- Email: [email protected]
Uptake of inorganic ions from the maternal circulation during development of the embryo of a viviparous lizard, Sphenomorphus quoyii
Camp.
Biodwm.
Physiol.
Vol.
71A,
pp.
107
10 112,
1982
03CO-9629/82/010107-06$03.00/'0 PergamonPress Ltd
PrmtedinGreatBritam
UPTAKE OF INORGANIC IONS FROM THE MATERNAL CIRCULATION DURING DEVELOPMENT THE EMBRYO OF A VIVIPAROUS LIZARD, SPHENOMORPHUS
OF
QUOYII
JANE THOMPSON*
School of Biological Sciences, University of Sydney, N.S.W. 2006, Australia (Received
7 May 1981)
Inorganic ion content of developing follicles and of whole eggs and separated embryos and sacs of the viviparous lizard, ~p~eno~r~~~s qucyii has been measured. There is a net increase in calcium, sodium and potassium in whole eggs during gestation. Magneand phosphorus content remains constant. The additional ions are incorporated into the developing embryo. Calcium content of the yolk is compared with that of the fowl and other species of reptile.
Abstract-l.
yolk 2. sium 3. 4.
INTRODUCTION
MATERIALS AND Sampling
It has been suggested that the yolk of viviparous reptiles is rich in minerals, particularly calcium, and provides adequate inorganic ions for embryonic growth
Females were collected from a study area 30 km south of Sydney at regular intervals during one breeding season. Lizards were killed with an intra-peritoneal injection of Nembutal within four days of capture and dissected. In non-Dregnant females ovaries were removed and the developing foilicies separated, weighed and dried to constant __.__. weight in a vacuum drier at 25°C. Dried samples were then heaikd in crucibles in a muffle furnace at 420°C for 24 hr to determine the ash weight. In pregnant females, the oviducts were removed and the eggs released by teasing away the oviducts with a pair of fine forceps. Stages studied ranged from immediately after ovulation to full term embryos. One or two whole eggs from each female were used for immediate determination of total dry and ash weight as above. In addition, in later stage samples, after removing the extra-embryonic fluids and membranes, the embryo and yoIk sac were dried and ashed separately.
(Jenkins & Simkiss, 1968). These authors found no increase in the calcium, magnesium or inorganic phosphorus content during development of the egg of the adder, Vipera berus. As far as I am aware, no detailed analyses of changes in inorganic ion content of embryos of any other viviparous reptile have been reported. Clark & Sisken (1956) claimed that there was an increase in total inorganic ion content of eggs of the viviparous snake, Thamnophis sirtalis, however, as pointed out by Shine (1977), the trend is not statisticalIy significant. However, Shine (1977) reported a significant increase in the ash content of the eggs of Ps~li~ec~~s porphyri~cus during development as was also found in the viviparous lizard, ~phe~o~rphus quoyii (Thompson, 1977a). This species has a simple type of placenta (Weekes, 1927) which may be the route for transfer of inorganic ions. Thus, in at least two species, there is evidence for uptake of minerals from the mother during development supplementing minerals supplied in the yolk. In addition, it has been shown in two species of viviparous snake that the placenta is permeable to inorganic ions (Conaway & Fleming, 1960; Hoffman, 1970). In this study some of the minerals which contribute to the increase in total inorganic ion content in the eggs of S. ~uoyii during development were deter-
lnorgunjc
mined. The total calcium, magnesium, sodium and potassium in enlarging follicles, in whole eggs and in separated yolk sacs and embryos at different stages were measured as well as the inorganic phosphorus content of early and near term eggs. * Present address: Zoology Department, National University, P.O. Box 4, Canberra Australia.
