Doliodrilus brachyductus, Wang & Erséus, 2004

Wang, Hongzhu & Erséus, Christer, 2004, New species of Doliodrilus and other Limnodriloidinae (Oligochaeta, Tubificidae) from Hainan and other parts of the north-west Pacific Ocean, Journal of Natural History 38 (3), pp. 269-299 : 287-289

Doliodrilus brachyductus sp. n.

(figure 9)

Holotype. IHB HANA200009 ak, whole-mounted specimen.

Type locality. China, southern Hainan, brackish-water pond near Teng Hai (E of Sanya City) (Station SY00-6).

Etymology. The specific name brachyductus is Greek for ‘with short duct’, and alludes to the short, simple male duct.

Description. Holotype 6.7 mm long, 53 segments. Diameter at XI about 0.2 mm. Prostomium blunt. Clitellum inconspicuous. Chaetae bifid, with upper teeth as long as but much thinner than lower (figure 9A). Chaetae 45–50 m m long, about 2.5 m m thick; two to three per bundle anteriorly, (one) two to three per bundle in postclitellar segments. Ventral chaetae absent in XI. Male pores paired, in line with ventral chaetae, posterior to middle of XI (figure 9B). Spermathecal pores paired, in line with ventral chaetae, anterior to middle of X (figure 9B).

Pharyngeal glands in IV– V. Chloragogen cells from VI onwards. Oesophagus in IX barrel-shaped, thick-walled and granulated, with few chloragogen cells; semiembedded blood plexus permeating entire region, with regular transverse vessels and less regular longitudinal ones.

Male genitalia (figure 9B) paired. Vas deferens (figure 9B: vd) longer than atrium, about 100 m m long, 5 m m wide, entering atrium slightly subapically. Atrium tubular or somewhat spindle-shaped, ental part (figure 9B: aa) somewhat dilated but not thin-walled, ectal part (ead) distinctly dilated but opening to exterior through simple pore; atrium totally 70–80 m m long, 15–17 m m wide for most part, 25–30 m m wide at ectal dilatation. Prostatic pad (figure 9B: ppd) oval to round, 22–24 m m long, ventrally attached to atrium, distinctly ental to middle of latter. Prostate gland (pr) small, with oval nuclei, latter maximally 5 m m long, 3 m m wide. Spermathecae (figure 9B: s) small; ectal ducts short, indistinct; ampullae oval and thick-walled, 50–95 m m long, 25–45 m m wide, each with a few spermatozoa in lumina.

Remarks. This new species resembles D. fibrisaccus sp. n. in certain aspects of the atria, i.e. the ectal parts are dilated, the ental parts are short, the prostatic pads are entally located, and the prostate glands are small. In D. brachyductus sp. n., however, the ectal dilatations of the atria have no distinct musculature, as opposed to the thick muscular layers in D. fibrisaccus . Moreover, the spermathecal ducts of D. brachyductus are indistinct, whereas those of D. fibrisaccus are about as long as the spermathecal ampullae (cf. figure 8B, D).

Distribution and habitat. Known only from type locality, southern China. Brackish-water, muddy sand.