Meeting Abstract
The cost-benefit paradigm between reproduction and survival is a common biological theme. Despite much research, the endocrine mechanisms that allow organisms to mediate trade-offs between reproducing and surviving are poorly understood. Leptin has been implicated in mediating these trade-offs. In mammals, leptin is synthesized by adipocytes in proportion to cell size, and thus reliably indicates energy status. However, studies in non-mammalian vertebrates suggest the role of leptin is not well conserved. To better understand if and how leptin mediates reproductive trade-offs across taxa, we identified a leptin-like protein in red-sided garter snakes (Thamnophis sirtalis parietalis). We utilized a combination of enzyme immunoassay and Western blot to determine the presence of leptin in plasma, liver, and adipose (i.e., fat body) tissues. We identified a leptin-like protein in the plasma of both male and female snakes. Western blot results indicate a higher concentration of leptin in plasma than in fat bodies or liver, consistent with the hypothesis of constitutively-released leptin. Next, we asked if exogenous leptin treatment influences reproductive behavior of snakes. Leptin did not significantly alter male courtship intensity. In contrast, the proportion of leptin-injected females that copulated was higher than that of control-treated individuals. There were no differences in latency to copulate or the duration of copulation between groups. In addition, we observed no differences in the morphometrics of males that succeeded in copulating with leptin- vs. control-treated females. These results indicate that leptin is involved in reproductive “decision making” in female garter snakes, and also suggest that the role of leptin in mediating reproductive trade-offs may be conserved.