METHODS
Australian ACT 2600,
ionanalyses
Analyses of inorganic ions were carried out on ashed samples of follicles, whole eggs and separated embryos and yolk sacs as follows. One ml concentrated HCI was added to the weighed ash sample in a small test tube and heated in a boiling water bath for 1 hr. The heated sample was then filtered through Whatman 541 filter paper (ash-free) into a 10ml (or 5&l for small samples) v&metric flask. The filter paper was rinsed with hot deionised water and the rinsings collected in the volumetric flask. The filter paper wit; any residual particles was then transferred to a small crucible. dried at 60°C and then reashed at 450°C _ in ... a muffle furnace overnight. This treatment removed any particles which were not completely ashed. The reashed sample was then transferred to the original volumetric flask and the solution made up to volume with deionised water. Blanks were also run at the same time using ashed filter papers. Calcium and magnesium were determined by atomic absorption spectrophotometry (Perkin-Elmer Model 303 Atomic Absorption Spectrophotometer). Sodium and potassium were measured by flame photometry (Instrumentation Laboratory Inc., Flame Photometry 343) and inorganic phosphate using the Phosphorus Rapid Stat kit (Pierce, Illinois).
107
JANETHOMPSON 0. 5r
(cl
. .
.
.
0.4l
. i:
l
i .2
*
B
l.
c.0
.
. .
0 I.3 -
.
. . 0. 2>
.
fd) Oi PO -
l
*
* .
. E 0
m
cl! 55 -
*
i
3 t z 2 0.4 io -
l l
.
. Oi!5l
.
0 IOI
240
I
I
400
320
0
Follicle wet weight, mg
,
8
240
320
Follicle wet weight, mg
i 240
I
320
1Magneelum, 400
Follicle wet weight, mg
Fig. I. Changes in the calcium (a), magnesium (b), sodium (c) and potassium (d) content of developing follicles of S. quoyii. The data are combined in Fig. 1 (e) for comparison.
Mineral uptake by lizard embryo Estimationof the age of embryos In captured adult females follicles developed
approx.
synchronously and, during the breeding season, at any one time, pregnant females carried embryos at approximately the same stage of gestation. Therefore the age of embryos was estimated by taking Day 1 as the day on which I first found females which had ovulated, assuming that fertilization took place at ovulation.
RESULTS
Changes in the composition of calcium, magnesium, sodium and potassium in developing follicles are shown in Fig. 1. There was a significant increase in amount of all ions. The relative increase in calcium was greater than for the other measured ions. The whole egg Changes in inorganic ion content of the whole egg are shown in Fig. 2. Total calcium content increased, the most rapid rate of increase being in the last third of the gestation period. Sodium, and potassium also increased but there was no significant change in the amount of magnesium. Total inorganic phosphorus in the. ash of eight eggs collected soon after ovulation was 4.07 + 0.18 mg (X + SEM) compared with 3.87 f 0.26 mg in 8 whole eggs containing embryos at term. The difference is not statistically significant (ti* = 0.64, P > 0.25). 7he embryo and yolk sac To determine whether ions taken up by the whole egg were incorporated into the embryo, changes in the calcium, magnesium, sodium and potassium content of the embryo and yolk sac were measured at different stages of gestation (Fig. 3). The amounts of calcium, sodium and potassium in embryos near term were greater than the amounts of these ions initially present in the yolk. The gains in all three ions were equivalent to the total gains measured in the whole egg. As expected, there was no gain in the amount of magnesium in the embryo. There was a steady decline in the amount of all ions in the yolk, except sodium, where there was a peak at about the time of midgestation. This coincides with the rise in water content of the yolk (Thompson, 1977b, 1982).
DISCUSSION
There is a 21% increase in the ash content of the eggs of S. quoyii during development (Thompson, 1977a). While there may be transplacental flow of inorganic ions in both direction there is thus a net gain in the inorganic ion content of the egg. The only other report of an increase in ash content in a viviparous reptile is for Pseudechis porphyriacus, where the ash content increased by 54% (Shine, 1977). The present study shows that the major part of the increase in total ash content in S. quoyii eggs during development can be attributed to uptake of calcium with a small net gain in sodium and potassium. Furthermore, it has been shown that all of these additional ions are incorporated into the embryo.
