First repor t of the interac tion between the toad Melanophryniscus nigricans and the leech Helobdella cordobensis in the Tandilia Mountains

Melanophryniscus nigricans is an endangered endemic anuran species restricted to the TandiliaMountains in Argentina. We report for the first time the interaction between this toad speciesand the leech Helobdella cordobensis. We observed the interaction in a temporary pond at the“Sierra del Tigre” Natural Reserve during a breeding event of M. nigricans on February 7th, 2024.A leech was found attached to the belly of a toad and removed manually with no evidence ofinjury in the amphibian, suggesting a case of phoresis instead of parasitism. This report is alsothe first documented phoretic interaction between H. cordobensis and anurans from Argentina.