Chamaedrilus ozensis Torii, 2015, sp. nov.

Chamaedrilus ozensis sp. nov.

(Japanese name: Oze-amime-himemimizu, new) (Figure 2)

Type material. Holotype: One mature specimen, Mihon-en, Ozegahara mire, Katashina-mura, Tone-gun, Gunma Prefecture, Japan, N36°54’54.8’’, E139°11’53.7’’, 17 June 2008, T. Torii (NSMT-An 468). Paratypes: Five mature specimens, same data as holotype (NSMT-An 469–473).

Further material. Twelve whole-mounted mature specimens, same data as holotype, in the author’s collection.

Description. Live specimens grayish-white, fixed specimens 6.3–7.6 mm long, diameter 0.1–0.3 mm, 0.3 mm at clitellum. Segments 38–44. Chaetal formula 3 – 3: 3,3(2) – 3(2). Chaetae without nodulus and ental hook (Fig. 2 H,I). Lateral chaetae 46–48 µm in II, 48–50 µm in III, 62–64 µm in IV, 65–67 µm in V, 60–63 µm in postclitellar region. Ventral chaetae slightly longer than lateral chaetae. Ventral chaetae of II shortest, maximum length in V and postclitellar segments. Lateral chaetae of II, III shortest, in V and in postclitellar segments chaetae of same length. Chaetae of XII lacking in mature specimens. Epidermal gland cells small, in 3–5 rows or more or less scattered. Head pore at 0/1. Clitellum elevated conspicuously, from mid XI to XIII, XII–XIII prominent in live worms, granulocytes are packed with coarse granules not spherical but more like sand grains, irregularly scattered with clear interspaces (Fig. 2 B).

Brain 350–390 µm long, 1.5–2 times longer than wide, deeply incised posteriorly (Fig. 2 C). Three pairs of primary pharyngeal glands at IV–VI, all free dorsally, without ventral lobes, two pairs of compact secondary glands, situated ventrally in V and VI (Fig. 2 A). Oesophagus gradually merging into intestine. Chloragocytes present from IV, forming a dense layer from VI. Dorsal blood vessel origin in XV, occasionally in XIV, bifurcating at level of 0/1. Blood colorless in living specimens. Coelomocytes round or oval, some with lemon-like tips and cytoplasm finely grained and sometimes having a web-like structure (Fig. 2 G), 15–17 µm long, about 1/4 as long as postclitellar chaetae. Preclitellar nephridia three pairs from 6/7 to 8/9; anteseptal part of nephridium funnel only, about 35–45 µm long, postseptale about 100–120 µm long.

Sperm funnels small, cylindrical, in living worms about 105–110 µm long, 2–3 times longer than wide (Fig. 2 F). Collar equal or slightly wider than funnel body, but slightly smaller in fixed specimens. Sperm duct long and narrow, diameter 5–7 µm, coiled in XII, opening into a compact penial bulb. One or two eggs present at a time.

Paired spermathecal pores midlateral at 4/5, free spermathecae confined to V. Ectal ducts thick-walled, about four to five times the length of ampullae, ectal duct ca 87–95 µm long and 17–20 µm wide, with ectal swellings (Fig. 2 E). Ampulla spherical, dorsal to oesophagus in V, thin walled, 40–42 µm long, 1.2–1.5 times longer than wide, sperm extending into proximal part of ectal duct in most specimens.

Habitat. The species was present in the wet soil of the sphagnum mires.

Etymology. Named “ ozensis ” after the provenance of the species, Ozegahara mire, Japan.

Remarks. Three species of Cognettia have recently been transferred to Euenchytraeus, and Chamaedrilus has been found to be a senior synonym of Cognettia, therefore the remaining species should be attributed to Chamaedrilus (Martinsson et al. 2014). The two genera are distinguished by the presence of head nephridia in Euenchytraeus and their absence in Chamaedrilus. The present Japanese specimens are here defined as species of Chamaedrilus.

The following combination of characters is useful to identify the new species: 1) gradual transition from oesophagus to intestine; 2) spermathecae simple, without spherical enlargement; 3) sperm funnel 2–3 times longer than wide; 4) at least two types of coelomocytes. The new species resembles Chamaedrilus floridae (Healy, 1996), Chamaedrilus hibernicus (Healy, 1975), Chamaedrilus lapponicus (Nurminen, 1965) and Chamaedrilus zicsii (Dózsa-Farkas, 1989) in the following characters: three pairs of primary pharyngeal glands and two pairs of secondary glands, spermathecae confined to V, reproductive organs in the normal position for Enchytraeidae. They differ from Ch. ozensis sp. nov. in the following:

Ch. floridae: Coelomocytes round or oval, finely glandular with a prominent nucleus (round or oval, some with lemon-like tips and cytoplasm finely grained and sometimes having a web-like structure in Ch. ozensis). Sperm funnel 4–5 times longer than wide (2–3 times longer than wide in Ch. ozensis). Collar of sperm funnel slightly narrower than funnel body (equal or slightly wider than funnel body in Ch. ozensis).

Ch. hibernicus: Spermathecal ampulla elongate-ellipsoid (spherical in Ch. ozensis). Transition from oesophagus into intestine abrupt (gradual in Ch. ozensis). Number of chaetae in most bundles 2 (3 in Ch. ozensis). Sperm funnel oval, short, slightly longer than wide (2–3 times longer than wide in Ch. ozensis).

Ch. lapponicus: Spermathecal ampulla elongate-ellipsoid (spherical in Ch. ozensis). Spermathecal ectal opening with a moderate-sized gland (only swellings at the ectal opening in Ch. ozensis).

Ch. zicsii: Coelomocytes oval to oblong oval (round or oval, some with lemon-like tips and cytoplasm finely grained and sometimes having a web-like structure in Ch. ozensis). Spermathecal ampulla elongate-ellipsoid (spherical in Ch. ozensis). Spermathecal ectal opening with a moderate-sized gland (only swellings at the ectal opening in Ch. ozensis). Sperm funnel 4 times longer than wide (2–3 times longer than wide in Ch. ozensis).

One further species has been described as new from Japan, Chamaedrilus hayachinensis (Nakamura, 2001). It differs from Ch. ozensis in the presence of one enlarged chaeta in dorsolateral bundles V–VI, and in less compact spermathecal ampullae.