109
There has been some discussion in the literature regarding the sources of calcium for developing reptile embryos. Packard et at. (1977), concluded that all of the calcium (and probably magnesium) required by the reptile embryo is present in the egg at the time of ovulation. This conclusion is supported by the findings of a number of authors (Cunnin~am er al., 1939; Bustard & Greenham, 1968; Jenkins & Simkiss, 1968; Bustard et al., 1969; Jenkins, 1975). Packard et al. (1977) suggested that in reptiles there are two fundamentally different means for provision of calcium to the embryo. Embryonic crocodilians and chelonians recover calcium from the egg shell and the yolk does not contain all the calcium necessary for skeletal development (Bustard et al., 1969; Jenkins, 1975). The yolk of chelonians is apparently rich in magnesium, however (Bustard, et al., 1969). In contrast, embryos of snakes and lizards, including some geckos which produce calcareous egg shells, probably obtain all the necessary calcium and magnesium from rich stores present in the yolk alone (Jenkins 8z Simkiss, 1968). In the only study, to my knowledge, of a viviparous species, Jenkins & Simkiss (1968) found no increase in the total quantities of either calcium, phosphorus or magnesium during development of embryos of the snake Vipera berus. They concluded that the yolk was rich enough in ions necessary for skeletal formation and there was no need to postulate a role of the placenta in supplying additional ions. Their findings differ from the results with S. quoyii where there is a definite intake of calcium. It is interesting therefore to compare the concentration of calcium in the yolk of S. quoyii with that in other reptiles. Jenkins & Simkiss (1968) claimed that in comparison with turtles, the calcium content of the yolk of squamates is relatively high. The calcium content of the yolk of a number of species is compared in Table 1. The calcium content of the yolk in S. quoyii is less than reported values for other squamates but higher than that of turtles and chickens. With a reduced amount of calcium in the yolk it may therefore be necessary for additional calcium to be transferred to the embryo via the placenta. This may also be true for sodium and potassium although there are no measurements of these ions in the yolk of any reptile for comparison. Alternatively or in addition, uptake of sodium and potassium may be necessary to enable active transport of water which is taken up during development. The pattern of sodium uptake corresponds to that of water uptake (Thompson, 1977h 1982). Calcium taken up by the embryo may not be used immediately for bone formation. It is known that reptile embryos store calcium as CaCO, in the endolymphatic sacs of the inner ear (Simkiss, 1967; Jenkins & Simkiss, 1968). Obvious white deposits in these sacs were observed in S. quoyii embryos. Thus calcium may be stored and used later for bone formation.
~ck~ow~e~~e~e~rs-I thank Drs Gordon Grigg, Richard Shine and Associate Professor John Simons for their interest and advice. The research was supported by a Commonwealth Postgraduate Research Award. I thank Mrs Wendy Guy for her typing.
JANETHOMPSON
112
Table 1. Calcium content of the yolk of eggs of different species
Species
Calcium mg ‘A of wet weight
Fowl Turtles: Dermorhelys coricacea Thalassoche~ys corticata Pseudem~ls scipta
Snakes : Viper0 berm Thamnophis sauritus
Reference
104
Urist & Schjeide (1961)
94 72 212
Simkiss (1967) Needham (1931) Urist & Schjeide (1961)
959 1400
Simkiss (1967) Dessaur & Fox (1959)
Lizards: Anguis fragihs Lacerta vivipara Hemidactylus frenatus Hemidactylus turcicus S. quoyii
REFERENCES
BUSTARDH. R. & GREENHAM P. (1968) Physical and chemical factors affecting hatchjng in the green sea turtle, Chelonia mydas (L.). Ecology 49, 269-276. BUSTARDH. R., SIMKISSL. & JENKINS N. K. (1969) Some analyses of artificially incubated eggs and hatchlings of green and loggerhead sea turtles. J. Zool., Lond. 158, 311-31s.
CLARKH. & SIXEN B. F. (1956) Nitrogenous excretion by embryos of the viviparous snake Thamnophis s. sirtalis (L.). J. exp. Biol. 33, 384393. CONAWAYC. H. & FLEMINGW. R. (1960) Placental transmission of Na22 and Ir3’ in Natrix. Copeia 196453-55. CUNNINGHAMB., WOODWARDM. W. and PRIDGEN J. (1939) Further studies on incubation of turtle (Mafaclefflys centrata Lat.) eggs. Am. Nat. 73, 28.5-288. DESSAURH. C. & Fox W. (1959) Changes in ovarian foihde composition with plasma levels of snakes during estrus. Am. J. Physics. 197, 360-366. HOFFMANL. H. (1970) Placentation in the Garter Snake, ~hamnophis sirtalis. J. Morph. 131, 57-88.
