A taxonomic reassessment of Cirrodrilus japonicus (Pierantoni, 1912) (Annelida, Clitellata, Branchiobdellida).

Cirrodrilus japonicus (Pierantoni, 1912) has not been identified since it was originally described from specimens removed from preserved Japanese crayfish that had been deposited in the Natural History Museum in Hamburg, Germany. A morphological comparison of the published description and recently discovered syntypes of C. japonicus from the Hamburg Museum with syntypes and newly collected material of Cirrodrilus ezoensis (Yamaguchi, 1934), supported the view that preservation artifacts in C. japonicus caused Prof. Yamaguchi to believe his well-preserved specimens were member of a separate species. Therefore, C. ezoensis becomes a junior synonym of C. japonicus.

Taxonomical study of Japanese emAulodrilus/em Bretscher (Annelida, Clitellata, Tubificinae) with descriptions of two new species.

Seven species of the genus Aulodrilus (Annelida, Clitellata, Tubificinae) are studied, based on new material from Japan. Aulodrilus dentosus sp. nov. is characterized as having tubular atrium, forked or bifid distal ends of dorsal crotchets, but no genital chaetae, and A. aestivus sp. nov. is characterized as having crescent-shaped atrium, median male bursa, and bifid chaetae in the dorsal bundles. Five other congeners are redescribed: A. limnobius Bretscher, A. pluriseta (Piguet), A. pigueti Kowalewski, A. japonicus Yamaguchi, and A. americanus Brinkhurst Cook. Comparison of taxonomic characters among the 14 species recognized in the genus to date shows that three species differ from other congeners in several features: A. paucichaeta Brinkhurst Barbour, A. adetus (du Bois-Reymond Marcus), and A. apeniatus Cui Wang. They are provisionally maintained in the genus.

Multi-locus phylogenetic analysis of the genus Limnodrilus (Annelida: Clitellata: Naididae).

Limnodrilus species are annelid worms distributed worldwide in various freshwater sediments. The systematics of Limnodrilus has chiefly been based on morphology, but the genus has not been subject to any closer phylogenetic studies over the past two decades. To reconstruct the evolutionary history of Limnodrilus, and to assess the monophyly of this genus and its systematic position within the subfamily Tubificinae (Annelida: Clitellata: Naididae), 45 Limnodrilus specimens, representing 19 species, and 35 other naidid species (representing 24 genera) were sampled. The data consisted of sequences of three mitochondrial genes (COI, 12S and 16S rDNA) and four nuclear markers (18S and 28S rDNA, Histone 3, and ITS). The phylogeny was estimated, using Maximum Likelihood and Bayesian analyses of concatenated data of seven DNA loci, as well as a multi-locus coalescent-based approach. All analyses strongly suggest that Limnodrilus is monophyletic, but only if the morphospecies L. rubripenis is removed from it. Limnodrilus rubripenis and (at least) Baltidrilus, Lophochaeta and some species attributed to Varichaetadrilus comprise the sister group to the clade Limnodrilus sensu stricto, and the latter is further divided into three well-supported groups. One of them contains morphospecies characterized by short cuticular penis sheaths and enlarged chaetae in anterior segments (L. udekemianus, L. silvani and L. grandisetosus). The second is a small group of species with moderately long penis sheaths, i.e., L. sulphurensis and L. profundicola. The third, and largest group, includes not only the multitude of cryptic species in the L. hoffmeisteri complex, but also other, morphologically distinct, species nested within this complex. All studied species in this large group have long penis sheaths, which are exceptionally long in L. claparedianus, L. maumeensis, and a form morphologically intermediate between L. claparedianus and L. cervix. The identification and classification of these groups provide a framework for directed sampling in further phylogenetic studies, and for revisionary work on the L. hoffmeisteri complex and other unresolved Limnodrilus species.

Redescriptions of Spirosperma apapillatus and Embolocephalus nikolskyi (Annelida, Clitellata, Tubificinae) from Japan, with reference to distribution of papillate tubificines in Japanese freshwaters.

Based on new specimens, two freshwater papillate tubificines, Spirosperma apapillatus (Lastockin in Lastockin and Sokolskaja, 1953) and Embolocephalus nikolskyi (Lastockin in Lastockin and Sokolskaja, 1953) are redescribed, and geographic distributions are shown for these two species and E. yamaguchii (Brinkhurst, 1971) in the Japanese archipelago. A geographic cline from northern Hokkaido to northern Honshu is suggested by the distribution of simple-pointed ventral chaetae in Japanese E. nikoslkyi. That species is replaced by E. yamaguchii in the south, beginning in northern Honshu. Tubifex (Peloscolex) nomurai Yamatoto and Okada, 1940 , which was described from deep profundal bottoms in Lake Tazawa, Japan, may be ascribed to E. nikolskyi, or may be closely related; the definitive status is not settled.

Yamaguchia toyensis n. sp., n. gen. (Annelida, Clitellata, Lumbriculidae) from profundal Lake habitat in Japan.

Yamaguchia toyensis n. sp., n. gen. is described from an oligotrophic caldera lake, Lake Toya, Hokkaido, Japan. Although the taxonomic affinities are unknown, the genus differs from all other Lumbriculidae in having the combination of testes and atria in X, a single, prosoporous male funnel per atrium, and spermathecae in XI. Unlike other Japanese lakes that have thus far been surveyed, Lake Toya supports abundant populations of lumbriculids in the profundal benthos.

A new species of the subterranean genus Krenedrilus dumnicka (Oligochaeta, Tubificidae) from the deep bottom of an oligotrophic caldera lake in Japan.

A new tubificid oligochaete, Krenedrilus towadensis, is described from deep bottoms of the oligotrophic caldera Lake Towada in northern Japan. It resembles K. realis Martínez-Ansemil and Collado, 1996, in the combination of somatic setae, but it is different from all other congeners by the lack of spermathecal setae and epidermal papillae in X, in the structures of penial and supernumerary setae, and in the location of spermathecal pores. The definition of Krenedrilus is revised.