A New Phreodrilid Species (Annelida: Clitellata: Phreodrilidae) from Lake Biwa, Japan

Abstract

A new species of Phreodrilidae is described from Lake Biwa, Japan, using classical morphology and a 658 bp long fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene as a potential "DNA barcode". Astacopsidrilus ryuteki sp. nov. is unusual in possessing dorsal bundles each represented by only a single seta, instead of the usual hair and support setae. Among other phreodrilids, this feature has been reported only in Nesodrilus isochaeta Pinder and Brinkhurst, 1997 and Insulodrilus bifidus Pinder and Brinkhurst, 1997, both described from Australia. The new species possesses paired spermathecal setae and peculiar voluminous, pendant penes. This is the first record of the family in Japan, a circumstance that contradicts the assumed Gondwanan origin of the Phreodrilidae. Because any hypothesis of a former zoogeographical connection between Japan (or other parts of Asia) and Australia is unsupported by any other biogeographical data, it is probable that A. ryuteki was introduced to Japan from the Southern Hemisphere. Conversely, the tubificid Embolocephalus yamaguchii (Brinkhurst, 1971) appears to have been introduced into Australia from Japan.