Semernodrilus confusus ( Semernoy, 2004 ) Timm, 2020

Timm, Tarmo, 2020, A literature revision of Pararhyacodrilus Snimščikova, 1986, with the erection of a new genus, Semernodrilus gen. nov. (Oligochaeta, Tubificidae, Rhyacodrilinae), Zootaxa 4786 (3), pp. 431-436 : 435

Semernodrilus confusus ( Semernoy, 2004) , comb. nov.

Pararhyacodrilus confusus: Semernoy 2004, pp. 168–170 , Fig. 85.

Remarks. The new genus is accomodated in Rhyacodrilinae due to the typical structure of the male duct, with a short and prostate-covered atrium, and due to the penial chaetae, as depicted by Semernoy (2004, Fig. 85). This as- sigment can only be disputed because of the described absence of coelomocytes in the type species. Coelomocytes are typical of the Rhyacodrilinae ; however, they can be scarce and difficult to observe in several other rhyacodriline species (my own observation). As an opposite example, “rhyacodriline” coelomocytes occur abundantly in Phallodrilus granifer Erséus, 1990 (= Pectinodrilus granifer ), a member of the subfamily Phallodrilinae , commonly devoid of them ( Erséus 1990). The prolonged esophagus, up to segment X, is very rare among tubificids (a specific character in Aulodrilus japonicus Yamaguchi, 1953 , after Hrabĕ 1981). The forward shift of the genital system by two segments seems to be common in the architomic tubificids after the regeneration of the anterior end ( Hrabĕ 1981, p. 119). However, a shift by only one (as in Semernodrilus ) or two segments has been found to be also an individual variation in some tubificids, e.g., in the Baikalian rhyacodriline Svetlovia majusculata Čekanovskaja, 1975 ( Semernoy 2004, p. 177). The connection of the spermathecae with the digestive tract, apparently facilitating utilization of unused sperm ( Westheide 1999), is common in many enchytraeid genera and has certainly evolved independantly in the lumbriculid genus Rhynchelmis and in the rhyacodriline genus Pararhyacodrilus . A convergent origin of this structure also in Semernodrilus is plausible. Presence or lack of hair chaetae (different in Pararhyacodrilus and Semernodrilus ) is not a generic character in many rhyacodriline and tubificine oligochaetes. Thus no single character listed above but a combination of them justifies the formal treatment of Semernodrilus gen. nov. as a separate, monotypic genus of the subfamily Rhyacodrilinae . Its actual affinities remain unknown without mo- lecular biological studies.