CONICET | Buscador de Institutos y Recursos Humanos

In avian species living at high altitudes and latitudes, reproductive events are largely controlled by the photoperiod, changes in the latter being perceived mainly through encephalic photoreceptors located in the hypothalamus. It is known that during long daylight periods (reproductive periods), the information transmitted by brain photoreceptors triggers the metabolism of thyroid hormones that regulate GnRH secretion, inducing secretion of pituitary gonadotropins. As a result, gonads develop and grow and the production of gonadal sex hormones, testosterone and estradiol increases (classic gonadal cycle). During short daylight periods (non-reproductive periods) on the other hand, the gonads are retracted and plasmatic gonadal steroid levels are low. By means of this mechanism, birds are able to synchronize their physiology and reproductive behaviors with the annual cycle. However, it appears that not all avian species comply with this reproductive pattern. For example, the Eared Dove (Zenaida auriculata), a South American opportunistic breeder columbiform, has been reported to be successfully reproductive throughout the year, making it an interesting avian system for studying the endocrine basis of avian reproduction. In view of a clear lack of seasonal variability in testicular weight and size (the classic gonadal regression/recrudescence cycle) in the male Eared Dove, we examined whether their reproductive success could be the result of being in a continuous state of reproductive preparedness. Our results show that despite the absence of a marked gonadal cycle in terms of gonadal volume, plasma testosterone levels in males were minimal during autumn-winter, reaching maximum values during spring-summer. This indicates that male gonad functionality is seasonal and is synchronized with the photoperiod, demonstrating an exception to the classic model of reproduction in birds.