Potamothrix alatus hazaricus Timm & Arslan

Timm, Tarmo, Arslan, Naime, Rüzgar, Melih, Martinsson, Svante & Erséus, Christer, 2013, Oligochaeta (Annelida) of the profundal of Lake Hazar (Turkey), with description of Potamothrix alatus hazaricus n. ssp., Zootaxa 3716 (2), pp. 144-156 : 148-150

Potamothrix alatus hazaricus Timm & Arslan , n. ssp.

( Fig. 2 )

Holotype. VLS, Types-32.1: sexually mature specimen as a whole mount, Lake Hazar, station 7, depth 20 m, 4.06.2012. Collected by N. Arslan.

Type locality. Lake Hazar in eastern Anatolia ( Turkey), 39.2 °E, 38.2 °N, 1248 m a.s.l.

Paratypes. All three from Lake Hazar, collected by N. Arslan. VLS, Types-32.2: cross sections on 3 slides, station not established, depth 50 m, 20.07.2007. ESOGU, (H) No 1: one sexually mature specimen in a whole mount, station 9, depth 100 m, 0 4.06.2012. SMNH Type 8528: one whole-mounted, sexually mature specimen (CE 14301 in Table 1 ), station 8, depth 65 m, 04.10.2011; with sequenced COI barcode, GenBank Acc. No. KF366623 .

Other material. About 280 specimens, all from Lake Hazar, studied as whole mounts; seven of them with sequenced barcodes, deposited in SMNH, see Table 1 . Further 77 whole-mounted specimens on 17 slides, and 8 serially sectioned specimens are deposited in VLS; the rest of material in ESOGU.

Etymology. Named after Lake Hazar, the type locality.

Description. Length of sexually mature individuals after fixation in 96% ethanol 10–21 mm, most often 12–13 mm; after fixation in formalin or 70% ethanol, ranging between 11–26 mm, in single cases 33 or 34 mm. Segment number from 45 to about 130, the maximum number not always in the longest individuals since the tail portion sometimes with short, just developing segments. Body wall smooth and transparent. Prostomium short, conical, separated from peristomium by a groove. Preclitellar portion of body widening gradually, in segment VIII 0.5–1.3 mm wide, the genital segments usually wider. Postclitellar portion gradually narrowing to 0.25–0.35 mm while intersegmental furrows become deeper. The genital segments X–XI almost always bear wide, lateral wing-like outgrowths produced by contraction of dorsoventral muscles. These "wings" begin anteriorly in the dorsolateral part of X as narrow strips (Figs 2.1, 2.8), proceed diagonally downwards, and continue in XI as thick lateral folds directed downwards and containing many internal organs; usually they do not reach XII. As a result, the ventral side of segment XI appears deeply concave in fixed specimens (Figs 2.1, 2.9, 2.10). Body dorso-ventrally flattened and thin in X–XI, the thinnest between X and XI where a distinct transversal groove crosses the ventral side (here body often only about 0.28–0.45 mm high). Spermathecal pores in X lateral, inconspicuous. Male pores in line of ventral chaetae, large, sometimes up to 100 Μm wide when penes are protruded. Both spermathecal and male pores open under the edges of the "wings". Female pores not observed. Clitellum in XI–XII, thin.

Hair chaetae (Fig. 2.2) present along the whole body, smooth, in preclitellar segments (0,1)2–3(4) per bundle, (100)250–450 Μm long and about 2 Μm thick, longest in IV–VI, shortest in II. In postclitellar segments 0–2 hair chaetae, up to 160–190 Μm long. Pectinate chaetae (Fig. 2.3) in preclitellar segments with equally long teeth and several short intermediate denticles, (2,3)4–6 per bundle, (80)100–170 Μm long and 3.5 Μm thick, longest in IV– VII, shortest in II. In postclitellar dorsal bundles pectinates replaced by (1,2)3(4) small bifid chaetae, 80–120 Μm long. Preclitellar ventral chaetae (Fig. 2.4) bifid, with slightly longer and thinner upper tooth, (2,3)4–6(7,8) per bundle. Postclitellar ventral chaetae (Fig. 2.5) 3–4(5) per bundle, 100–140 Μm long, with equal teeth, similar to the dorsal ones.

