Tubifex conicus He, Wang & Cui, 2012

Cui, Yongde, 2017, Four species of Tubifex Lamarck (Annelida: Oligochaeta: Naididae) from Tibet, China, Zootaxa 4320 (2), pp. 366-378 : 371-372

Tubifex conicus He, Wang & Cui, 2012

( Figs 7–8 )

Tubifex conicus He, Wang & Cui, 2012: 160 –162, Fig. 1 .

New material. IHB XZ20150602 a–e, 5 mature specimens, whole-mounted in Canada balsam, from Gyaring Co, preserved in IHB, CAS. Gyaring Co (30°58' 43″N, 88°28′04″E), a lake located in northern Tibet of China, ca. 4,648–4,659 m asl. Water depth 11–37 m, water temperature 6.3–8.9°C, pH 6.3–8.9, dissolved oxygen 7.3–7.7 mg / L, conductivity 323–329 µs/cm. Collected by Yongde Cui and Baoqiang Wang on 2 June 2015.

Description. Length 6.1–11.6 mm, width at genital segments X–XI 0.28–0.42 mm. Segments 38–65. Prostomium obtuse. Clitellum inconspicuous. No coelomocytes. Dorsal chaetae (0) 1 hair and 1–4 bifids per bundle. Hairs serrate, posteriorly generally absent ( Fig. 7A, B ). Dorsal bifids pectinate, upper and lower tooth subequal, with 2–3 fine intermediate teeth ( Fig. 7A ). Ventral chaetae bifid, 3–4 per bundle anteriorly, 2 per bundle posteriorly, upper tooth slightly longer than lower, with (0) 1–2 fine intermediate teeth ( Fig. 7C, D ). Ventral chaetae in X present, unmodified. Ventral chaetae in XI absent. Male pores paired in line with ventral chaetae, middle to posterior of XI.

Chloragogen cells from VI onwards. Male genitalia paired in X–XI. Sperm funnel cup-shaped, 20 µm long, 40 µm wide ( Fig. 8A,B : sf). Vas deferens 400–560 µm long, 12–15 µm wide, nearly 3–4 times as long as atrium, ciliated throughout and entering atrium apically ( Fig. 8A, B : vd). Atrium spindle-shaped, 120–160 µm long, maximally 32–40 µm wide ( Fig. 8A, B : at). Ejaculatory duct present. Prostate gland solid, 80–84 µm long, 60–64 µm wide, attached to ental portion of atrium ( Fig. 8A, B : pr). Penis inconspicuous, surrounded by cuticular, symmetrical and funnel-shaped penial sheath. Penial sheath 36–40 µm long, 48–56 µm wide at ental end ( Fig. 8A, B, C : ps). Testes paired in X, immediately behind septum 9/10. Ovaries paired in XI, immediately behind septum 10/11. Spermathecae absent.

Remarks. The main difference of our redescription from T. conicus as originally described ( He et al. 2012) is the absence of spermathecae. However, after our reinvestigation of the type series (holotype and paratypes), we are sure that the testes of T. conicus were mistaken for spermathecae in the original description. Further slight differences between the descriptions concern thickness of atrial epithelium (thicker in the redescription) and penial sheaths (thicker in the original description). They may relate to the stage of maturity or to different modes of interpretation of observations. The size and shape of atria in the original observation and this research are about the same. Penial sheaths appear to have a thick cuticle laterally in the holotype, but when comparing type series and our material, we found no significant differences in penial sheath thickness.

Distribution and habitat. Known from Yamdrok Yumco (Lake Yamzho Yumco), Gyaring Co, Chargut Co, Uruni Co, Chikui Co, Amdo Tsonak Co, Tibet, China. All these lakes are located at above 4,000 m asl in Tibet. Gyaring Co, the locality of present redescribed materials, is about 300 km from the holotype locality of T. conicus, Yamdrok Yumco. Freshwater and brackish water.

Figures

FIGURE 1. Tubifex laxus n. sp., SEM micrographs. A. Lateral view of anterior body. B. Hairs in IV. C. Hair chaeta and palmate chaeta in XII. D. Dorsal palmate chaetae in XII. E. Ventral chaetae in IV. F. Ventral chaetae in XIII. Scale bars: A. 500 µm; B, C. 10 µm; D – F. 20 µm.

FIGURE 7. Tubifex conicus He, Cui & Wang, 2012, SEM micrographs. A. Dorsal chaetae in VII. B. Hair chaeta in a posterior segment. C. Ventral chaetae in II. D. Ventral chaetae in a posterior segment. Scale bars: A – D. 20 µm.

FIGURE 8. Tubifex conicus He, Cui & Wang, 2012. A, B. Male genitalia, lateral view. C. Penial sheath. Scar bars: A – C. 100 µm.