Variation of the Syrinx of the Fowl

THYROXINE SECRETION

ally from about 12.8°C. to 23.9°C. After 7 days the TSR determination was repeated. At this time the mean TSR of the group was 0.53 ixg./100g. b.w., a reduction of 41.8,%. A second group of 23 hens maintained for 2 years at room temperature showed a mean TSR of 052 (Ag./100g. b.w. It was concluded that fowls placed in a cold environment showed increasing TSR for a number of months, whereas the change to a warm environment results in a very rapid decline in TSR.

33

RATE REFERENCES

Hendrich, C. E., and C. W. Turner, 1963. Time relations in the alteration of thyroid gland function in fowls. Poultry Sci. 42: 1190-119S. Pipes, G. W., B. N. Premachandra and C. W. Turner, 19S8. Measurement of the thyroid hormone secretion rate of individual fowls. Poultry Sci. 37: 36-41. Stahl, P., and C. W. Turner, 1961. Seasonal variation in thyroxine secretion rates in two strains of New Hampshire chickens. Poultry Sci. 40: 239-242. Stahl, P., G. W. Pipes and C. W. Turner, 1961. Time required for low temperature to influence thyroxine secretion rate in fowls. Poultry Sci. 40: 646-650.

Variation of the Syrinx of the Fowl G. VICTOR M O R E J O H N

Department of Biological Science, San Jose State College, San Jose, California (Received for publication April 5, 1965)

T

HE purpose of this study was to determine if significant differences exist between breeds of domestic fowl and supposed ancestral species of jungle fowl with reference to the syrinx. The importance of the syrinx in determining degree of relationship in certain avian groups has been recognized for many years. The organ has been found to be highly variable in some species (Bronn, 1891), and sexual dimorphism has been shown to be marked in most song birds and in ducks and owls (Broman, 1942; Lewis and Domm, 1948; Miller, 1934; Biellier and Turner, 1950). The anatomy of the syrinx of the red junglefowl (Gallus gallus) was studied and compared with the domestic fowl as early as 1813 by Temminck; Garrod (1879) did likewise in his extensive study of the syrinx in the Gallinae. The comparative anatomist, Wunderlich (1884), not only compared the syrinx of several avian species but also noticed differences between the syrinx of the

domestic fowl and that of G. gallus. Myers (1917) has made the most extensive study of the anatomy of the syrinx of the adult domestic fowl and the developing embryo. The more recent work of Appel (1929) indicates that certain variations of the structure of the syrinx can be shown to exist in certain breeds of fowl and not in others. Appel states that certain features of the syrinx, for example in the Brown or White Leghorn, differ from those found in Buff Orpingtons, Plymouth Rocks, and Silver and Golden Sebright bantams, although he did not mention which parts of the syrinx in particular differed. MATERIALS AND METHODS

Live specimens of Gallus gallus (8 cocks, 4 hens), Gallus sonnerati (2 cocks, 2 hens), and the interspecific hybrid G. gallus—G. sonnerati (3 cocks) were sacrificed for studies on the syrinx. Two frozen specimens of G. varius cocks were also used. The syrinx of representatives of

34

G. V. MOREJOHN

both sexes of the domestic fowl were studied as well. Ten White Leghorns (5 cocks, S hens); eight Cornish (6 cocks, 2 hens); nine New Hampshires (5 cocks, 4 hens); and one Barred Rock (hen) were examined. The Leghorns were used as representatives of the "Mediterranean" breeds of fowl; and the New Hampshires and Barred Rock as "American" breeds. The Cornish represented a modified "Asiatic" breed. The syringes were removed and placed in 70% alcohol. Once fixed in this medium they were immersed in 0.1% methylene blue solution in distilled water to stain the cartilaginous elements. Upon completion of staining (IS minutes), the syringes were placed in 50% alcohol for one hour to destain the non-skeletal tissue.

The syringes were then placed in 70% alcohol and made ready for study by removal of excess tissue and membranes covering the cartilaginous elements. In analysis of the material primary emphasis was placed upon demonstrating the differences which consistently separate the three wild species of Gallics from each other. Secondarily, an attempt was made to show the range of variability in the syringial structure that exists in some domestic breeds of fowl. The syrinx of this genus, in contrast to the complex syringes of song birds, is quite simple in structure. The largest skeletal part of the syrinx is the pessulus which is situated at the junction of the bronchi in a dorso-ventral position in a vertical plane across the long axis

dorsal pessulus transverse pessulus

syringial bars

bronchial half-rings

tracheal rings

ventral pessulus FIG. 1 Diagrammatic drawings of the osseous and cartilaginous elements of the syrinx.

