Cernosvitoviella atrata (Bretscher, 1903)

(Figure 12)

Material examined. 11 specimens (two were deposited in the National Institute of Biological Resources, Korea; NIBRIV0000837801, in 70 % ethanol) .

Our observations agree with the emended description of Dózsa-Farkas et al. (2017), but the specimens from Korea are slightly smaller: 2–4 mm long, 140–170 μm wide at VIII and 170–200 μm at XII (vs. 3–5 mm and 170–250 μm wide at clitellum), segments 19–24. Chaetae sigmoid with nodulus, up to 6–7 per bundle, 32–40 μm long. Brain incised posteriorly (Fig. 12A). Nephridial anteseptale with funnel only, postseptale with conspicuous canal, efferent duct terminal (Fig. 12D). Two pairs of primary and two pairs of secondary pharyngeal glands (Fig. 12F). Coelomocytes 14–20 μm long (Figs 12C, D), variable, mostly oval, without or with refractile granules, brown in transmitted light. Dorsal vessel origin in XII–XIII, anterior bifurcation peristomial (Fig. 12B). Blood light pink. Seminal vesicle absent. Sperm funnels conical, 55–80 μm long, vas deferens long and 15–20 μm wide proximally and gradually taper to a 8–11 μm wide duct distally (Fig. 12E). Male opening surrounded by glands. Spermatozoa 30–50 μm, heads 15–25 μm long. Spermatheca (Fig. 12F) confined to V, ampullae elongate, about as long as or slightly shorter than the length of the ectal ducts, sperm arranged lengthwise. Although Chalupský (1992) observed two forms of this species (Form I and II), which differ mainly in the shape of spermatheca, such differences were not observed by Dózsa-Farkas et al. (2017) and in this study. Nevertheless, as it was raised by Schmelz et al. (2015) based on specimens collected from Honduras, it is possible that worms currently regarded as C. atrata are members of a species complex.

Distribution and habitat in Korea. Muljangori-oreum Wetland, Bonggae-dong, Jeju-si, Jeju-do, N 33°24’29.04”, E 126°36’23.41”, 812 m asl; Mt. Gyebangsan, Nodong-ri, Yongpyeong-myeon, Pyeongchang-gun, Gangwon-do, Q. mongolica forest, N 37°42’27.92”, E 128°29’02.34”, 848 m asl; Mt. Chiaksan, Hakgok-ri, Sochomyeon, Wonju-si, Gangwon-do, soil of mixed forests, Q. serrata forest, N 37°23’36.50”, E 128°03’15.30”, 395 m asl.