BEECHER, N.A.*; DEMAS, G.E.; Indiana University; Indiana University: Frog declines: exploring connections between climate change, immunity and disease.

For the past 16 years, marked declines have been recorded for 40% of the frog and toad species in the Monteverde Cloud Forest Preserve (MCFP), Costa Rica. With 15 years of population monitoring and 30 years of climate data published, and in nearby areas of Central America the chytrid fungus and other pathogens documented, climate change and disease serve as two strong hypotheses to explain these declines. To explore possible connections between climate change, immunity and disease susceptibility, our research examines how climate-induced changes in pond water levels may influence immune responses. We examined immune development and function (antibody production, skin graft rejection and antimicrobial peptide production) in meadow treefrogs (Hyla pseudopuma), a metamorphically-plastic and declining species in the MCFP, when tadpoles developed under various water regimens. During the wet seasons of 2000-2004, laboratory experiments were conducted by subjecting tadpoles to a constant (8cm) or sharp decline in water level (2cm). Field studies took place in man-made and natural forest ponds that experienced different rainfall and pond water retention patterns. Our studies suggest that tadpoles and froglets that developed in shallow or highly variable water levels had blunted immune responses. Preliminary analyses suggest that tadpoles produced lower levels of antibodies, and 1-month-old froglets were less able to reject foreign tissue. These data support the hypothesis that climate-induced changes in pond water can influence immune development and function. Collectively, these results may have important implications concerning climate change effects on amphibian populations, as well as the possible role of immunosuppression and increased disease susceptibility in species declines.