3S

SYRINX OF THE FOWL

dorsal pessulus

Callus

varius syringial bars sternotrachealis

Gal/us gol/us

external tympanic membrane

bronchial half-rings

Gallus

tracheal rings

sonnerali

ventral pessulus FIG. 2. Lateral views of the syrinx of three species of Gallus demonstrating the differences between the species.

of the trachea (Fig. 1). The first bronchial half-ring of each bronchus is attached dorsally and ventrally to the pessulus. The external tympanic membrane extends from each half-ring and from the attachment on the ventral and dorsal pessulus, anteriorly to the tracheal rings. Approximately half of this membrane is supported by thin elastic, cartalaginous syringial bars which are weakly fused to the lateral edges of the ventral pessulus. The internal tympanic membrane is a continuation anteriorly of

the median membranous wall of the bronchi (bronchidesmus of Myers, 1917) to the posterior edge of the vertical pessulus. The syrinx of the three species studied all have this basic structure. RESULTS

The differences in the species are found in: (1) the shape of the first bronchial half-ring; and (2) the number of syringial bars supporting the external tympanic membrane. No females of G. varius were avail-

5(3

G. V. MOREJOHN

dorsal

^J/

ventral

FIG. 3. The syrinx of Gallus varius.

able for study at this time and consequently no sexual comparisons could be made. The differences between the sexes of the species G. gallus, G. sonnerati and the domestic fowl have been only in total size, length of tympanum, ossification (only as an indicator of age), and some slight differences in proportions. It is assumed, for the present comparison, that the same

differences would obtain between the sexes of G. varius. Some of the syringial differences in the species are seen in Figure 2. The first bronchial half-rings which attach to the dorsal and ventral parts of the pessulus are distinctly different in varius (Fig. 3). From the ventral aspect the "hammer-head" shape typical of gallus

dorsal

ventral FIG. 4. The syrinx of Gallus gallus.

37

SYRINX OF THE FOWL

dorsal

ventral Fie. 5. The syrinx of Gallus sonnerati.

(Fig. 4) and sonnerati (Fig. S) is absent in varius. The second, third, and fourth bronchial half-rings are much shorter in length and do not extend around to the medial bronchial wall as they do in the other two species. The number of syringial tympanic bars seems to be variable in gallus and domestic breeds, but sonnerati has the least (1-2) and gallus and varius are similar in having four to five pairs. The caudal slips of the sternotrachealis muscles were found to have extremely variable points of insertion on the tracheal cartilages. The dorsal and ventral slips also had branches which varied from one to five. Little structural variation was found in the Leghorns. The cartilaginous syringial bars vary from 4-5 as in gallus, and in all other respects the syrinx is identical with that of gallus. Among the Cornish employed, three (2 cocks, 1 hen) were excellent representatives of the Dark Cornish breed, and exhibited similar syringial characteristics (Fig. 6). Five other WhiteLaced Red Cornish (4 cocks, 1 hen) did not have the odd syringial characteristics of the Dark Cornish. The typical hammer-

head shape of the first bronchial half-ring from ventral aspect was lacking in the Dark Cornish, and also the close juxtaposition of this structure with the second bronchial half-ring, as in G. gallus, G. sonnerati, and the other domestic forms, was lacking. The White-Laced Red Cornish differed from all the others in the highly variable number of syringial bars (1-6). The syrinx of one of these hens was indistinguishable from the syrinx of sonnerati (with the exception of size) in having only one prominent syringial bar on each side. The New Hampshires and Barred Rock were essentially identical and resembled the Leghorns closely but were more massive in structure, similar to Cornish. The only variability was in the number of syringial bars which ranged from five to seven. DISCUSSION

The study of the syrinx demonstrated clearly that the organ in G. varius as compared to the other species is different (Fig. 2). It would be difficult indeed, to attempt to correlate form with function of this structure. Doubtless, the many parts of the syrinx contribute their share to the produc-

3.\

G. V. MOREJOHN

FIG. 6. The syrinx of the dark Cornish breed of domestic fowl. Note the comparative lack of the •'hammer head" shape of the first bronchial half-ring where it fuses with the ventral pessulus. Also note the lack of juxtaposition of the second bronchial half-ring with the first (compare with Figures .3,4, and S).

