Caulleriella antarctica Hartman, 1978

Blake, James A., 2018, Bitentaculate Cirratulidae (Annelida, Polychaeta) collected chiefly during cruises of the R / V Anton Bruun, USNS Eltanin, USCG Glacier, R / V Hero, RVIB Nathaniel B. Palmer, and R / V Polarstern from the Southern Ocean, Antarctica, and off Western South America, Zootaxa 4537 (1), pp. 1-130 : 40-41

Caulleriella antarctica Hartman, 1978

Figure 19

Caulleriella antarctica Hartman, 1978:164–166 , fig. 17; Rozbaczylo 1985: 151.

Tharyx antarcticus: Blake & Narayanaswamy 2004: 1806, 1813 (in part).

Material Examined. Antarctica, Weddell Sea, USCG Glacier Sta. 69-1, 24 Feb 1969, 74°28.1ʹS, 30°31.7ʹW, 513 m, holotype ( USNM 46777 ) and 14 paratypes ( USNM 46778 ); Sta. 69-2, 25 Feb 1969, 75°31ʹS, 30°08ʹW, 412 m (2, USNM 46781 ); Sta. 68-1, 06 Feb 1968, 70°07ʹS, 39°38ʹW, 650 m (8, USNM 46779 ); Sta. 68-5, 09 Feb 1968, 76°00ʹS, 55°00ʹW, 400 m (10, USNM 46780 ).— Weddell Sea , E of Antarctic Peninsula, R / V Polarstern, ANDEEP II (ANT XIX/4 ) , Sta. PS 61/133-6, 07 Mar 2002, 65°20.18ʹS, 54°143.6ʹW, MUC, 1120 m (1, SMF 24907).— Ross Sea , McMurdo Sound, Ross Island, Cape Evans, coll. ca. 10 m in gravelly sand, scuba, by Stacy Kim , 1 specimen ( USNM 1013671 ) .

Description. A small, threadlike species, holotype complete, 4.8 mm long, 0.2 mm wide for 33 setigers; one paratype 6 mm long, 0.2 mm wide for 43 setigers. Peristomium and first 3–5 setigers inflated with segments wider than long ( Fig. 19 A–B), thereafter segments becoming longer, beadlike; posterior end tapering to narrow, blunted pygidium; a complete Weddell Sea specimen with one lobe on pygidial segment; Ross Island and ANDEEP II specimens with two distinct cirri ( Fig. 19C ). Body segments with noto- and neuropodia widely separated. Color in alcohol: light tan.

Prostomium short, triangular, as wide at base as long ( Fig. 19A ), bluntly pointed on anterior margin, eyespots absent; peristomium elongate, about as long as wide, weakly divided into two rings ( Fig. 19 A–B). Paired dorsal tentacles arising from medial position at posterior margin of peristomium; first pair of branchiae arising lateral and posterior to tentacles at border of peristomium and setiger 1 ( Fig. 19B ); second pair of branchiae on posterior margin of setiger 1 dorsal to notosetae; branchiae on following segments in a similar position.

Notosetae of setigers 1–7(8) all long, thin capillaries, ca. 6–8 per fascicle; acicular hooks from setiger 8–9, 1–2 hooks at first accompanied by 2–3 thin capillaries, reduced to a single capillary in posterior segments or absent. Neurosetae of setigers 1–5 long capillaries, 5–8 setae per fascicle; bifid acicular hooks mostly replacing capillaries from setiger 6, continuing posteriorly; hooks accompanied by 1–2 thin, hair-like capillaries through middle body segments with these reduced to a single capillary in posterior setigers ( Fig. 19D ), or entirely absent. Hooks numbering 2–5 per fascicle, each with blunt, bifid tips. Posterior fascicles with noto- and neuropodial hooks curving toward lateral midline ( Fig. 19D ). Notopodial hooks thinner, longer than neuropodial hooks, with rounded or angular tips ( Fig. 19E ), a few with weakly bifid tips only in far posterior setigers. Neuropodial hooks with emergent end of shaft geniculate, sigmoidally curved, with tip bearing a blunt-tipped tooth on concave side of shaft and a narrow apical tooth on convex side of shaft as extension of sheath producing a bidentate appearance ( Fig. 19F ).

Methyl Green stain. No staining reaction.

Remarks. During the initial study of the Weddell Sea collections taken as part of the ANDEEP program, Blake & Narayanaswamy (2004) referred specimens of this species to the genus Tharyx . However, further study indicated that although all specimens were small and threadlike, two separate species were actually present: Caulleriella antarctica and Tharyx moniliformis n. sp. Caulleriella antarctica has typical bidentate neuropodial hooks in posterior parapodia; whereas, T. moniliformis n. sp. has the sub-bidentate knobby hooks typical for species of Tharyx . In addition, the pygidium of C. antarctica has two anal cirri; whereas, the pygidium of T. moniliformis n. sp. has only a simple lobe lacking cirri. Both species occur in the Weddell Sea, but T. moniliformis n. sp. occurs over a greater depth range.

Among species of Caulleriella occurring in deep-water sediments of Antarctica, C. antarctica , C. fimbriata n. sp., and C. kacyae n. sp. all have elongate, threadlike bodies. Caulleriella antarctica has two peristomial rings instead one or three, has the first pair of branchiae lateral to the dorsal tentacles on the peristomium instead of on setiger 1, and there is sheath on the convex side of the neuropodial hooks that extends as an apical tooth above the main fang. A similar sheath occurs in C. kacyae n. sp., but in that species, the sheath produces a pair of apical teeth.

Globally, C. antarctica with both straight and sigmoidally curved hooks in noto- and neuropodia is reminiscent of C. cordiformia described by Magalhães & Bailey-Brock (2013) from offshore Oahu, Hawaii. However, the types and distribution of these hooks in the Hawaiian species differ in that all are bidentate. Posterior elongate notopodial hooks alternate with capillaries and short curved neuropodial hooks alternate with long, narrow, straight bidentate hooks. In addition, while the first pair of branchiae of C. cordiformia occurs posteriorly on the peristomium as in C. antarctica , they occur directly posterior to the dorsal tentacles instead of lateral to them.

Habitat. Weddell Sea sample PS61/133-6 from the ANDEEP II survey was collected from surficial sediments having greenish grey silt-clay, with some sand and pebbles ( Diaz 2004; Howe et al. 2004).

Distribution. Weddell Sea, 400–1120 m; McMurdo Sound, 6 m.

Figures

FIGURE 19. Caulleriella antarctica Hartman, 1978. A, anterior end, left lateral view; B, anterior end, dorsal view; C, posterior end, dorsal view; D, posterior parapodium, left anterior view; E, posterior notopodial hooks; F, posterior neuropodial hooks. A–B, D–F, Holotype (USNM 46777); C, ANDEEP II, Sta. 133-6 (SMH 24907).