Connecting aquatic and terrestrial environments: bioaccumulation of ivermectin in amphibians throughout metamorphosis

Ivermectin is a drug used for parasite control in cattle that is excreted through the feces, remaining available for its bioaccumulation in non-target aquatic organisms. Our objective was to evaluate the bioaccumulation of this drug in larval stages of Physalaemus albonotatus (Pa) and P. santafecinus (Ps) and its potential transference throughout metamorphosis to terrestrial metamorphs. In a 24-day laboratory experiment, tadpoles (Gosner stage 30) of both species were placed individually in plastic containers with dung that either included or omitted ivermectin (1000 ng/g). Tadpoles were removed every 2 or 3 days, as well as those that reached Gosner stage 45/46. Ivermectin concentration was determined by HPLC, measured in eviscerated tadpoles. Both species bioaccumulated ivermectin at different development stages, including final stages of metamorphosis. Ivermectin concentration was higher in P. albonotatus than in P. santafecinus, with differences observed between stages and over exposure time. Surprisingly, despite being congeneric species occupying a similar ecological niche, these taxa showed different bioaccumulation factors for ivermectin. Our results provide novel evidence that ivermectin can be biologically transferred across larval stages and from aquatic to terrestrial ecosystems through metamorphosis. We also highlight the importance of further assessing bioaccumulation mechanisms and potential impacts on food webs in closely related species.