A revision of the Tubificidae and Lycodrilidae (Annelida, Oligochaeta) known from Lake Baikal

Abstract

Twenty-five species in 10 genera are reported from Lake Baikal, though the number of each is uncertain because of remaining taxonomic problems. Twenty of the species are endemic, the remaining five being the previously reported Spirosperma (as Peloscolex) velutinus and Rhyacodrilus coccineus, and the newly reported Tubifex superiorensis. T. kessleri and T. acapillatus. The last two consist of a complex of subspecies, some of which may be endemic; R. coccineus inaequalis is also reported as an endemic subspecies in the literature. Five of the genera are endemic: Baikalodrilus (formerly part of Peloscolex) with three or four species. Lycodrilides (two species). Lycodrilus (one species), and the monotypic abyssal Svetlovia and Rhyacodrilides. Other presently described abyssal forms (Tubifex taediosus. T. minutes, Peloscolex malevici) are of doubtful generic attribution and could increase the list of endemic genera. These species were not available for this study, nor were Rhyacodrilus korotneffi and R. multispinus from the north of the lake, and Lycodrilus phreodriloides, a species listed as incertae sedis in Lycodrilus until it is redeseribed. The Tubifex species described here support the contention that the genus is polyphyletic, and two groups (Tubifex sensu stricto and sensu lato) are recognized. The description of the type species of Isochaetides may precipitate further revision of that taxon also. The Family Lycodrilidae consists of two tubificine tubificid genera plus a lumbriculid, and is, therefore, dissolved. Most common holarctic and palaearctic genera are absent. The names Tubifex excavatus (Hr.) and Lycodrilides grubei (Mich.) are new combinations.