Eastern Newt (Notophthalmus viridescens) larvae alter morphological but not chemical defenses in response to predator cues

Prey traits are often modified in response to exposure to predators, a phenomenon known as predator-induced phenotypic plasticity. Morphological plasticity in response to predator cues is well documented in amphibians; however, predator-induced chemical defenses have received relatively little attention. The Eastern Newt (Notophthalmus viridescens (Rafinesque, 1820)), which possesses tetrodotoxin-a toxin for chemical defense, is most vulnerable to predation during its larval stage. We assessed whether exposing Eastern Newt larvae to predator scent cues (from dragonfly larvae) would elicit change in their morphological and chemical defenses. Newt larvae exposed to scent cues of predatory dragonfly larvae exhibited significantly greater tail depths, which should increase survival of attempted predation by allowing them to swim faster, but did not differ in mass, snout-vent length, or tail length. Toxin concentrations in newt larvae were not significantly affected by exposure to these predator cues. Larval toxicity may be derived maternally or environmentally and is inflexible, or induced toxicity may only be detectable later in development. Predator-induced phenotypic plasticity, especially of chemical defenses, warrants greater attention, as potentially important outcomes of species interactions remain unclear.