Decimodrilus, Dózsa-Farkas & Nagy & Felföldi & Hong, 2019

Dózsa-Farkas, Klára, Nagy, Hajnalka, Felföldi, Tamás & Hong, Yong, 2019, Decimodrilus, a new enchytraeid genus from Korea (Annelida, Clitellata, Enchytraeidae), Zootaxa 4661 (2), pp. 385-399 : 386

Genus Decimodrilus gen. n.

Type species: Decimodrilus diverticulatus sp. n.

Included species:

Decimodrilus diverticulatus sp. n.

Decimodrilus globulatus sp. n.

Etymology. Named after the characteristic tenth segment (decimus = tenth, Latin) in which the largest part of the intestinal diverticulum is located.

Genus diagnosis. Maximum of 4–5 (6) chaetae per bundle. Chaetae straight or slightly bent in a bundle arranged in asymmetric fan of unequal size, those towards dorsal and ventral midlines of body gradually smaller. Head pore longitudinal slit on prostomium dorsally, often inconspicuous. In the ventral nerve cord perikarya continuous, also in the region of the septa. Brain truncated posteriorly, slightly incised anteriorly. Oesophageal appendages absent. Intestinal diverticula present or the gut widened abruptly with thickened epithelium in IX–X. Dorsal blood vessel origin in clitellar region, anterior bifurcation in segment I. Anteseptale of nephridia consisting of funnel only, efferent duct arises antero-ventrally or mid-ventrally. Coelomocytes one type, mucocytes. Male reproductive system simple, vas deferens long, not widened. Male pores in usual position in XII, with well-developed glandular bulbs. Spermathecae united proximally and connect jointly with the oesophagus dorsally.

The new genus is similar in some traits to genera Bryodrilus , Enchytronia , Globulidrilus, Guaranidrilus , Henlea and Oconnorella , but for differences from these similar genera, see Table 1 . Characteristic features of the new genus are the intestinal diverticula in IX–X and the longitudinal slit of the head pore. Henlea differs from the new genus chiefly by the preclitellar origin of the dorsal vessel, and the presence of oesophageal appendages (vs. absent in the new genus). In Bryodrilus and Oconnorella intestinal diverticula are absent (vs. present in the new genus), but most species of these genera have oesophageal appendages in VI or IV–VI, or VII (vs. absent); they are also absent in some species of Oconnorella . In Guaranidrilus the maximum number of chaetae is only 2 (vs. 4–6), the brain is incised posteriorly (vs. truncate), the spermathecae are free (vs. attached to oesophagus), and the head pore is on the prostomium (vs. at 0/I). Globulidrilus has sigmoid chaetae (vs. straight) and intestinal diverticula are absent.