tion of sounds distinctive of the species. The main item of interest in this regard is that the crowing sounds made by G. gallus, G. sonnerati and G. lajayettei (the fourth species yet unexamined) are similar, that is, they can be recognized as the crowing of a fowl. Each may be represented as follows: gallus, ka ka kaya kaaa; sonnerati, ka ka kayak; lajayettei (after Beebe, 1926) craw croy; whereas the voice of varius is an explosive chaw-aw-awk. In this respect, only an association of the main differences in the syrinx can be correlated with the crowing type. The "call of content" of sonnerati uttered by both hens and cocks is not similar to that of the familiar gallns.The sound may be likened to a low rasping "meow" of a cat. Marler et al. (1962) studied crowing patterns in strains of domestic fowl by comparing sonogram recordings. They found little variation in strains of White Leghorns, but a greater variation pattern

was found in crossbred fowls some having Cornish ancestry. In Java Fi hybrid i>«n'2«-domestic fowl cocks are produced by staking out domestic hens which then mate with G. varius cocks. They are prized for their long monosyllabic call and many crowing contests are held in native villages. Oana (1954), in describing the origin of the Japanese longtailed fowls, mentioned some of the ancestors from China as having been prized for their long crowing ability. He believes, furthermore, that the Chinese long-crowing fowls are related to the Sumatra. This breed of domestic fowl is related to the Malay, Aseel and Cornish breeds of fowl. SUMMARY

The syringes of three species of junglefowl and representative domestic breeds were dissected and studied. The three species of junglefowl were readily distinguishable from one another on the basis of

SYRINX OF THE FOWL

peculiar characteristics of the first bronchial half rings of the bronchi and the number of syringial bars which occur in the external tympanic membrane. One species (G. varius) was more distinct than the other two. The domestic breeds studied showed resemblances to the three species studied, particularly to G. gallus and G. sonnerati. The Cornish breed, however, had more characteristics of G. varius than the other breeds. ACKNOWLEDGMENTS

The Poultry Science Department of the University of California at Davis donated most of the domestic fowl used. The research work was accomplished at the Department of Zoology at the same institution. Dr. K. E. Stager of the Los Angeles County Museum kindly donated a frozen specimen of Gallus varius for dissection. REFERENCES Appel, F. W., 1929. Sex dimorphism in the syrinx of the fowl. J. Morph. Physiol. 47: 497-518. Beebe, W., 1926. Pheasants: Their Lives and Homes. Vols. / and 11. Doubleday, Doran and Company, Inc., New York. Biellier, H. V., and C. W. Turner, 1950. Sexual

39

dimorphism in the syrinx of the Pekin duck. Poultry Sci. 29 : 527-529. Broman, I., 1942. Uber die Embryonalentwicklung der Enten-Syrinx. Anat. Anz. 93: 241-251. Bronn, H. G., 1891. Klasen und Ordnungen des Thierreichs, VI Vogel, von Gadow und Selenka. Garrod, A. H. O., 1879. On some anatomical characters which bear upon some major divisions of the Passerine birds. Proc. Zool. Soc. London, 506. Lewis, L. B., and L. V. Domm, 1948. A sexual transformation of the osseus bulla in duck embryos following administration of estrogen. Physiol. Zool. 21: 65-69. Marler, P., M. Kreith and E. Willis, 1962. An analysis of testosterone-induced crowing in young domestic cockerels. Animal Behavior, 10: 4854. Miller, A. H., 1934. The vocal apparatus of some North American owls. The Condor, 36: 204213. Myers, J. A., 1917. Studies on the syrinx of the domestic fowl. J. Morph. 29: 165-216. Oana, J., 1954. The origin of the Japanese longtailed fowls. Tenth World's Poultry Congress: 9-12. Temminck, 1813. Histoire naturelle des pigeons et gallinaceas. Vols. I-II, Amsterdam (1813 and 1815). Wunderlich, L., 1886. Beitrage zur vergleichenden Anatomie und Entwicklungsgeschicte des unteren Kehlkopfes der Vogel. Nova Acta d. Kais. Leopold-Carol, (als inaug.-Diss., 1884).

NEWS AND NOTES RULES OF THE WORLD'S POULTRY SCIENCE ASSOCIATION— U.S.A. BRANCH

gresses, and by cooperating with the Poultry Science Association in securing travel grants for the participants in the Congress program. (b) To increase the membership of the World's Poultry Science Association in the United States of 1. Name. The name of the Branch shall be the United States of America Branch of the World's America. (c) To cooperate with trade associations in Poultry Science Association. (For brevity in correspondence, printing etc. United States of America promoting better understanding between the poultry industry in this country and those in other may be abbreviated to U.S.A.) parts of the world. 2. Objects. The objects of the Branch are: (d) To cooperate with the Poultry Science As(a) To provide for the participation of the United States of America in World's Poultry Con- sociation in promoting participation of poultry gresses by maintaining a standing Participation scientists in all international efforts related to poulCommittee with rotating membership, by exerting try science and industry. (e) To promote the exchange of knowledge in appropriate influence on Government agencies to secure the accreditation of an official delegation, all fields of the poultry industry in accordance by promoting industry participation in the Con- with article II of the Constitution of W.P.S.A. (Continued, on page 57)