Doliodrilus chinensis, 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 : 290-292

Doliodrilus chinensis sp. n.

(figure 11)

Holotype. IHB HANA2000009 i, whole-mounted specimen

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

Paratypes. IHB HANA2000009 j–n, five specimens from type locality . SMNH Type Coll. 5485–5489, five specimens from type locality .

Other material. IHB HANA2000009 o–ae, 17 specimens from type locality . SMNH Main Coll. 43696–43712, 17 specimens from type locality .

Etymology. This species is known only from China so far, and its name is Latin for ‘of China’.

Description. Seven complete specimens 8.2–12.0 mm (holotype: 10.6 mm), 53–66 segments (holotype: 58). Diameter at XI 0.4–0.6 mm. Prostomium blunt or conical. Clitellum extending over XI–XII. Chaetae (figure 11A) bifid, with upper teeth usually thinner and shorter than lower, teeth sometimes equal in length. Chaetae 50–75 m m long, about 2.5 m m thick; two to four per bundle anteriorly, one to three per bundle in post-clitellar segments. Ventral chaetae absent in XI. Male pores paired, in line with ventral chaetae in posterior part of XI (figure 11E). Spermathecal pores paired, in line with ventral chaetae in anterior part of X.

Pharyngeal glands in IV– V, those in V sometimes indistinct or absent. Chloragogen cells from VI onwards. Oesophagus in IX barrel-shaped, thick-walled and granulated, with chloragogen cells absent, scarce or (sometimes) abundant; semi-embedded blood plexus permeating entire region, with regular transverse vessels and less regular longitudinal ones.

Male genitalia (figure 11E) paired. Vas deferens (figure 11E: vd) shorter than atrium, 80–100 m m long, about 16 m m wide, entering atrium apically. Atrium (figure 11E: a) altogether somewhat spindle-shaped, 205–235 m m long, 31–43 m m wide, opening to exterior through simple pore. Ental end of atrium neither thinwalled nor dilated, somewhat tapering off on to vas. Prostatic pad (figure 11E: ppd) round, 44–53 m m long, ventrally attached ental to middle of atrium; pad bulging out from atrium. Prostate gland (pr) large, with small nuclei and large nucleus-like bodies, latter oval to round, maximally 14 m m long and 12 m m wide. Ectal part of atrium simple, with neither blind sac nor dilatation (figure 11E). Sperm sac large, extending through two to five segments in IX–XIII. Egg sac when developed, restricted to one segment within XII–XIII. Spermathecae (figure 11B–D) large; ducts 40–80 m m long, 24–51 m m wide, with small ectal vestibules; ampullae oval and thinwalled, 175–195 m m long, 65–115 m m wide, sperm in lumina usually as dense, somewhat sea-horse-shaped spermatozeugmata (figure 11B, C), sometimes in random masses (figure 11D).

Remarks. This new species is characteristic, as it usually has somewhat sea-horseshaped spermatozeugmata. Considering the simple male ducts, with rather short vasa deferentia, D. chinensis sp. n. shows similarities to, and is possibly closely related to, D. bidolium sp. n. However, in addition to the difference with regard to the oesophageal modifications (see Remarks for D. bidolium ), the prostatic pads of D. chinensis are situated more entally on the atria, and the male pores are located posteriorly in segment XI, not in mid-XI as in D. bidolium .

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