Are toxic effects of alien species affected by their prey? Evaluation by bioassay with captive-bred toad embryos and a vulnerable predator

Toads of the Family Bufonidae possess neurotoxins (bufadienolides) which are generally considered to be synthesized de novo. Thus, invasive toad species pose a threat native predators via toxic effects. However, influence diet on toxicity is poorly understood. We evaluated effect embryos Bufo japonicus formosus in Japan, using tadpoles (Rana pirica) as bioassay. Specifically, we compared spawned by captive toads reared entirely non-toxic prey versus wild toads. Embryos captive-reared and were comparable terms effects: all that consumed embryo died, irrespective origin embryos. Embryo appears parental (likely maternal) provisioning. Our study indicates adult B. j. produce toxins bufadienolides) amounts sufficient for fatal predator whether contains toxins. effects R. pirica, possibly other sensitive species, likely widespread occur regardless variation biota invaded areas Japan.