JENKINSN. K. (1975) Chemical composition of the eggs of the crocodile (Crocodyius novaeguinea). Comp. Biochem. Physiol. 51A, 891-895. JENKINSN. K. & SIMKI~.Y K. (1968) The calcium and.phosphate metabolism of reproducing reptiles with particular reference to the adder (Vipera berus). Comp. Biochem. Physiol. 26, 865-876.
713 916
1500 1100 425
Jenkins Jenkins Jenkins Jenkins
81 Simkiss & Simkiss & Simkiss & Simkiss
(1968) (1968) (1968) (1968)
NEEDHAMJ. (1931) Chemical Embryology. Cambridge University Press, London. PACKARDG. C., TRACY R. C. & ROTH J. J. (1977) The physiologic~ ecology of reptilian eggs and embryos and the evolution of viviparity within the Class Reptilia. Biol. Rev. 52, 71-105. SHINER. (1977) Reproduction in Australian elapid snakes. II. Female reproductive cycles. Aust. J. Zool. 25, 655-666. S1~~rs.s K. (1967) Calcium in reproductive physiology. Chapman & Hall, London. THOMPWNJ. (1977a) Embryo-maternal relationships in a viviparous skink, Sphenomorphus quoyii (Lacertilia: Scincidae) In Reproduction and Evolution. (Edited by CALABY J. H. & TYNDALE-BISCOE C. H.) pp. 279-280. Australian Academy of Science. THOMPSONJ. (1977b) Embryo-maternal relationships in a viviparous lizard, Sphenom~rphus quoyii (Dumerii and Bibronf. Ph.D. Thesis, University of Sydney. 158 pp. THOMPSON J. (1982) A study of the sources of nutrients for embryonic development in a viviparous lizard, Sphenomorphus quoyii. Camp. Biochem Physioi. (In press). URIST M. R. & SCHJEIDEA. 0. (1961) The partition of calcium and protein in the blood of oviparous vertebrates during estrus. J. gen. Physiol. 44, 743-756. WEEKESH. C. (1927) Placentation and other phenomena in the scincid lizard Lygosoma (Him&a) quoyii. Proc. Linn. Sot. N.S.W! 52, 499-554.
Biodwm.
Physiol.
Vol.
71A,
pp.
107
10 112,
1982
03CO-9629/82/010107-06$03.00/'0 PergamonPress Ltd
PrmtedinGreatBritam
UPTAKE OF INORGANIC IONS FROM THE MATERNAL CIRCULATION DURING DEVELOPMENT THE EMBRYO OF A VIVIPAROUS LIZARD, SPHENOMORPHUS
OF
QUOYII
JANE THOMPSON*
School of Biological Sciences, University of Sydney, N.S.W. 2006, Australia (Received
7 May 1981)
Inorganic ion content of developing follicles and of whole eggs and separated embryos and sacs of the viviparous lizard, ~p~eno~r~~~s qucyii has been measured. There is a net increase in calcium, sodium and potassium in whole eggs during gestation. Magneand phosphorus content remains constant. The additional ions are incorporated into the developing embryo. Calcium content of the yolk is compared with that of the fowl and other species of reptile.
Abstract-l.
yolk 2. sium 3. 4.
INTRODUCTION
MATERIALS AND Sampling
It has been suggested that the yolk of viviparous reptiles is rich in minerals, particularly calcium, and provides adequate inorganic ions for embryonic growth
Females were collected from a study area 30 km south of Sydney at regular intervals during one breeding season. Lizards were killed with an intra-peritoneal injection of Nembutal within four days of capture and dissected. In non-Dregnant females ovaries were removed and the developing foilicies separated, weighed and dried to constant __.__. weight in a vacuum drier at 25°C. Dried samples were then heaikd in crucibles in a muffle furnace at 420°C for 24 hr to determine the ash weight. In pregnant females, the oviducts were removed and the eggs released by teasing away the oviducts with a pair of fine forceps. Stages studied ranged from immediately after ovulation to full term embryos. One or two whole eggs from each female were used for immediate determination of total dry and ash weight as above. In addition, in later stage samples, after removing the extra-embryonic fluids and membranes, the embryo and yoIk sac were dried and ashed separately.
