Effects of Training and Testosterone on Muscle-Fiber Types and Locomotor Performance in Male Six-Lined Racerunners (\u3cem\u3eAspidoscelis sexlineata\u3c/em\u3e)

Testosterone (T) is thought to affect a variety of traits important for fitness, including coloration, the size of sexual ornaments, aggression, and locomotor performance. Here, we investigated the effects of experimentally elevated T and locomotor training on muscle physiology and running performance in a nonterritorial male lizard species (Aspidoscelis sexlineata). Additionally, several morphological attributes were quantified to examine other characters that are likely affected by T and/or a training regimen. Neither training alone nor training with T supplementation resulted in increased locomotor performance. Instead, we found that T and training resulted in a decrease in each of three locomotor performance variables as well as in hematocrit, ventral coloration, and testis size. Strikingly, neither the size nor the fiber composition of the iliofibularis or gastrocnemius muscles was different among the two treatments or a group of untrained control animals. Hence, the relationships among T, training, and associated characters are not clear. Our results offer important insights for those hoping to conduct laboratory manipulations on nonmodel organisms and highlight the challenges of studying both training effects and the effects of steroid hormones on locomotor performance

A systematic review on integration mechanisms in human and animal health surveillance systems with a view to addressing global health security threats

Lymphatic filariasis and onchocerciasis are neglected tropical diseases (NTDs) targeted for elimination by mass (antifilarial) drug administration. These drugs are predominantly active against the microfilarial progeny of adult worms. New drugs or combinations are needed to improve patient therapy and to enhance the effectiveness of interventions in persistent hotspots of transmission. Several therapies and regimens are currently in (pre-)clinical testing. Clinical trial simulators (CTSs) project patient outcomes to inform the design of clinical trials but have not been widely applied to NTDs, where their resource-saving payoffs could be highly beneficial. We demonstrate the utility of CTSs using our individual-based onchocerciasis transmission model (EPIONCHO-IBM) that projects trial outcomes of a hypothetical macrofilaricidal drug. We identify key design decisions that influence the power of clinical trials, including participant eligibility criteria and post-treatment follow-up times for measuring infection indicators. We discuss how CTSs help to inform target product profiles

The Ontogeny of Carapace Morphology in Gopher Tortoises (\u3cem\u3eGopherus polyphemus\u3c/em\u3e)

Juvenile gopher tortoises (Gopherus polyphemus) have a domed carapace whereas adults have a noticeably flattened carapace. Given their domed appearance and small size, we hypothesized that the domed carapace of juveniles decreases the righting response time in the event that the individual is flipped onto its back (e.g. by a predator). This study quantified the ontogeny of carapace morphology in Gopherus polyphemus. Seventy five juvenile to adult gopher tortoises were photographed in lateral and dorsal views. Using morphometric software (tpsDig), 26 landmarks were digitized from each photograph. This approach allowed us to quantify the important region(s) of shape change over a broad range of sizes including hatchlings, juveniles, and adult tortoises. Furthermore, we linked changes in morphology with behavior by quantifying the righting response across this same sample. Large adult gopher tortoises can not right themselves and can die if left on their back. Given the initial observation of the domed carapace of juveniles, we hypothesized that juveniles would be able to right themselves faster than adult tortoises with their dorsoventrally flattened carapaces. To test this, we flipped tortoises onto their backs and measured the time it took them to right themselves. Trials were conducted in an arena containing loose, very sandy soil that is identical to the sandhill environs that gopher tortoises inhabit. Regardless of size or shape, only 6.7% of tortoises were able to right themselves. We conclude that the change in carapace morphology is not related to the righting response. Instead, carapace shape may relate to allometric patterns of growth, and/or the pronounced increase in burrowing activity individuals exhibit as they mature

Seasonal Variation in Testosterone and Performance in Non-Territorial Male Lizards

The ability to perform key behaviors, particularly those associated with reproduction, has been linked to reproductive success. However, it remains unclear as to which underlying mechanisms govern variation in the performance capacities of these behaviors. Due to its ability to mediate physiological and morphological changes, the steroid hormone testosterone has been hypothesized to influence performance. This hypothesis, however, has not been tested in a broad range of taxa or mating systems. In this study, seasonal patterns of bite force and locomotor performance were quantified concurrently with circulating testosterone levels in males of a non-territorial polygynous lizard species (Aspidoscelis sexlineata). Bite force and one measure of locomotor performance were significantly greater in the breeding season than in the post-breeding season, and this seasonal variation in performance was correlated with seasonal changes in testosterone levels. These results suggest that the performance capacities of behaviors important for acquiring mating opportunities in this species are maximized during the breeding season by elevated testosterone levels

Biology and Conservation of North American Tortoises

Tortoises, those unmistakable turtles, evolved from a lineage that split off from the familiar pond turtles roughly 100 million years ago. Over time, these plant-eating land turtles spread around the world, growing to an enormous size (depending on the species) and living so long that they have become the stuff of legends. By most accounts, they are indeed the longest-lived of the turtles, with good records suggesting individuals may live as long as 180 years (anecdotal records suggest that some reach ages of 200 years or more). Providing the first comprehensive treatment of North America’s tortoises, Biology and Conservation of North American Tortoises brings together leading experts to give an overview of tortoise morphology, taxonomy, systematics, paleontology, physiology, ecology, behavior, reproduction, diet, growth, health, and conservation. The contributors carefully combine their own expertise and observations with results from studies conducted by hundreds of other researchers. The result is a book that belongs in the library of every herpetologist

Effects of Testosterone on Bite Force and Locomotor Performance in the Six-Lined Racerunner

Numerous studies have examined the effects of testosterone on behavior in territorial lizards, but few have explored the role of testosterone (T) in non-territorial species. Here, we experimentally manipulated T levels in Aspdidoscelis sexlineatus, a common non-territorial lizard. During the breeding season, males exhibit mate guarding, and will follow a female for several days after copulation. Male-to-male interactions during the breeding season involve chasing and occasionally escalate into fights with biting. Therefore, high bite force and high endurance capacity should be advantageous to retain exclusive access to females and ensure paternity. In territorial lizards, T levels peak with the breeding season and several studies have cited T as a possible mediator of the seasonal increases in performance (e.g. bite force and locomotor performance). Fluctuating T levels have been observed in A. sexlineatus; however, the role that T plays in the performance of A. sexlineatus or other mate guarding species remains unknown. For this study, male racerunners were captured and blood samples were drawn immediately to quantify T levels. Lizards were then returned to the lab where locomotor performance (endurance), bite force, and morphological data were collected. Following performance trials, lizards received silastic T implants. Lizards were housed in the lab for four weeks where locomotor endurance and bite force performance were measured biweekly. Additionally, a blood sample was collected every two weeks to monitor T levels. This research will quantify the morphological and physiological factors affecting performance in A. sexlineatus and provide valuable data concerning how T affects alternative mating systems

Seasonal Variation in Bite Force and Endurance in the Six-Lined Racerunner (\u3cem\u3eAspidoscelis sexlineata\u3c/em\u3e)

This talk was given during the Southeast Regional Meeting of the Society for Integrative and Comparative Biology