Pseudorhynchelmis semernoyi, Martin, Patrick & Kaygorodova, Irina, 2008

Martin, Patrick & Kaygorodova, Irina, 2008, A new species of Pseudorhynchelmis Hrabě, 1982 (Clitellata: Lumbriculidae) from Lake Baikal, with re-descriptions of P. parva and P. olchonensis, Zootaxa 1938, pp. 23-39 : 30-32

Pseudorhynchelmis semernoyi sp. nov. ( Figure 3)

Type reference. Lycodrilus parvus Michaelsen, 1905: 18 –20 Fig. 3, partim

Synonymy. Rhynchelmis dissimilis Semernoy, 2004: 408 –412, partim, Fig. 228 (non figs 226, 227, 229).

Material examined. Zoologisches Museum Hamburg ( ZMUH), V6597. One sexually mature specimen preserved in ethanol, from a vial labelled as “ Limnodrilus parvus ; Mich.; Korotneff; Baikal-See” containing 3 specimens and one fragment, consisting in two species.

Yaroslavl State University, V. P. Semernoy’s collection. Whole-mounted specimens on Canada balsam, slides No 634, 69.34 and 874.

Holotype. Zoologisches Museum Hamburg ( ZMUH), V6597, slide 0 5.195.0 2 (partim) and vial V6597- 0 5.195.0 2 (partim). Mature specimen, incomplete (first 36 segments), anterior ends (head and sexual segments) cut along the midsagittal plane, right side stained in alcohol carmine and mounted in Canada balsam on slide 0 5.195.0 2, left side and tail left as they were and separately preserved in ethanol after examination in glycerine (V6597-05.195.02).

Type locality. Lake Baikal, Maloye More. Exact locality unknown.

Paratype. No paratype.

Etymology. The new species is dedicated to our colleague, Victor Petrovitch Semernoy (Yaroslavl State University, Russia), as a tribute to his contribution to the knowledge of oligochaetes of Lake Baikal.

Description. Medium-sized species, 9.9 mm (incomplete specimen), 37 segments, breadth 380 µm at widest (clitellum). Prostomium conical. Inconspicuous secondary annulation from III to VII, narrow annulus posterior ( Fig. 3C), intersegmental annulation well-marked in postclitellar segments. Well-marked, alveolate clitellum, extending over ½ IX–½ XIII. Brown tegument (fixed material). Two-simple pointed setae per bundle, sigmoid, with bent, slightly blunt tips, similar in dorsal and ventral bundles, 80–115 µm long, 4–5 µm thick, nodulus on the ectal third of seta ( Fig. 3B). Two pairs of modified genital setae in X, 173–177 µm long, 5 µm thick, elongate, straight, nodulus slightly proximal to the middle of shaft’s length ( Fig. 3B, gs). Setal length increasing from 80 to 115 µm in anteclitellar segments, slightly decreasing to a nearly constant length (82–86 µm) in postclitellar segments.

Dorsal pad of pharynx extending from II to IV, pharyngeal glands in IV – VI. Posterior sperm sacs ( Fig. 3, sps) extending from X to XIV, anterior sperm sacs not seen. Egg sacs short, reaching XII. One pair of spermathecal pores in VIII, opening behind ventral setal and slightly medially from setal line, close to septum 8/9, without modification of tegument into papillae. Long and tubular spermathecal duct ( Fig. 3A, spd) leading to voluminous ampullae ( Fig. 3A, spa), one ampulla filling the coelom in VIII, the other partially pushed backwards in IX. Sperm as an amorphous mass in ampullae. No communication between spermathecal ampullae and gut cavity.

Two pairs of testes in IX and X, respectively, attached ventrally to septa 8/9 and 9/10 ( Fig. 3A, t). Male pores paired, opening ventrally in line with ventral setae, near septum 10/11 ( Fig. 3A, mp). Two pairs of sperm funnels, on septa 9/10 and 10/11, respectively ( Fig. 3A, sf), posterior funnels taller than anterior ones and directed towards posterior sperm sacs. Two pairs of vasa deferentia ( Fig. 3A, vd). Anterior vas running upwards in order to skirt round testes and setal glands, before entering atria subapically. Posterior vas penetrating XI and making some loops before turning back in X, running along atrium proximal to this, and entering atrium subapically, opposite anterior vas. Vasa deferentia roughly of the same width all along their course (17 – 23 µm wide), not narrowed near atria. Cylindrical atria, 211 µm long, 98 µm wide, with large lumen (29 – 40 µm wide) and covered by thin muscular layer, relative to the atrium (5 µm; Fig. 3A, a). Atria restricted to X and tilted forwards in segment. Proximal part of atria pedunculated with small, pendant penes ( Fig. 3A, p). No rudimentary atria. Prostate glands constituted by large cells, grouped in petiolate bundles, separately opening onto atrium by means of short ducts ( Fig. 3A, pr). One pair of massive accessory copulatory glands ( Fig. 3A, cgl), surrounding penial setae, and opening ventrally through genital papillae, anterior to male pores by a distance similar to length of penial setae, roughly at the middle of X. Genital papillae are asymmetrical suckers, made up of enlarged epithelial cells; internal lip is twice the thickness of the external one ( Fig. 3A, gp).

Female pores paired, slightly median from setal line. Female funnels short, ciliated, attached to septum 11/12 ( Fig. 3A, ff). Ovaries in XI, paired, attached ventrally near septum 10/11 and extending to XII ( Fig. 3A, ov).

Remarks. Pseudorhynchelmis semernoyi sp. n. has quite distinctive morphological characters, both externally and internally, that makes it easily distinguishable from all other species of the genus. It posses a conical prostomium (all other species have a rounded prostomium), a well-marked clitellum with a honeycomb-like structure (vs. slightly differentiated and indistinct). The sucker-like genital papillae associated with penial setae are unique among Pseudorhynchelmis species. As in P. parva , P. semernoyi sp. n. has short, sacciform to cylindrical atria with large lumen. The latter character is unusual within the genus (as a rule, thick and glandular atrial lining cells reduce atrial lumen to a minimum). In contrast to P. p a r v a, however, P. semernoyi sp. n. has thin atrial musculature, in relation to atrial diameter.

Geographical distribution. To date, only known from Lake Baikal, Maloye More.