Olavius fidelis, 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 : 52-53

Olavius fidelis sp. nov.

Figure 4

Material examined

Holotype: SMNH Type Coll. 6390, whole­mounted specimen. Type locality: New Caledonia, Loyalty Islands, W side of Lifou, 31 m (Station NC00­22). Paratypes: SMNH Type Coll. 6391–6393, 3 specimens from type locality. Other material: SMNH Main Coll. 85112–85124, 13 specimens: 5 from type locality, 1 from NC00­8, 2

from NC00­3, and 5 from NC00­36.

Description

Length up to at least 3.4 mm, with up to at least about 30 segments; several specimens amputated. Width at XI, 0.15–0.23 mm. Body cylindrical. Prostomium rounded, in most specimens somewhat longer than wide. Pygidium rounded. Clitellum extending over 1/ 2X –1/ 2XII. Secondary annuli 8–14 per (postclitellar) segment. Somatic chaetae ( Fig. 4 A), bifid, with upper teeth thinner and shorter than lower, and each with conspicuous subdental ligament. These chaetae 25–35 m long, about 1–2 m thick, 2 per bundle throughout body; but totally absent in segment XI. Penial chaetae ( Fig. 4 B), 20–35 m long, about 1.2 m thick, 6–10 per bundle, straight, with single­pointed and strongly curved tips; chaetae not strictly parallel within bundle, but forming a somewhat arched row. Spermathecal pores paired, in lateral lines, anteriorly in X. Male pores paired, located more or less in line with ventral chaetae, in posterior part of XI; each pore is a rather conspicuous C­shaped slit ( Fig. 4 C, mp), along the convex side of which the row of penial chaetae can be seen ( Fig. 4 C, pc).

Male and female genitalia ( Fig. 4 C) paired. Vas deferens not muscular, about 10 m wide for most parts, longer than atrium, coiled, cilia not observed but probably present inside. Atrium small, round, about 35 m long, 24–31 m wide, with thin indistinct muscular layer, and granulated, compartmented inner epithelium, but cilia not observed on latter, lumen narrow. Two large, somewhat lobed, prostate glands present, one located anterior to and attached to ental part of atrium, other located posterior to and attached to ectal end of atrium by stalk. Atrium opening into inner end of small copulatory sac, latter with folded wall that may form a distinct papilla (pa); copulatory sac communicating with exterior through (male) pore ( Fig. 4 C, mp). Spermathecae ( Fig. 4 C, s) slender, totally 86–96 m long, with narrow ducts clearly set off from thin­walled, 17– 24 m wide, ampullae. Spermathecal vestibules may be present, but not obvious. Each spermathecal ampulla with a bundle of sperm.

Etymology

Named Olavius fidelis (Latin for loyal), for the Loyalty Islands where it was discovered.

Remarks

Olavius fidelis shares a unique combination of characters with three species from the Indian Ocean, O. manifae Erséus, 1986 ( Saudi Arabia), O. abrolhosensis Erséus, 1997 (Houtman Abrolhos Islands, Western Australia), and O. hamulatus Erséus, 1997 (Montebello Islands, Western Australia). All four species have bichaetal (somatic) bundles throughout the body, numerous small penial chaetae, small oval atria, copulatory sacs with folded walls, and slender spermathecae. The main distinguishing features are summarized in Table 2 . The new species appears most closely related to O. abrolhosensis , but differs from this species by its lack of muscles around the spermathecal vestibules.

In this species (as well as O. abrolhosensis ), the number of secondary annuli varies, but tend to be twice the number common in most other gutless species.

Distribution and habitat

New Caledonia (Loyalty Islands). Subtidal sand, 0.5–31 m depth.

Spermathecal vestibules if present, not obvious obvious, muscular if present, not obvious if present, not obvious

Figures

FIGURE 4. Olavius fidelis sp. nov. A) free­hand drawing of somatic chaeta, B) bundle of penial chaetae, C) horizontal view of spermatheca and male genitalia in segment X – XI.

Tables

TABLE 2. Morphological comparison between four closely related, Indo­West Pacific, forms of Olavius.

Secondary body annuli	7 per segment	7–14 per segment	6–7 per segment	8–14 per segment
Penial chaetae (length)	about 7–9 per bundle (about 25 µm)	about 6 per bundle (about 25 µm)	about 6 per bundle (about 25 µm)	6–10 per bundle (20–35 µm)
Spermathecal pores	latero­dorsal	mid­lateral	latero­ventral	mid­ventral
Atrial length	about 40 µm	about 35 µm	about 95 µm	about 35 µm