The Role of Testosterone and Training on Locomotor Performance in a Non-Territorial Lizard

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The effects of testosterone (T) on territorial lizards have been studied extensively; however, the effects of T on non-territorial lizards have not. In territorial lizards, T has been suggested as a possible mediator of seasonal increases in whole-animal performance capacities (i.e. sprint speed and bite force), which are important factors in maintaining territories and winning male-male competitions. Previous work in our lab has shown that in Aspidoscelis sexlineata, a common non-territorial lizard, bite force, locomotor performance (measured as the max. time until exhaustion), and T are each greatest during the breeding season; thereby suggesting that T also mediates seasonal increases in performance for this species. Furthermore, T implants have been shown to successfully elevate circulating T levels in A. sexlineata. However, the T implants failed to increase whole-animal performance capacities, and hence suggest a training effect. The current study will test the effects of training on locomotor performance capacities and morphology (i.e. locomotor muscle size & composition). Thirty adult male A. sexlineata were assigned to one of three treatment groups: T implant + training, empty implant + training, and empty implant without training. Training consisted of 3 performance measures: treadmill endurance, burst speed, and maximal exertion. At the end of the study, changes in muscle size, muscle fiber size, or fiber-type composition were assessed for multiple hindlimb muscles using histochemical analyses to determine the influence of treatment group (T, training regime). This research will further isolate the role of T and training on the morphological factors affecting seasonal locomotor performance in non-territorial species.


Society for Integrative and Comparative Biology Annual Meeting (SICB)


Seattle, WA