Hatching Plasticity Under Complex Conditions: Responses of Newt Embryos to Chemical and Mechanical Stimuli from Egg and Larval Predators

Abstract

Environmentally cued hatching plasticity is a common attribute of the eggs of oviparous organisms that has been especially well studied in amphibians. Nevertheless, this process has been largely overlooked in species with complex natural histories. We exposed embryos of the rough-skinned newt (Taricha granulosa) to chemical and mechanical stimuli from multiple potential threats, including caddisfly larvae, a major predator on the egg stage of newts. Newt embryos did not exhibit hatching plasticity toward chemical cues from any treatment but, contrary to prediction, did delay hatching in response to mechanical stimuli from an egg predator. Observations of predation by caddisfly larvae on recently hatched newt embryos indicate that caddisflies may prey on multiple life history stages of T. granulosa. The results of this study indicate that hatching plasticity may be a complicated phenomenon in some taxa and that additional factors, such as toxicity of eggs or larvae and maternal behavior, may play an important role in the evolution of this phenomenon.