(Jenkins & Simkiss, 1968). These authors found no increase in the calcium, magnesium or inorganic phosphorus content during development of the egg of the adder, Vipera berus. As far as I am aware, no detailed analyses of changes in inorganic ion content of embryos of any other viviparous reptile have been reported. Clark & Sisken (1956) claimed that there was an increase in total inorganic ion content of eggs of the viviparous snake, Thamnophis sirtalis, however, as pointed out by Shine (1977), the trend is not statisticalIy significant. However, Shine (1977) reported a significant increase in the ash content of the eggs of Ps~li~ec~~s porphyri~cus during development as was also found in the viviparous lizard, ~phe~o~rphus quoyii (Thompson, 1977a). This species has a simple type of placenta (Weekes, 1927) which may be the route for transfer of inorganic ions. Thus, in at least two species, there is evidence for uptake of minerals from the mother during development supplementing minerals supplied in the yolk. In addition, it has been shown in two species of viviparous snake that the placenta is permeable to inorganic ions (Conaway & Fleming, 1960; Hoffman, 1970). In this study some of the minerals which contribute to the increase in total inorganic ion content in the eggs of S. ~uoyii during development were deter-
lnorgunjc
mined. The total calcium, magnesium, sodium and potassium in enlarging follicles, in whole eggs and in separated yolk sacs and embryos at different stages were measured as well as the inorganic phosphorus content of early and near term eggs. * Present address: Zoology Department, National University, P.O. Box 4, Canberra Australia.
METHODS
Australian ACT 2600,
ionanalyses
Analyses of inorganic ions were carried out on ashed samples of follicles, whole eggs and separated embryos and yolk sacs as follows. One ml concentrated HCI was added to the weighed ash sample in a small test tube and heated in a boiling water bath for 1 hr. The heated sample was then filtered through Whatman 541 filter paper (ash-free) into a 10ml (or 5&l for small samples) v&metric flask. The filter paper was rinsed with hot deionised water and the rinsings collected in the volumetric flask. The filter paper wit; any residual particles was then transferred to a small crucible. dried at 60°C and then reashed at 450°C _ in ... a muffle furnace overnight. This treatment removed any particles which were not completely ashed. The reashed sample was then transferred to the original volumetric flask and the solution made up to volume with deionised water. Blanks were also run at the same time using ashed filter papers. Calcium and magnesium were determined by atomic absorption spectrophotometry (Perkin-Elmer Model 303 Atomic Absorption Spectrophotometer). Sodium and potassium were measured by flame photometry (Instrumentation Laboratory Inc., Flame Photometry 343) and inorganic phosphate using the Phosphorus Rapid Stat kit (Pierce, Illinois).
107
JANETHOMPSON 0. 5r
(cl
. .
.
.
0.4l
. i:
l
i .2
*
B
l.
c.0
.
. .
0 I.3 -
.
. . 0. 2>
.
fd) Oi PO -
l
*
* .
. E 0
m
cl! 55 -
*
i
3 t z 2 0.4 io -
l l
.
. Oi!5l
.
0 IOI
240
I
I
400
320
0
Follicle wet weight, mg
,
8
240
320
Follicle wet weight, mg
i 240
I
320
1Magneelum, 400
Follicle wet weight, mg
Fig. I. Changes in the calcium (a), magnesium (b), sodium (c) and potassium (d) content of developing follicles of S. quoyii. The data are combined in Fig. 1 (e) for comparison.
Mineral uptake by lizard embryo Estimationof the age of embryos In captured adult females follicles developed
approx.
synchronously and, during the breeding season, at any one time, pregnant females carried embryos at approximately the same stage of gestation. Therefore the age of embryos was estimated by taking Day 1 as the day on which I first found females which had ovulated, assuming that fertilization took place at ovulation.
