Meeting Abstract

29.4  Monday, Jan. 5  Endocrine mechanisms mediating temperature-induced reproductive behavior in garter snakes (Thamnophis sirtalis). LUTTERSCHMIDT, D.I.*; MASON, R.T.; Georgia State University, Atlanta; Oregon State University, Corvallis lutterschmidt@gsu.edu

In many hibernating ectotherms, photoperiod cues likely have little or no influence on the initiation of spring reproductive behavior. Rather, temperature may be the most important environmental cue for synchronizing seasonal rhythms. We investigated the mechanisms by which temperature induces seasonal reproductive behavior in red-sided garter snakes (Thamnophis sirtalis parietalis). Specifically, we addressed whether elevated environmental temperatures during winter dormancy influence (1) patterns of sex steroid hormones; (2) diel melatonin and corticosterone rhythms; and (3) the expression of courtship behavior following emergence. Elevated hibernation temperatures (i.e., 10C versus 5C) significantly decreased androgen concentrations of male snakes during winter dormancy, presumably via increased metabolic clearance. In contrast, estradiol concentrations of female snakes increased significantly during winter dormancy and were not affected by hibernation temperature. Elevated hibernation temperatures also significantly increased melatonin and decreased corticosterone concentrations of snakes. The cold temperature-induced differences in melatonin rhythms between the 5C and 10C hibernation temperature groups persisted even after both groups were again acclimated to 10C, indicating that cold temperature exposure has a lasting influence on melatonin rhythms. Following winter dormancy, we observed robust courtship behavior in all treatment groups. However, males maintained at 10C during winter dormancy exhibited delayed onset of courtship behavior. Our results suggest that environmental temperatures induce reproductive behavior, in part, via changes in melatonin and/or corticosterone rhythms in this seasonally breeding reptile.