Meeting Abstract

27.5  Friday, Jan. 4  Do androgens mediate seasonal changes in sexual signal size and bite-force performance in green anoles (Anolis carolinensis)? HENNINGSEN, JP*; HUSAK, JF; IRSCHICK, DJ; University of Massachusetts Amherst; University of Massachusetts Amherst and Virginia Tech; University of Massachusetts Amherst justinh@bio.umass.edu

Sexually dimorphic structures are common in nature and often play an important role in the reproductive biology of many species. Green anoles (Anolis carolinensis) have an extendable throat fan, or dewlap, used in intra- and intersexual encounters. Recent work has shown that dewlap size and bite force change seasonally within an individual. To test whether this seasonal plasticity is mediated by testosterone (T), we castrated green anoles and administrated exogenous T during the breeding season. We found that dewlap size tended to decrease more in a control group treated with a sham surgery and a blank implant than in a group castrated and administered exogenous T. Additionally, the group treated with T increased the size of the dewlap dorso-ventrally, while the control group showed no change. When measured antero-posteriorly, the T group showed no change in dewlap size, while the control group showed a significant decrease. Green anoles that were given exogenous T displayed a significant negative relationship between initial dewlap size and percent change in dewlap size. The same relationship existed for bite force. However, the relationship was absent in intact animals. We also measured the cartilaginous element most likely to affect dewlap size, ceratobranchial II. This work provides strong evidence that T mediates seasonal changes in dewlap size in green anoles.