Meeting Abstract

20.4  Jan. 5  Opportunism at work: regulation of the reproductive axis in wild populations of zebra finches. PERFITO, N.*; UBUKA, T.; ZANN, R.A.; HAU, M.; BENTLEY, G.E.; Univ. of California, Berkeley; Univ. of California, Berkeley; LaTrobe Univ., Melbourne, Australia; Princeton Univ., New Jersey; Univ. of California, Berkeley nperfito@berkeley.edu

Zebra finches Taeniopygia guttata are thought to maintain their reproductive systems in a near-ready state in order to respond quickly to environmental conditions favorable for breeding. This strategy differs markedly from that used by obligately photoperiodic species in which changing photoperiod is used as a cue to modulate gonadotropin-releasing hormone (GnRH) release and thus reproductive activation on a seasonal basis. The discovery of a novel RFamide neuropeptide, gonadotropin inhibitory hormone (GnIH), and its subsequent characterization in mammals, provides an exciting and completely new avenue for investigating reproductive systems. GnIH acts in opposition to GnRH in birds, inhibiting gonadotropin synthesis and release by the anterior pituitary gland in vitro and in vivo. The goal of the present study was to characterize immunoreactivity of GnIH and GnRH in zebra finches captured in the field under two very different environmental and breeding conditions: one from a seasonal population during springtime breeding conditions and another from a population in a more unpredictable habitat during non-breeding conditions and while experiencing drought. We expected from previous findings that ir-GnRH cell number and size would be similar between populations, but that ir-GnIH cells would be larger and more numerous in the non-breeding drought population. Differential regulation of these two important reproductive hormones might help to explain the physiological underpinnings of opportunism.