Olavius amplectens, Erséus, Christer & Bergfeldt, Ulrika, 2007

Erséus, Christer & Bergfeldt, Ulrika, 2007, Six new species of the gutless genus Olavius (Annelida: Clitellata: Tubificidae) from New Caledonia, Zootaxa 1400, pp. 45-58 : 49-50

Olavius amplectens sp. nov.

Figure 2

Material examined

Holotype: SMNH Type Coll. 6373, whole­mounted specimen

Type locality: New Caledonia, Loyalty Islands, Lifou, Baie du Santal, 18 m (station NC00­5).

Paratypes: SMNH Type Coll. 6374–6380, 7 specimens: 2 from type locality, 1 from NC00­29, and 2 from each of NC00­35 and NC00­38.

Other material: SMNH Main Coll. 85069–85080, 12 specimens: 1 from each of type locality, NC00­8, NC00­35 and NC00­37, 2 from NC00­29, and 6 from NC00­38.

Description

Length 1.3–2.4 mm, with 15–22 segments. Width at XI, 0.10–0.18 mm. Body cylindrical. Prostomium rounded. Pygidium variable, with rounded tip. Clitellum extending over X–XII. Body wall not conspicuously annulated but often 15 small secondary annuli visible per (postclitellar) segment. Somatic chaetae ( Fig. 2 A) long, protruding conspicuously from body­wall, bifid, with upper teeth thinner and shorter than lower, and each with conspicuous subdental ligament. These chaetae 31–39 m long, about 2 m thick, 2 per bundle throughout body. Penial chaetae ( Fig. 2 B, pc) slender, 3 per bundle, more or less parallel, 50–70 m long, about 2 m thick, with single­pointed hooked tips. These chaetae characteristically protruding (at least in all fixed specimens) from body ventrally in XI. Spermathecal pores paired, located in line with dorsal somatic chaetae, in middle of segment X. Male pores paired, located in line with ventral chaetae, in posterior part of XI.

Male and female genitalia ( Fig. 2 B) paired. Vas deferens thin but muscular, 7–10 m wide for most parts, longer than atrium, coiled, gradually widening into atrium, cilia not observed but probably present inside. Atrium oval, 35–60 m long, about 20–30 m wide, with thin indistinct muscular layer, and granulated compartmented inner epithelium, but cilia not observed on latter, lumen narrow. Two, somewhat lobed, prostate glands present, one located anterior to and attached to ental part of atrium, other located posterior and attached to ectal end of atrium by stalk. Atrium opening into inner end of a complex copulatory sac with heavily folded wall; this sac communicating with exterior through small (male) pore (pore not shown in Fig. 2 B, as it is hidden under copulatory sac). Spermathecae ( Fig. 2 B, s) somewhat curved, thin­walled, totally 85–135 m long, 35–50 m wide, duct short but well set off from ampullae. Each spermatheca with somewhat bundled sperm.

Etymology Named Olavius amplectens (Latin for clasping) for its long penial chaetae, which protrude conspicuously from body wall in segment XI.

Remarks

In this species, the spermathecal pores are located more or less in line with the dorsal somatic chaetae in the middle of segment X, and the penial chaetae are slender, multiple (more than two per bundle), sigmoid, and conspicuously hooked, a combination of features that make it most similar to O. cornuatus Davis, 1984 . The latter is a Northwest Atlantic species (known only from off Massachusetts, USA; Davis 1984), and the two taxa are not necessarily closely related. Differences between them are that O. amplectens has (i) only two somatic chaetae per bundle ( O. cornuatus has up to four chaetae per bundle in anterior segments), and (ii) less developed copulatory organs (in O. cornuatus , the outer ends of the atria appear like large protrusible penes). The most striking feature of this new species, however, is that the somatic as well as penial chaetae protrude from the body wall, at least more so than noted for any other gutless species known to date.

Distribution and habitat

New Caledonia (Loyalty Islands). Subtidal, more or less heterogeneous sand, 4–40 m depth.

Figures

FIGURE 2. Olavius amplectens sp. nov. A) free­hand drawing of somatic chaeta, B) somewhat lateral view of spermatheca and male genitalia in segments X – XI.