Aliens vs. Amphibians: New Data on Amphibians’ Eсtoparasitic and Endoparasitic Leeches (Annelida: Hirudinea) of Vietnam and China

Leeches are common parasites of amphibians and can affect them through blood loss, pathogen transmission, and predation, yet leech–amphibian interactions remain poorly documented in Indochina. This study provides the first documented cases of leech parasitism on amphibians from Vietnam and adjacent southwestern China. Amphibian-associated leeches appear to be widespread across the studied region, occurring across a broad range of habitats and elevations. Ectoparasitic associations were recorded for three hirudinean families (Haemadipsidae, Glossiphoniidae, and Salifidae) across northern and southern Vietnam, where leeches use at least 12 species (seven genera, five families, two orders) of amphibians as hosts. Most notably, we documented true endoparasitism by praobdellid leeches in the abdominal cavity of anurans, comprising 22 cases across five host species of the family Ranidae and two host species of the family Bufonidae from five localities in northern Vietnam and southwestern China. To our knowledge, such a case of endoparasitism has not been previously reported from the Asian region or for praobdellid leeches. Our findings substantially expand current knowledge of leech–amphibian interactions in Indochina, highlight a previously unrecognized life-history strategy in Praobdellidae, and provide a baseline for assessing potential impacts of leech parasitism on amphibian health and conservation in the region.