ‘‘demand’’ organs, which characterize the neonates of slowly growing precocial bird species and more rapidly growing altricial ones, may indeed affect early embryonic development. This leads us to the conclusion that growth rate is of fundamental importance for the patterning of avian embryonic development and, moreover, that the degree of conservation at a phylotypic stage has been overestimated. It also appears that this comparative system provides excellent opportunities to test hypotheses about heterochrony.
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
93
References
Fig. 12. Fieldfare embryos at early and later stages of development showing MyHC expression: (a) 15 somites, H.H. stage 12, ventral aspect showing MyHC expression in the heart; (b) 15 somites, H.H. stage 12, dorsal aspect showing absence of MyHC expression in the somites; (c) 23 somites, H.H. stage 14, dorsal aspect showing MyHC expression in the most cranial somites; (d) approximately 31 somites, H.H. stage 17, MyHC expression in the cervical and thoracic somites. Scale bars: 500 mm (a–c), 1 mm (d).
Acknowledgements Special thanks are due to H.L. Marks at the University of Georgia, USA, for the quail eggs; P. Jensen at The Swedish University of Agricultural Sciences for the red jungle fowl eggs; J. Narraway for access to the collections at the Hubrecht Laboratory of the International Embryological Institute in Utrecht, The Netherlands. Thanks are also due to L. Olsson for comments on an earlier version of this manuscript. This study was financially supported by Kalmar University, Va¨xjo¨ University, and the Lenander Foundation.
Fig. 13. Cross section through the wing bud region of a fieldfare embryo at a late stage of development, H.H. stage 24, showing MyHC and PAX-7 expression: (a) PAX-7 expression in the neural tube (NT), dermatome and myotome (DM), and in migrating muscle precursor cells (MP) forming trunk and limb muscles; (b) MyHC expression in the myotome (M). Scale bars: 500 mm.
Alberts, B., Bray, D., Lewis, D., Raff, M., Roberts, K., Watson, J.D., 1994. Molecular Biology of the Cell, third ed. Garland, New York. Ar, A., Yom-Tov, Y., 1978. The evolution of parental care in birds. Evolution 32, 655–669. Bjo¨rklund, M., 1996. Similarity in growth among Great tits (Parus major) and Blue tits (P. caeruleus). Biol. J. Linn. Soc. 58, 343–355. Bjo¨rnhag, G., 1979. Growth in newly hatched birds. Swed. J. Agric. Res. 9, 121–125. Blom, J., Lilja, C., 2004a. A comparative study of growth, skeletal development and eggshell composition in some species of birds. J. Zool. Lond. 262, 361–369. Blom, J., Lilja, C., 2004b. Patterning of embryonic development in birds. Proc. ICVM-7, J. Morphol. 260, 279. Bober, E., Franz, T., Arnold, H.-H., Gruss, P., Tremblay, P., 1994. Pax-3 is required for the development of limb muscles: a possible role for the migration of dermomyotomal progenitor cells. Development 120, 603–612. Christ, B., Jacob, H., Jacob, M., 1978. On the formation of myotomes in avian embryos. An experimental and scanning electron microscopic study. Experientia 34, 514–516. Clum, N.J., McClearn, D.K., Barbato, G.F., 1995. Comparative embryonic development in chickens with different patterns of postnatal-growth. Growth Dev. Aging 59, 129–138. Coutinho, L.L., Morris, J., Marks, H.L., Buhr, J., Ivarie, B., 1993. Delayed somite formation in a quail line exhibiting myofiber hyperplasia is accompanied by delayed expression of myogenic regulatory factors and myosin heavy chain. Development 117, 563–569. Cramp, S., 1988. Handbook of the Birds of the Western Palearctic, Vol 5. Oxford University Press, Oxford, pp. 454–471. Daniel, J.C., 1957. An embryological comparison of the domestic fowl and the red-winged blackbird. Auk 74, 340–358. Darwin, C., 1859. The Origin of Species by Means of Natural Selection. John