RESULTS
Changes in the composition of calcium, magnesium, sodium and potassium in developing follicles are shown in Fig. 1. There was a significant increase in amount of all ions. The relative increase in calcium was greater than for the other measured ions. The whole egg Changes in inorganic ion content of the whole egg are shown in Fig. 2. Total calcium content increased, the most rapid rate of increase being in the last third of the gestation period. Sodium, and potassium also increased but there was no significant change in the amount of magnesium. Total inorganic phosphorus in the. ash of eight eggs collected soon after ovulation was 4.07 + 0.18 mg (X + SEM) compared with 3.87 f 0.26 mg in 8 whole eggs containing embryos at term. The difference is not statistically significant (ti* = 0.64, P > 0.25). 7he embryo and yolk sac To determine whether ions taken up by the whole egg were incorporated into the embryo, changes in the calcium, magnesium, sodium and potassium content of the embryo and yolk sac were measured at different stages of gestation (Fig. 3). The amounts of calcium, sodium and potassium in embryos near term were greater than the amounts of these ions initially present in the yolk. The gains in all three ions were equivalent to the total gains measured in the whole egg. As expected, there was no gain in the amount of magnesium in the embryo. There was a steady decline in the amount of all ions in the yolk, except sodium, where there was a peak at about the time of midgestation. This coincides with the rise in water content of the yolk (Thompson, 1977b, 1982).
DISCUSSION
There is a 21% increase in the ash content of the eggs of S. quoyii during development (Thompson, 1977a). While there may be transplacental flow of inorganic ions in both direction there is thus a net gain in the inorganic ion content of the egg. The only other report of an increase in ash content in a viviparous reptile is for Pseudechis porphyriacus, where the ash content increased by 54% (Shine, 1977). The present study shows that the major part of the increase in total ash content in S. quoyii eggs during development can be attributed to uptake of calcium with a small net gain in sodium and potassium. Furthermore, it has been shown that all of these additional ions are incorporated into the embryo.
109
There has been some discussion in the literature regarding the sources of calcium for developing reptile embryos. Packard et at. (1977), concluded that all of the calcium (and probably magnesium) required by the reptile embryo is present in the egg at the time of ovulation. This conclusion is supported by the findings of a number of authors (Cunnin~am er al., 1939; Bustard & Greenham, 1968; Jenkins & Simkiss, 1968; Bustard et al., 1969; Jenkins, 1975). Packard et al. (1977) suggested that in reptiles there are two fundamentally different means for provision of calcium to the embryo. Embryonic crocodilians and chelonians recover calcium from the egg shell and the yolk does not contain all the calcium necessary for skeletal development (Bustard et al., 1969; Jenkins, 1975). The yolk of chelonians is apparently rich in magnesium, however (Bustard, et al., 1969). In contrast, embryos of snakes and lizards, including some geckos which produce calcareous egg shells, probably obtain all the necessary calcium and magnesium from rich stores present in the yolk alone (Jenkins 8z Simkiss, 1968). In the only study, to my knowledge, of a viviparous species, Jenkins & Simkiss (1968) found no increase in the total quantities of either calcium, phosphorus or magnesium during development of embryos of the snake Vipera berus. They concluded that the yolk was rich enough in ions necessary for skeletal formation and there was no need to postulate a role of the placenta in supplying additional ions. Their findings differ from the results with S. quoyii where there is a definite intake of calcium. It is interesting therefore to compare the concentration of calcium in the yolk of S. quoyii with that in other reptiles. Jenkins & Simkiss (1968) claimed that in comparison with turtles, the calcium content of the yolk of squamates is relatively high. The calcium content of the yolk of a number of species is compared in Table 1. The calcium content of the yolk in S. quoyii is less than reported values for other squamates but higher than that of turtles and chickens. With a reduced amount of calcium in the yolk it may therefore be necessary for additional calcium to be transferred to the embryo via the placenta. This may also be true for sodium and potassium although there are no measurements of these ions in the yolk of any reptile for comparison. Alternatively or in addition, uptake of sodium and potassium may be necessary to enable active transport of water which is taken up during development. The pattern of sodium uptake corresponds to that of water uptake (Thompson, 1977h 1982). Calcium taken up by the embryo may not be used immediately for bone formation. It is known that reptile embryos store calcium as CaCO, in the endolymphatic sacs of the inner ear (Simkiss, 1967; Jenkins & Simkiss, 1968). Obvious white deposits in these sacs were observed in S. quoyii embryos. Thus calcium may be stored and used later for bone formation.
~ck~ow~e~~e~e~rs-I thank Drs Gordon Grigg, Richard Shine and Associate Professor John Simons for their interest and advice. The research was supported by a Commonwealth Postgraduate Research Award. I thank Mrs Wendy Guy for her typing.
