Meeting Abstract

P1.132  Saturday, Jan. 4 15:30  Reproductive axis activation following photostimulation in a wild female songbird GUARDADO, D*; PERFITO, N; HAU, M; BENTLEY, G.E.; Univ. of California, Berkeley ; Univ. of California, Berkeley ; Max-Planck Inst. of Ornithology, Germany; Univ. of California, Berkeley daisy.guard@gmail.com

The ability to respond to environmental signals is critical for the timing of reproduction. To this end, the seasonal change in photoperiod is one of the most reliable environmental cues available. Both male and female songbirds increase circulating gonadotropins (luteinizing hormone, LH, and follicle stimulating hormone, FSH) in response to photostimulation. However, the sexes exhibit distinctly different patterns of gonadal maturation. Currently, we do not understand the neural mechanisms responsible for the sex differences described above, as females have not been studied in this regard. We can begin to investigate this topic by utilizing the “first-day release model,” which predicts rapid changes in several photoperiodically controlled genes and activation of the reproductive axis following exposure to a single long day. This model was developed using male Japanese quail. Recently, our lab has shown that this model is also relevant to males of a wild species, the great tit (Parus major). Similar key genes are involved in the photoperiodic response of the two species. However, it is not known if females of any species exhibit similar changes in gene expression in response to long days. To determine this, we exposed wild female great tits to a long day stimulus and measured changes in key genes during the first 46 hours of photostimulation (Dio2, Dio3, FSH-β and GnRH). Preliminary results suggest that patterns of gene activation in female great tits are similar to those observed in males, suggesting that sex differences in patterns of gonadal development might be achieved by a mechanism other than that which underlies the basic photoperiodic response.