Spermathecal chaetae (Fig. 2.6) in X, one on each side, sitting in thick (50–73 Μm) muscular-glandular pouches; sometimes absent, even in mature individuals. These chaetae straight or slightly sigmoid with bent Chloragogen tissue beginning in VI, the wide midgut in VIII. Dissepiments thin. Lateral vessels forming loops in ventral side of IV–VII; single dilated lateral vessels observed only in two sectioned individuals, in VII or VIII, but no regular "hearts". Testes in X, ovaries in XI. Sperm sacs anteriorly often reaching IX (or even VIII) and posteriorly XI–XII, egg sac with eggs sometimes as far as XIV or XV. Spermatozoa in X and in sperm sacs organized in large, spindle-shaped bundles (Figs 2.8, 2.9). Male funnels at the anterior side of dissepiment 10/11, large and of variable shape, their posterior end sometimes piercing the dissepiment and reaching XI. Vasa deferentia (Figs 2.7, 2.9) straight, ascending from male funnels, and about 200–300 Μm long and 32–60 Μm wide, wall about 10 Μm thick, and lumen densely ciliated.

Paired atria tripartite (Fig. 2.7). The first part in XI (Fig. 2.7: a1) short but curved or winding, about 20–85 Μm wide, with lumen only 5–6 Μm wide, and consisting of dark-staining glandular cells similar to those of the prostate gland. Prostate gland attached to the first part of atrium and sometimes surrounded by a loop of the latter, slightly lobate, up to 125–250 Μm in diameter. Second part of atrium (Figs 2.7, 2.10: a2) several times longer than body diameter, forming loops in the coelomic cavity of XI–XII; diameter variable (37–110 Μm), wall consisting of vacuolized epithelium, lumen irregularly wide. Third part of atrium (Figs 2.7, 2.9, 2.10: a3) localized vertically in the lateral part ("wing") of XI, 200–400 Μm long and 45–170 Μm wide, with dense wall consisting of narrow epithelial cells; its lumen 10–100 Μm wide, sometimes winding; the external muscle layer about 3 Μm thick. This terminal portion of atrium continuous with a 100–200 Μm long and proximally 65–145 Μm wide conical penis consisting of similar tissue; penis lumen sometimes dilated up to a width of 45 Μm. Penis usually retracted into spacious penial sac but often partially or completely protruded from the male pore. Penial sac 100–175 Μm wide in its proximal portion, with an inner circular fold near the base of the penis (Figs 2.7, 2.10).

Paired spermathecae in X. Spermathecal ampulla roundish or bilobate (when extending above or below intestine into opposite side), usually about 300–400 Μm, maximally 600–700 Μm wide, with thin (5 Μm) and smooth wall when full of spermatozoa but with thicker (up to 20 Μm) and internally folded wall in slack portions (Fig. 2.8). Spermatozeugmata numerous, spindle-shaped, 55–105 Μm wide, longer than the diameter of ampulla. The filled ampullae can be pressed into XI. Spermathecal duct short (about 300 Μm), up to 100 Μm wide in proximal part and narrowing to 25–40 Μm distally, distinctly three-layered, with lumen of variable width. The funnel-shaped spermathecal pores lie in the posterior part of X, lateral to the spermathecal chaetae and below the body "wings".

Ecology. A taxon with mass occurrence in the strongly alkaline Lake Hazar, abundant in the profundal at all depths. Not known in any other water bodies.

Figures

FIGURE 2. n. ssp. 1. External view of forebody. 2. Hair chaeta. 3. Pectinate chaeta 4. Anterior ventral chaeta. 5. Posterior ventral chaeta. 6. Spermathecal chaeta. 7. Scheme of male duct, freehand drawing. 8. Cross section of the segment X. 9. Cross section of the anterior part of XI. 10. Cross section of the posterior part of XI. a 1, a 2, a 3 — consecutive parts of atrium, bv—blood vessel, i—intestine, mf—male funnel, mp—male pore, pr—prostate gland, ps—penial sheath with penis, sp—sperm bundles in body cavity, spt—spermathecal ampulla with spermatozeugmata, vd—vas deferens, w—lateral " wings " formed by the body wall.