SICB 2019: The Effect of Testosterone on Male Aggressive Behavior in A. sagrei and A. cristatellus

Gianni Solis presents her work entitled “Effects of arginine Vasotocin and mesotocin on aggression in male Caribbean anoles.”

Male aggression in Anolis lizards is governed by the circulating sex hormone, testosterone. Two species of anoles, the brown anole (Anolis sagre) and the Caribbean anole (A. cristatellus), both exhibit high aggression. However, A. sagrei has low concentrations of testosterone in comparison to A. cristatellus. This suggests that there may be other underlying mechanisms governing male aggression rather than just testosterone.

Regulation of aggressive behaviors in male Anolis lizards was the focus of Gianni Solis’ poster presentation at the 2019 SICB conference. Solis is an undergraduate sophomore at University of St. Thomas under Dr. Jerry Husak, although one would think she is an established graduate student based on her knowledge and enthusiasm for this project. She predicted that there would be a difference in aggressive behaviors exhibited by A. sagrei and A. cristatellus and these behaviors would be influenced by Arginine Vasotocin (AVT) and Mesotocin (MT).

Solis examined aggressive behaviors towards a mirror in A. sagrei, a low-testosterone species, and A. cristatellus, a high-testosterone species. IP injections of non-steroid hormones AVT and MT were given along with Phosphate Buffered Saline (PBS) as a control. After a 15-minute acclimation period, aggressive behaviors were documented in 20-minute lengths. Latency, total number of bouts, average and total duration, and combination of displays were recorded. Aggression scores were calculated utilizing a PCA and a one-way ANOVA identified statistical significance.

While her results were non-significant, potentially due to small sample size, statistically close values suggest that there may have been an influence of AVT and MT on aggressive behaviors. MT-injected A. sagrei tended to be less aggressive than other treatments and MT-injected A. cristatellus tended to be more aggressive than other treatments. Other mechanisms by which these behavioral differences occur between both species, such as potential estrogenic influences, may also be the target for future studies. Anolis male aggressive responses and underlying processes remain in question, however, we are looking forward to hopefully seeing Solis again with more questions at SICB 2020.