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A comparative study of the annual cycles in sexual and thyroid function in male Peking ducks (Anas platyrhynchos) and teal (Anas crecca)

1978; Elsevier BV; Volume: 36; Issue: 2 Linguagem: Inglês

10.1016/0016-6480(78)90023-0

1095-6840

Monique Jallageas, Alain Tamisier, I Assenmacher,

Animal Behavior and Reproduction

The annual variations in plasma levels of LH, testosterone, and thyroxine and in testis weight were measured in two large groups of teal (128) and Peking ducks (104) living outdoors. Both species displayed a biphasic sexual cycle, with (1) a main reproductive phase in spring, associated in the teal with sexual displays, (2) a decrease in all sexual parameters from June through July, and (3) a transitory sexual recovery in August–September. The plasma thyroxine cycle showed an annual maximum in June–July, at the time of the postnuptial molt. Teal underwent an additional annual peak of plasma thyroxine in December, i.e., during the coldest season but also around the time of the winter molt. The possibility of testis-thyroid interactions is discussed. Further experimental studies on teal and ducks kept in bioclimatic chambers have shown the stimulatory effect of long days on gonadotrophin secretion in teal as in ducks, and the inhibitory effect of cold on sexual function.