Pleurodeles waltl Newt Larvae Diet Regarding Available Prey: Choice or Mere Coincidence?

Abstract

Vernal pools are preferred breeding habitats for numerous amphibian species. The analysis of prey composition during the amphibian larval stages is necessary to understand diet composition and food choice in aquatic communities. We studied the diet of larvae of Pleurodeles waltl when exogenous feeding begins and throughout the flooding period in an episodic Mediterranean pond. The stomach contents were analyzed and the diet was compared to the availability of prey in the pond. The diet analysis revealed an ample diversity of prey, the most abundant being cyclopoid and calanoid copepods and podocopid ostracods. Changes in the composition of the diet corresponded principally to the variations in the availability of different prey as a consequence of the succession of the zooplankton community throughout the flooding period. However, certain taxa such as large anostracans, small anomopods, and turbellarias were not consumed although they were available and abundant. In contrast, prey scarcely represented in the pond such as coleopteran, dipteran, and hemipteran larvae were efficiently captured, suggesting their accessibility to newt larvae. The proportion of prey found in stomachs with respect to their abundance in the pond increased with larval size, coinciding with a reduction in number and bio-volume of available prey. The results suggest that newt larvae are opportunistic feeders and that breeding success of newts may be highly dependent on early egg-laying to match the abundant food supply found at early flooding stages of vernal pools.