Acid Tolerance in Connecticut Wood Frogs (Rana sylvatica)

Abstract

Acid tolerance limits were measured in wood frog (R. sylvatica) embryos and larvae from a population located in New London, Connecticut. Among embryos, relative hatching success was high and not significantly different in solutions with pH 7.2-7.6, pH 6.0, pH 5.0 and pH 4.0 pH 3.75 relative hatching success dropped to 50% and less than 1% of embryos survived at pH 3.5 or below. At pH 4.0 the number of developmental abnormalities among surviving embryos increased significantly and at pH 3.75 35% of surviving embryos appeared abnormal. Larvae were more acid tolerant than embryos and this tolerance appeared to increase as the larvae developed. Measurements of acidity in the natural breeding habitat indicated that considerable temporal and spatial variation may occur within a single pond, but the levels of acidity measured did not exceed the species'' tolerance limits.