PARENT SESSION
Oral Session 14: Reptiles and Amphibians I: Salamanders and Newts.
Presiding: K McCoy
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room D 136.
Seasonal variation in infection and immunity in eastern red-spotted newts.
Raffel, Thomas*,1, Kiesecker, Joseph1, Hudson, Peter1, 1 Pennsylvania State University, University Park, PA, USA
ABSTRACT- Understanding what factors influence the distribution and abundance of infectious disease in amphibians may be important to understanding widespread reports of declining amphibian populations. The objective of this study was to measure seasonal variation in the abundance of pathogens and parasites of red-spotted newts (Notophthalmus viridescens), in order to test whether newts show predicted seasonal patterns in immune system parameters and disease prevalence. Laboratory experiments have shown a decrease in several immune system parameters at low temperatures compared to high temperatures. On the basis of these experiments, previous workers have predicted that 1. amphibians living in temperate climates should have suppressed immune function during winter and 2. rates of infection should be highest during the early spring, after water temperatures become warm enough to allow proliferation of bacterial and fungal pathogens but before the amphibian immune system has a chance to recover. To examine these predictions, we have conducted a seasonal survey of red-spotted newts in five ponds. Results showed a strong effect of temperature on several immune system parameters, verifying the first prediction, but data on seasonal infection prevalence for multiple parasites, including Ichthyophonus, suggest that the highest infection rates occurred in late summer rather than early spring. Other factors, such as seasonal fluctuations in the density of newts and the abundance of intermediate hosts for parasites, may help explain this pattern.
Key words: amphibian, immunity, newt, parasite