Differences in size, pigmentation, and fluctuating asymmetry in stressed and nonstressed northern leopard frogs (Rana pipiens)

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Abstract
We compared a range of anatomical features of northern leopard frogs (Rana pipiens Schreber) collected from areas where deformity rates were low (-2% in nonstressed regions) and high (-40% in the stressed region) to determine if one or more of these characters might be useful in detecting developmental stress. Deformed individuals from the stressed region were significantly lighter than normal frogs both from the same region and from nonstressed regions. Body length, head width, femur length, and forelimb length were also significantly shorter in deformed and normal individuals from the stressed region than in individuals from nonstressed regions. Despite being smaller, deformed individuals had significantly larger pigment spots. Fluctuating asymmetry in femur length, femur spot area, femur spot number, and tibio-fibula length was significantly greater in deformed frogs than in normal frogs from the stressed population and the nonstressed group. Of these characters, however, only femur spot number provided a data set suitable for fluctuating asymmetry analysis (R - L values have a normal distribution, no directional asymmetry, no size-dependent asymmetry). There were no significant differences found among the three groups for fluctuating asymmetry in forelimb length, eyespot area, lateral spot number, and lateral spot area.