JANETHOMPSON
112
Table 1. Calcium content of the yolk of eggs of different species
Species
Calcium mg ‘A of wet weight
Fowl Turtles: Dermorhelys coricacea Thalassoche~ys corticata Pseudem~ls scipta
Snakes : Viper0 berm Thamnophis sauritus
Reference
104
Urist & Schjeide (1961)
94 72 212
Simkiss (1967) Needham (1931) Urist & Schjeide (1961)
959 1400
Simkiss (1967) Dessaur & Fox (1959)
Lizards: Anguis fragihs Lacerta vivipara Hemidactylus frenatus Hemidactylus turcicus S. quoyii
REFERENCES
BUSTARDH. R. & GREENHAM P. (1968) Physical and chemical factors affecting hatchjng in the green sea turtle, Chelonia mydas (L.). Ecology 49, 269-276. BUSTARDH. R., SIMKISSL. & JENKINS N. K. (1969) Some analyses of artificially incubated eggs and hatchlings of green and loggerhead sea turtles. J. Zool., Lond. 158, 311-31s.
CLARKH. & SIXEN B. F. (1956) Nitrogenous excretion by embryos of the viviparous snake Thamnophis s. sirtalis (L.). J. exp. Biol. 33, 384393. CONAWAYC. H. & FLEMINGW. R. (1960) Placental transmission of Na22 and Ir3’ in Natrix. Copeia 196453-55. CUNNINGHAMB., WOODWARDM. W. and PRIDGEN J. (1939) Further studies on incubation of turtle (Mafaclefflys centrata Lat.) eggs. Am. Nat. 73, 28.5-288. DESSAURH. C. & Fox W. (1959) Changes in ovarian foihde composition with plasma levels of snakes during estrus. Am. J. Physics. 197, 360-366. HOFFMANL. H. (1970) Placentation in the Garter Snake, ~hamnophis sirtalis. J. Morph. 131, 57-88.
JENKINSN. K. (1975) Chemical composition of the eggs of the crocodile (Crocodyius novaeguinea). Comp. Biochem. Physiol. 51A, 891-895. JENKINSN. K. & SIMKI~.Y K. (1968) The calcium and.phosphate metabolism of reproducing reptiles with particular reference to the adder (Vipera berus). Comp. Biochem. Physiol. 26, 865-876.
713 916
1500 1100 425
Jenkins Jenkins Jenkins Jenkins
81 Simkiss & Simkiss & Simkiss & Simkiss
(1968) (1968) (1968) (1968)
NEEDHAMJ. (1931) Chemical Embryology. Cambridge University Press, London. PACKARDG. C., TRACY R. C. & ROTH J. J. (1977) The physiologic~ ecology of reptilian eggs and embryos and the evolution of viviparity within the Class Reptilia. Biol. Rev. 52, 71-105. SHINER. (1977) Reproduction in Australian elapid snakes. II. Female reproductive cycles. Aust. J. Zool. 25, 655-666. S1~~rs.s K. (1967) Calcium in reproductive physiology. Chapman & Hall, London. THOMPWNJ. (1977a) Embryo-maternal relationships in a viviparous skink, Sphenomorphus quoyii (Lacertilia: Scincidae) In Reproduction and Evolution. (Edited by CALABY J. H. & TYNDALE-BISCOE C. H.) pp. 279-280. Australian Academy of Science. THOMPSONJ. (1977b) Embryo-maternal relationships in a viviparous lizard, Sphenom~rphus quoyii (Dumerii and Bibronf. Ph.D. Thesis, University of Sydney. 158 pp. THOMPSON J. (1982) A study of the sources of nutrients for embryonic development in a viviparous lizard, Sphenomorphus quoyii. Camp. Biochem Physioi. (In press). URIST M. R. & SCHJEIDEA. 0. (1961) The partition of calcium and protein in the blood of oviparous vertebrates during estrus. J. gen. Physiol. 44, 743-756. WEEKESH. C. (1927) Placentation and other phenomena in the scincid lizard Lygosoma (Him&a) quoyii. Proc. Linn. Sot. N.S.W! 52, 499-554.