Murray, London. de Beer, G.R., 1951. Embryos and Ancestors. Clarendon Press, Oxford. Duboule, D., 1994. Temporal colinearity and the phylotypic period: a basis for the stability of a vertebrate bauplan and the evolution of morphogenesis through heterochrony. Dev. Suppl., 135–142. du Preez, J.J., Jarvis, M.J.F., Capatos, D., de Kock, J., 1992. A note on growth curves for the ostrich (Struthio camelus). Anim. Prod. 54, 150–152. Gould, S.J., 1977. Ontogeny and Phylogeny. Belknap Press of Harvard University Press, Cambridge, MA. Gould, S.J., 1992. Ontogeny and phylogeny — revisited and reunited. BioEssays 14, 275–279. Goulding, M., Lumsden, A., Paguette, A.J., 1994. Regulation of Pax-3 expression in the dermomyotome and its role in muscle development. Development 120, 957–971. Gumpel-Pinot, M., 1984. Muscle and skeleton of limbs and body wall. In: Douarin, N.M., MacLaren, A. (Eds.),
ARTICLE IN PRESS 94
J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Chimaeras in developmental biology. Academic Press, London, pp. 281–310. Haeckel, E., 1891. Anthropogenie oder Entwicklungsgeschichte des Menschen. Engelmann, Leipzig. Hamburger, V., Hamilton, H.L., 1951. A series of normal stages in the development of the chick embryo. J. Morphol. 88, 49–92. Hill, J.P., Hill, W.C.O., 1955. The growth stages of the pouch young of the native cat (Dasyurus viverrinus) together with observations on the anatomy of the new born young. Trans. Zool. Soc. Lond. 28, 349–453. Jackson, S.J., Diamond, J.M., 1995. Ontogenetic development of gut function, growth, and metabolism in a wild bird, the red jungle fowl. Am. J. Physiol. 38, R1163–R1173. Jostes, B., Walther, C., Gruss, P., 1990. The murine paired box gene, Pax-7, is expressed specifically during the development of the nervous and muscular system. Mech. Dev. 33, 27–37. Katanbaf, M.N., Dunnington, E.A., Siegel, P.B., 1988. Allomorphic relationship from hatching to 56 days in parental lines and F1 crosses of chickens selected 27 generations for high or low body-weight. Growth Dev. Aging 52, 11–21. Kawakami, A., Kimura-Kawakami, M., Nomura, T., Fujisawa, H., 1997. Distribution of PAX6 and PAX7 proteins suggest their involvement in both early and late phases of chick brain development. Mech. Dev. 66, 119–130. Klingenberg, C.P., 1998. Heterochrony and allometry: the analysis of evolutionary change in ontogeny. Biol. Rev. 73, 79–123. Konarzewski, M., Starck, J.M., 2000. Effects of food shortage and oversupply on energy utilization, histology, and function of the gut in nestling song thrushes (Turdus philomelos). Physiol. Biochem. Zool. 73, 416–427. Konarzewski, M., Kozlowski, J., Ziolko, K., 1989. Optimal allocation of energy to growth of alimentary tract in birds. Funct. Ecol. 3, 589–596. Konarzewski, M., Kowalczyk, T., Swierubska, T., Lewonzuk, B., 1996. Effect of short-term feed restriction. Realimentation and over feeding on growth of song thrush (Turdus philomelos) nestlings. Funct. Ecol. 10, 97–105. Lilja, C., 1982. Postnatal growth and organ development in the fieldfare and the jackdaw (Turdus pilaris and Corvus monedula). Growth 46, 367–387. Lilja, C., 1983. A comparative study of postnatal growth and organ development in some species of birds. Growth 47, 317–339. Lilja, C., Blom, J., 1999. Comparative studies of early embryonic development in Quail Coturnix coturnix japonica with different patterns of postnatal growth. Acta Ornith. 34, 159–164. Lilja, C., 1997. On the pattern of organ growth in the Common Tern (Sterna hirundo). Growth Dev. Aging 55, 219–224. Lilja, C., Marks, H.L., 1991. Changes in organ growth pattern associated with long-term selection for high growth rate in quail. Growth Dev. Aging 55, 219–224. Lilja, C., Sperber, I., Marks, H.L., 1985. Postnatal growth and organ development in Japanese quail selected for high growth rate. Growth 49, 51–62.
