Rhyacodrilus stephensoni Černosvitov, 1942

Cui, Yongde, He, Xuebao, Peng, Yu & Wang, Hongzhu, 2015, Records of Naididae and Lumbriculidae (Clitellata) from Tibet, China, with description of a new species of Nais, Zootaxa 3956 (4), pp. 513-530 : 525

16. Rhyacodrilus stephensoni Černosvitov, 1942

( Figure 6 )

Rhyacodrilus stephensoni Černosvitov, 1942: 284 –285, Liang & Xie 1992: 196 –197.

Material. 1 spm, whole-mounted in Canada balsam, from ST59, 4 specimens in 10% formalin from ST59 and ST61.

Description. Length 7.8 mm, width in X 0.37 mm, 35 segments. Coelomocytes abundant. Prostomium cylindrical. Pharynx in III–IV. No hairs. Chaetae bifid, distal tooth shorter or equal to proximal, nodulus distal. Chaetae ( Fig. 6 B) of anterior segments 3–4 per bundle, posteriorly 2–4 (3) per bundle. Vas deferens ( Fig. 6 C, vd) short, 22.5 Μm in diameter, wall 7.5 Μm thin, attached to atrium subapically. Atrium ( Fig. 6 C, at) oval-like, ampulla thickly covered with diffuse unicellular prostate gland ( Fig. 6 C, pr). Pseudopenes ( Fig. 6 C, pe) present, 35 Μm in diameter. Spermathecae ( Fig. 6 C, sa) oval-shaped, walls of ampulla 7.5–12.5 Μm thin. Duct ( Fig. 6 C, sd) short, 35 Μm long, 47.5 Μm in diameter, 20Μm in its thick wall. Spermathecal chaetae unmodified, 4 per bundle, penial chaetae ( Fig. 6 A) straight, bifid, with a very short distal tooth, 3 per bundle.

Remarks. This species was recorded by Stephenson (1909) for the first time as Limnodrilus sp. in Tibet, and then Černosvitov (1942) redescribed it, recognized it as a new species, and transferred it to the genus Rhyacodrilus . This species is also distributed in terrestrial habitats of Tianmu Mountain in Zhejiang Province ( Liang & Xie 1997).

Figures

FIGURE 6. Rhyacodrilus stephensoni Černosvitov, 1942. A. Spermathecal chaeta. B. Dorsal chaeta. C. Lateral view of male duct and spermatheca in segments X – XI. Scale bars: A – B 20 Μm, C 80 Μm.