Caulleriella kacyae Blake 2018, new species

Caulleriella kacyae new species

Figure 25

Material examined. Weddell Sea, off Cape Norvegia, R / V Polarstern, ANDEEP III (ANT-XXII/3), Sta. 67/74-5, 20 Feb 2005, 71°18.11ʹS, 13°56.33ʹW, MUC, 1035 m, holotype (SMF 24909).

Description. A moderate-sized species, holotype complete, but fragile, broken into five pieces, totaling 10.7 mm long and up to 0.4 mm wide across middle segments; with about 135 setigerous segments. Body elongate, consistent in width throughout. A deep mid-ventral groove present from setiger 1 to end of body (Fig. 25B); first few anterior segments also with distinct ridge arising from floor of groove. Dorsum smooth, elevated above notopodia, without longitudinal groove or ridge (Fig. 25A). Noto- and neuropodia widely separated from each other with neuropodia located on each side of ventral groove (Fig. 25 A–B). All segments short, about nine times wider than long. Color in alcohol light tan with no separate body pigment.

Prostomium narrow, conical tapering to rounded apex (Fig. 25A); eyespots absent; nuchal organs oval, located at posterior lateral margins. Peristomium with three separate rings best seen laterally (Fig. 25A), dorsally elevated with rounded crest; dorsal tentacles widely spaced, arising from posterior end of last ring (Fig. 25A). First pair of branchiae on setiger 1 dorsal to notosetae; subsequent branchiae from same location; branchiae continuing segmentally to near posterior end.

All segments with notopodia dorsally elevated as shoulders above smooth, broad dorsum (Fig. 25A). Parapodia reduced to simple mounds from which setae arise. Notosetae include 8–10 simple capillaries on the first 60–70 setigers, fewer capillaries posteriorly; capillaries joined by 1–2 simple acicular spines from about setiger 105. Anterior neuropodia with 7–8 capillaries; 1–2 acicular spines first present from setiger 18, continuing to posterior end, increasing to six spines in posterior half of body entirely replacing capillaries (Fig. 25C). Notopodial spines thin, relatively straight, with simple blunt tips. Neuroacicular spines short, curving to narrow, blunt-tipped main fang or tooth; this tooth surmounted by sheath split medially forming two sharply pointed teeth (Fig. 25 E–F), these appearing as a single tooth in certain lateral views (Fig. 25D).

Pygidium with anus surrounded dorsally by five rounded papillae and ventrally by broad cushion with two long lateral cirri (Fig. 25B).

Methyl Green stain. No stain retained.

Etymology. This species is named in memory of my beautiful little cat Kacy, whose companionship over many years is greatly missed.

Remarks. Caulleriella kacyae n. sp. is unusual in the genus by having neuropodial acicular spines with two side-by-side apical teeth suggesting a tridentate structure. However, careful observation at 1500x suggests that the apical structure is likely a broad sheath that is divided into two parts. The true nature of the teeth on the hooks, however, is beyond the resolution of light microscopy. Given that only a single specimen is available, SEM observations will have to await the collection of additional specimens. The notopodial acicular spines are slender, straight, and do not appear to have any accessory teeth.

Caulleriella kacyae n. sp. and two other similar-appearing threadlike species of Caulleriella, C. antarctica and C. fimbriata n. sp., occur in Antarctic deep-sea sediments. Caulleriella kacyae n. sp. differs from the other two species in having three peristomial rings instead of two or one, respectively, in having the noto- and neuropodial hooks first present from setigers 105 in notopodia and setiger 18 in neuropodia instead of setigers 8–9 or 23 in notopodia and setiger 6 in neuropodia, and in having the bidentate hooks with a unique apical sheath or hood that appears to be divided into two parts instead of a single apical tooth. Details separating these three species and others from C. kacyae n. sp. are listed in Table 2 in the Discussion.

Habitat. Surficial sediments collected as part of the ANDEEP III survey at a site near the type-locality of Caulleriella kacyae n. sp. in the Weddell sea off Cape Norvegia consisted of poorly sorted olive grey sandy mud with sand (9%), silt (72%), and clay (19%) (Howe et al. 2007).

Distribution. Southern Weddell Sea, 1035 m.