Lilja, C., Blom, J., Marks, H.L., 2001. A comparative study of embryonic development of Japanese quail selected for different patterns of postnatal growth. Zoology 104, 115–122. McKinney, M.L., McNamara, K.J., 1991. Heterochrony, the Evolution of Ontogeny. Plenum, New York. Neff, M., 1972. Untersuchungen u¨ber das embryonale und postembryonale Organwachstum bei Vogelarten mit verschiedenem Ontogenesemodus. Rev. Suisse Zool. 79, 1471–1597. Neter, J., Kutner, M.H., Nachtsheim, C.J., Wasserman, W., 1996. Applied Linear Statistical Models, fourth ed. McGraw-Hill/Irwin. Nice, M.M., 1962. Development of behaviour in precocial birds. Trans. Linn. Soc. NY 8, 1–211. Ordahl, C.P., LeDouarin, N., 1992. Two myogenic lineages within the developing somite. Development 114, 339–353. Parker, T.J., 1891. Observations on the anatomy and development of Apteryx. Philos. Trans. R. Soc. Lond. B 182, 25–134. Portmann, A., 1955. Die postembryonale Entwicklung der Vo¨gel als Evolutionsproblem. Proceedings of the 11th International Ornithology Congress, pp. 138–151. Raff, R.A., 1994. Developmental mechanisms in the evolution of animal form: origins and evolvability of body plans. In: Bengtson, S. (Ed.), Early Life on Earth. Columbia University Press, New York, pp. 489–500. Raff, R.A., 1996. The Shape of Life: Genes, Development and the Evolution of Animal Form. University of Chicago Press, Chicago. Raff, R.A., Wray, G.A., 1989. Heterochrony: developmental mechanisms and evolutionary results. J. Evol. Biol. 2, 409–434. Richardson, M.K., 1995. Heterochrony and the phylotypic period. Dev. Biol. 172, 412–421. Richardson, M.K., 1999. Vertebrate evolution: the developmental origins of adult variation. BioEssays 21, 604–613. Richardson, M.K., Hanken, J., Goonerate, M.L., Pieau, C., Raynaud, A., Selwood, L., Wright, G.M., 1997. There is no highly conserved stage in the vertebrates: implications for current theories of evolution and development. Anat. Embryol. 196, 91–106. Ricklefs, R.E., 1968. Patterns of growth in birds. Ibis 110, 419–451. Ricklefs, R.E., 1973. Patterns of growth in birds. II. Growth rate and mode of development. Ibis 115, 177–201. Ricklefs, R.E., 1979a. Patterns of growth in birds. V. A comparative study of development in the Starling, Common Tern and Japanese Quail. Auk 96, 10–30. Ricklefs, R.E., 1979b. Adaptation, constraint, and compromise in avian postnatal development. Biol. Rev. 54, 269–290. Ricklefs, R.E., Starck, J.M., 1998. Embryonic growth and development. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 31–58. Ricklefs, R.E., Starck, J.M., Konarzewski, M., 1998. Internal constraints on growth in birds. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution
ARTICLE IN PRESS J. Blom, C. Lilja / Zoology 108 (2005) 81–95
Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 266–287. Saeki, Y., Inou, Y., 1979. Body growth, egg production, broodiness, age at first egg and egg size in red jungle fowls, and an attempt at their genetic analyses by the reciprocal crossing with White Leghorns. Jpn. Poult. Sci. 16, 121–126. Schmidt, K., Starck, J.M., 2004. Developmental variability during early embryonic development of zebra fish, Danio rerio. J. Exp. Zool. (Mol. Dev. Evol.) 302B, 446–457. Schneider, B.F., Norton, S., 1979. Equivalent ages in rat, mouse and chick embryos. Teratology 19, 273–278. Slack, F., Ruvkun, G., 1997. Temporal pattern formation by heterochronic genes. Annu. Rev. Genet. 31, 611–634. Slack, J.M.W., Holland, P., Graham, C.F., 1993. The zootype and the phylotypic stage. Nature 361, 490–492. Smith, K.K., 1997. Comparative patterns of craniofacial development in eutherian and metatherian mammals. Evolution 51, 1663–1678. Smith, K.K., 2001. Heterochrony revisited: the evolution of developmental sequences. Biol. J. Linn. Soc. 73, 169–186. Smith, K.K., 2002. Sequence heterochrony and the evolution of development. J. Morphol. 252, 82–97.
95
Starck, J.M., 1993. Evolution of avian ontogenies. Curr. Ornithol. 10, 275–366. Starck, J.M., Ricklefs, R.E., 1998a. Patterns of development: the altricial–precocial spectrum. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 3–30. Starck, J.M., Ricklefs, R.E., 1998b. Avian growth rate data set. In: Starck, J.M., Ricklefs, R.E. (Eds.), Avian Growth and Development. Evolution Within the Altricial–Precocial Spectrum. Oxford University Press, Oxford, pp. 381–423. Vaugien, L., 1949. Relation biome´trique interspecifique dans la croissance des oiseaux. C. R. Acad. Sci. Paris 228, 206–207. Von Baer, K.E., 1828. Entwicklungsgeschichte der Tiere, Beobachtung und Reflexion. Borntra¨ger, Ko¨nigsberg. Wallace, A., 1997. The Origin of Animal Body Form. Cambridge University Press, Cambridge. Wolpert, L., 1991. The Triumph of the Embryo. Oxford University Press, Oxford. Yamasaki, M., Tonosaki, A., 1988. Developmental stages of the society finch, Lonchura striata var. domestica. Dev. Growth Diff. 30, 515–542.