Survival and growth of the caddisfly Limnephilus flavastellus after predation on toxic eggs of the Rough-skinned Newt (Taricha granulosa)

Abstract

The Rough-skinned Newt ( Taricha granulosa (Skilton, 1849)) possesses a powerful neurotoxin, tetrodotoxin, in the skin that is secondarily deposited in the ova. Although assumed to serve an antipredator function in the eggs, empirical evidence of the toxin’s role in preventing egg predation is lacking. In this study, we characterized the aquatic macroinvertebrate community at a location sympatric with extremely toxic newts and estimated the abundance of caddisflies. We tested aquatic macroinvertebrates sympatric with toxic newts for their capacity to consume the toxic eggs, and examined the propensity of egg predation and its effect on growth of the only known predator of newt eggs, caddisfly larvae. Limnephilid caddisfly larvae were the only invertebrate observed to consume substantial quantities of toxic newt eggs. Survival and growth of the caddisfly Limnephilus flavastellus Banks, 1918 continued when larvae consumed toxic eggs and did not differ from L. flavastellus that also had access to an alternative food source (detritus). Limnephilus flavastellus that had access to eggs + detritus consumed a similar number of eggs compared with those provided with eggs only. These results, combined with the abundance of caddisflies, suggest that caddisflies are important predators of eggs of T. granulosa.