Caulleriella fucata Blake 2018, new species

Caulleriella fucata new species

Figure 24

Material Examined. Antarctic Peninsula, Palmer Archipelago, Anvers Island, Arthur Harbor, dock at Palmer Station, R / V Hero Sta. 721-5446, 29 Mar 1972, 64.775°S, 64.0683°W, 11m, holotype (USNM 1013891 and 4 paratypes (USNM 1013892); Sta. 731-1751, 16 Feb 1973, 64.775°S, 64.0683°W, 12 m, (1, USNM 1013941).

Description. A moderate-sized species, holotype 6.4 mm long, 0.5 mm wide across thickest part of middle body for 85 setigerous segments. Body generally thick throughout, with segments wider than long; posterior end sometimes expanded, but never narrower than middle body segments. Venter flattened, with shallow groove. Dorsal surface rounded or domed throughout. Entire body rust-colored, with dusky pigment on each segment; darker pigment on pygidium.

Prostomium short, triangular, bluntly rounded on anterior margin (Fig. 24 A–B); eyespots absent; nuchal organs elongate slits on posterior border with peristomium (Fig. 24A). Peristomium about as wide as long, tapering, merging anteriorly with prostomium to form conical pre-setigerous region or head; divided into two large rings by horizontal groove in middle (Fig. 24 A–B); dorsal crest absent. Peristomium followed by an achaetous segment (Fig. 24 A–B). Dorsal tentacles widely spaced, in groove on anterior edge of achaetous segment and posterior border of peristomium. First pair of branchiae immediately posterior to dorsal tentacles on posterior border of achaetous segment (Fig. 24B); subsequent branchiae in similar position dorsal to notosetae.

Noto- and neuropodia well developed, widely separated as typical of Caulleriella species (Fig. 24A). Notopodia set off from domed dorsal surface by grooves (Fig 24B); neuropodia with setae directed toward midventral groove. Notosetae all long capillaries, 8–10 per fascicle in anterior setigers, reduced to 3–5 in middle and posterior setigers; neurosetae of setigers 1–4(6) capillaries similar to those of notopodia, completely replaced by 8–10 short, curved bidentate hooks from setiger 5–7; hooks with blunt, thick main fang and thinner, more pointed apical tooth (Fig. 24D); hood or sheath not apparent.

Pygidium with 2–3 papillae on dorsal side of anus, and broad lobe ventrally (Fig. 24C).

Methyl Green stain. No stain retained.

Etymology. The specific name, fucata, is derived from the Latin fuco, for color, in reference to the pigmentation found on these worms.

Remarks. Caulleriella fucata n. sp. should not be mistaken for any other cirratulid species in Antarctic seas owing to its widely separated noto- and neuropodia, bidentate hooks, and darkly pigmented body. The species is most closely related to C. eltaninae n. sp. (see above) in having bidentate hooks limited to the neuropodia and by having the dorsal tentacles arising from a distinct achaetous segment. The two species differ in that the neuropodial hooks of C. fucata n. sp. begin on setigers 5–7 instead of 20–21 and the branchiae of C. fucata n. sp. begin on an achaetous segment instead of setiger 1. On a global basis, C. fucata n. sp. approaches C. zetlandica described by McIntosh (1911) in lacking dorsal hooks, but this species, recently redescribed by Woodham & Chambers (1994) does not have widely separated parapodial rami. This fact, plus the much-reduced nature of the teeth on the hooks and the lack of cinctures on the posterior end suggests that C. zetlandica should be referred to Tharyx.

Distribution. Antarctic Peninsula, 11– 12 m.