Description of a new leech species from North America, Helobdella austinensis n. sp. (Hirudinea: Glossiphoniidae), with observations on its feeding behaviour

摘要

Freshwater leeches of the genus Helobdella Blanchard 1896 are small, proboscis-bearing glossiphoniids of the family Rhynchobdellidae that have been found worldwide. Over the past three decades, annelid developmental biologists have used several Helobdella species as model organisms. Here we describe a variable taxon, that has been studied extensively, and was formerly labelled as Helobdella sp. "robusta" (Austin), as a new species, Helobdella austinensis n. sp. Diagnostic features of this polymorphicspecies, which has a body length of 13 to 17 mm and a yellow-brown colour, include a characteristic pattern of dark longitudinal stripes with black, conical papillae on the dorsal side of the body, irregularly arranged white pigment spots, and the lackof a nuchal scute. The type locality is Shoal Creek, Austin, Texas, USA. Based on the sequence of part of the mitochondrial gene cytochrome c oxidase subunit I, H. austinensis n. sp. is a defined taxon that differs genetically from other, morphologicallysimilar Helobdella species by 11 to 17%. Under laboratory conditions, hungry leeches suck body fluids from living freshwater snails, dead (frozen-thawed) Chironomus larvae, and crushed (wounded) crustaceans. Aquatic oligochaetes (Tubifex worms) and living insect larvae are ignored. This specific prey selection is a characteristic feature of H. austinensis, a taxon that differs, based on morphological features, from its relatives of the South American triserialis species complex.