Abstract

Desert vertebrates exhibit remarkable physiological mechanisms for surviving in extreme environments. In addition, species with short breeding seasons often exhibit behavioral and physiological adaptations to increase breeding success within a narrow window. Couch’s spadefoot (Scaphiopus couchii) is a burrowing frog found throughout the Desert Southwest. Spadefoots live in extreme environments, especially for amphibians, and exhibit a well-known explosive breeding system associated with brief periods of intense monsoon rainfall. Outside of the breeding season spadefoots aestivate underground for prolonged periods. The hormone pattern associated with the breeding system of this frog has been studied, however, the effect of long-term aestivation on immunocompetence in S. couchii has not been examined. We captured 53 spadefoots from west Texas and induced aestivation in the laboratory. We tested immunocompetence using a bacterial killing assay after 4 week, 6 week, and 8 week aestivation treatments. Preliminary results suggest that longer aestivation reduces immunocompetence, with bacteria only killing 7.7% of plasma within the 4 week treatment group, bacteria killing 43.9% of plasma within the 6 week treatment group, and bacteria killing 60.3% of plasma within the 8 week treatment group. This suggests that spadefoots incur a physiological cost for their capacity for prolonged aestivation and may be more susceptible to pathogens or parasites during dry periods.

Authors

• Alexandria-Jade Martinez Roberts, Sul Ross State University

• Sean Graham, Sul Ross State University