Meeting Abstract
The synchronization of physiology and behavior with favorable environmental conditions is tightly linked to an animal’s fitness. This synchronization depends on an organism’s ability to transduce environmental cues, such as photoperiod and temperature, into neuroendocrine signals that regulate physiological and behavioral processes. These neuroendocrine signals are critical to understanding the seasonality of vertebrate reproduction. Relative to photoperiod, however, there is comparatively little research on the potential role of temperature, despite the fact that many vertebrates (especially ectotherms) use temperature as a cue for timing seasonal mating. We hypothesized that temperature-activated reproduction is mediated by changes in thyrotropin synthesis within the pituitary pars tuberalis. We tested this hypothesis in red-sided garter snakes (Thamnophis sirtalis) using simulated winter dormancy, immunohistochemistry, and behavior assays. Field-collected snakes were hibernated at 4°C or 12°C in complete darkness and euthanized at 0, 4, 8, or 16 weeks in hibernation. Brains were collected and processed for thyrotropin (a.k.a. thyroid stimulating hormone, TSH) immunohistochemistry; we quantified the number of immunoreactive cells within a subregion of the anterior pituitary gland that is akin to the pars tuberalis. Our results suggest that TSH immunoreactivity in this pars tuberalis-like region changes in response to hibernation at 4°C for at least 4 weeks. Moreover, the observed changes in TSH mirror the effects of low-temperature dormancy on male courtship behavior. We suggest that TSH within the pars tuberalis can be modulated by environmental temperature, and these temperature-induced changes may in turn facilitate the effects of temperature on seasonal reproduction.
