Phagodrilus gen.nov. (Lumbriculidae): systematics and biology of a predaceous oligochaete from western North America

Abstract

The genus Phagodrilus (Lumbriculidae) is erected for Phagodrilus macnabi sp.nov., a predaceous worm with a paryngeo-esophageal region resembling that of Agriodrilus, a monotypic genus from Lake Baikal, often cited as a potential progenitor of the leeches. The pharynx or gizzard of Phagodrilus has the opposite dorsoventral orientation of its triangular section to that of Agriodrilus (apex dorsad in Phagodrilus, ventrad in Agriodrilus). While the latter appears closely related to Lamprodrilus in terms of its reproductive system, Phagodrilus resembles the Stylodrilus–Hrabea complex. These characteristics clearly indicate separate origins of the predatory habit and convergence of these two taxa, which suggests reexamination of the relationship between them and the leeches and branchiobdellids.