Doliodrilus longidentatus, 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 : 276-278

Doliodrilus longidentatus sp. n.

(figure 3)

Doliodrilus tener Erséus (partim); Erséus, 1990a: 287–288, figure 11C, D, H, K; Gustavsson and Erséus, 1999: 470–471, figure 1d–f.

Non Doliodrilus tener Erséus, 1984: 159–160 , figure 15.

Holotype. SMNH Type. Coll. 5461, whole-mounted specimen.

Type locality. China, Hong Kong, mangroves at Mai Po, edge of dredged channel, mid-intertidal mud (Station HK86-26=‘Station 70’ in Erséus, 1990a); 9 April 1986, coll. C. Erséus.

Paratypes. SMNH Type. Coll. 5462–5466, five specimens from type locality . SMNH Type Coll. 5467–5468, two (sectioned) specimens from type locality . SMNH Type Coll. 5469–5470, two from Hong Kong, Deep Bay , mudflat just off mangroves at Mai Po marshes ( Station HK86-25=‘ Station 69’ in Erséus, 1990a); 9 April 1986, coll. C. Erséus. SMNH Type Coll. 5471, one specimen from Hong Kong, Deep Bay , Tsim Bei Sui , intertidal mudflat ( Station HK86-31=‘ Station 76’ in Erséus, 1990a); 10 April 1986, coll. C. Erséus.

Other material. SMNH Main Coll. 43678–43679, two specimens from Hong Kong, Deep Bay , mangroves at Mai Po marshes, intertidal mud; 22 April 1989, coll. A. Mackie and G. Oliver. IHB HANA2000023 a, one specimen from Hainan Island , Station HU 00-14B .

Etymology. The specific name longidentatus is Latin for ‘with long teeth’, and refers to the long upper teeth of the chaetae.

Description. No complete specimen in material from Hong Kong. Hainan specimen 9.3 mm long, about 50 segments. Diameter at XI 0.4–0.6 mm. Prostomium conical. Clitellum well developed over XI–XII. Chaetae bifid, with upper teeth 2–2.5 times as long as, and as thick as, lower (figure 3A). Chaetae 70–85 m m long, about 3 m m thick; (two) three to four (five) per bundle anteriorly, two (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 3B). Spermathecal pores paired, in line with ventral chaetae in anterior part of X.

Pharyngeal glands well developed in IV– V. Chloragogen cells from VI onwards. Oesophagus in IX barrel-shaped, thick-walled and granulated, without or with few chloragogen cells; semi-embedded blood plexus permeating dorsal region, with regular transverse vessels and less regular longitudinal ones.

Male genitalia (figure 3C, D) paired. Vas deferens (figure 3C, D: vd) 160–255 m m long, 19–22 m m wide, entering atrium apically. Atrium totally 190–340 m m long, 14–48 m m wide; ental part of ampulla thin-walled and dilated, ectal part tubular and with more nuclei (figure 3C, D: aa), but without clusters of dense slender nuclei around prostatic pad; when atrium not stretched (figure 3C), dorsal wall opposite to prostatic pad somewhat thicker than other parts of ampullar wall. Prostatic pad (figure 3C, D: ppd) round, 17–24 m m long, bulging out from atrial ampulla, usually situated at middle or ectal to middle of atrium (figure 3C), but slightly ental to middle of atrium when latter is stretched (figure 3D). Prostate gland (figure 3C, D: pr) medium-sized, with small nuclei and large nucleus-like bodies, latter oblong to round, maximally 14 m m long, 10 m m wide. Atrial duct (figure 3C, D: ad) with (1) large posterior blind sac (bs), 95–120 m m long, 15–40 m m wide, and (2) short efferent duct (ed), about 35 m m long, 31-48 m m wide. Sperm sac in one to two segments within IX–XI, when developed at all. Egg sac in one to two segments within XI–XIII, when developed. Spermathecae (figure 3B) variable in size; ducts about 50 m m long, 22–31 m m wide, with ectal vestibules; ampullae oblong, 95–205 m m long, 60–75 m m wide, with sperm masses in lumina.

Remarks. This species was previously regarded as a form of D. tener (Erséus, 1990a) , but as the result of a more careful assessment of the male genital ducts, it is now recognized as a separate taxon. It is distinguished from D. tener by the distinctly longer upper teeth of its chaetae, the absence of clusters of slender nuclei in the atria, the more ectal location of the prostatic pads on the atria, and, generally, the larger size of external and internal structures. The long upper teeth on the chaetae are shared by D. ciliatus sp. n. (described below), but otherwise this feature discriminates D. longidentatus from all congeners.

The specimen from Hainan was studied from a dorsal view, and its identification is mainly based upon the features of the chaetae and the absence of nuclei clusters.

Distribution and habitat. Southern China. Usually intertidal in mangroves, clay and mud.