Caulleriella fimbriata Blake 2018, new species

Caulleriella fimbriata new species

Figure 23

Material examined. Southern Ocean, Powell Basin, R / V Polarstern, ANDEEP III (ANT-XXII/3), Sta. 67/150-8, 20 Mar 2005, 61°48.56ʹS, 47°27.48ʹW, MUC, 1884 m, holotype (SMF 24908).

Description. Holotype small, threadlike, complete in three pieces, 3.4 mm long, 0.1 mm wide, with 60 setigerous segments. Body cylindrical throughout, without dorsal and ventral grooves; anterior segments to about setiger 14 wider than long (Fig. 23A), then becoming rounded, moniliform in middle body, becoming narrow again in far posterior segments; body tapering to triangular pygidium bearing a single anal cirrus (Fig. 23B). Parapodia of first four setigers close to one another, then these separating with noto- and neuropodia becoming widely separated from one another along rest of body (Fig. 23A). Color in alcohol tan with diffuse brown pigment on a few anterior segments.

Prostomium triangular, tapering to rounded tip; with rounded dome-like dorsal crest with glandular band on posterior margin (Fig. 23A); eyespots absent; nuchal organs narrow slits anterior to band of glands (Fig. 23A). Peristomium enlarged, inflated, about as long as first three setigers, without annular rings (Fig. 23A); with two short lobes representing stumps of dorsal tentacles near posterior margin (Fig. 23A). First pair of branchiae on setiger 1 posterior to notosetae; subsequent branchiae from same location, continuing to about setiger 20.

Parapodia reduced to simple mounds from which setae arise. Notosetae include 4–6 simple capillaries on first 15–20 setigers; bidentate hooks from setiger 23, with 3–4 hooks and 1–2 thin capillaries per notopodium continuing to posterior end; last 1–2 notopodia with hooks long, acicular, lacking apical tooth. Neurosetae include 3–4 capillaries on setigers 1–5, with bidentate hooks from setiger 6; hooks 2–3 per neuropodium accompanied by 1–2 capillaries. Hooks gently curved, with short, pointed apical tooth surmounting sharply pointed main fang (Fig. 23C); hooks without hood or crest on shaft.

Etymology. The epithet is from fimbria, Latin for thread, referring to the threadlike body of this species.

Remarks. Caulleriella fimbriata n. sp., C. antarctica, and C. kacyae n. sp. are three small, threadlike species that all occur in deep-water Antarctic sediments. Caulleriella fimbriata n. sp. is distinguished from the other two species in having only a single peristomial ring instead of two or three, and a single anal cirrus instead of two. Additional details that differ between these three species and others are found in Table 2 in the Discussion.

Habitat. The Powell Basin is known as a dynamic environment based on currents and sedimentation patterns. Surficial sediments collected as part of the ANDEEP III survey at a site near the type-locality of Caulleriella fimbriata n. sp. consisted of dark greyish brown, poorly sorted mud with sand (3%), silt (66%), and clay (31%) (Howe et al. 2007).

Distribution. Southern Ocean, Powell Basin, 1884 m.