Caulleriella cryptica Blake 2022, new species

Caulleriella cryptica new species

Figures 1–2

urn:lsid:zoobank.org:act: D83CE795-FBD8-41D1-8242-8CA989E8A68A

Chaetozone sp. B: Maciolek et al. 1987b: D-2 (in part).

Material examined. (10 specimens) Off New England, North Atlantic ACSAR program, coll. G. Hampson, Chief Scientist. Sta. 5: Cruise NA-5, Rep. 3, 30 Apr 1986, 40°05.01′N, 67°29.90′W, 2085 m, holotype (USNM 1661368); Cruise NA-1, Rep. 2, 05 Nov 1984, 40°05.16′N, 67°30.01′W, 2070 m, 3 paratypes (USNM 1661369); Cruise NA-2, Rep. 2, 29 Apr 1985, 40°05.07′N, 67°29.78′W, 2065 m, 2 paratypes (USNM 1661370); Rep. 3, 29 Apr 1985, 40°05.07′N, 67°29.88′W, 2065 m, 1 paratype (USNM 1661371). Cruise NA-3, Rep. 2, 04 Jul 1985, 40°05.08′N, 67°29.85′W, 2060 m 3 paratypes USNM 1661372).

Description. A small threadlike species, holotype (USNM 1661368) complete, with 70 setigers, 13.6 mm long, 0.4 mm across anterior and middle segments, only narrowing in far posterior setigers (Fig. 2A); paratype (USNM 1661370) with 75 setigers, 7.1 mm long, 0.26 mm wide. Body generally cylindrical in cross section throughout, with segments of anterior third short, ca. 1.5 to 2 times as wide as long; middle and posterior setigers rounded, moniliform (Fig. 2A, E–F), slightly wider than long. Dorsal and ventral grooves absent. Color in alcohol light tan.

Pre-setiger region long, narrow, about as long as first five setigers (Figs. 1A, 2A–B, D); prostomium and peristomium merged with one another (Figs. 1A, 2D). Prostomium long, narrow, triangular, tapering to pointed tip (Figs. 1A, 2A–B, D); eyespots absent; nuchal organs narrow slits on posterior lateral margin, weakly pigmented. Peristomium smooth, merging seamlessly with setiger 1 (Fig. 1A); with partial division into two rings dorsally, not evident ventrally; dorsal tentacles arising from near anterior border of second ring, with first branchiae located lateral and posterior to tentacles (Fig. 1A); second pair of branchiae arising dorsal to notosetae on setiger 1; subsequent branchiae similarly located. Dorsal tentacles broken off; branchiae mostly missing, short, or as stubs.

Parapodia reduced to low ridges from which setae arise. Setae include capillaries and bidentate hooks. Notosetae all capillaries over most of body; capillaries long, usually numbering 8–10 per fascicle; notopodial bidentate hooks not present until setiger 50–60 (57 in holotype) with 1–2 long-shafted hooks and 4–5 capillaries. Neuropodia with 7–8 long capillaries at first with bidentate hooks from setiger 15–25 (15 in holotype); hooks short, curved, 1–2 at first then increasing to 3–4 per fascicle posteriorly. All hooks with conspicuous blunted main fang surmounted by short, pointed apical tooth; distinct hood present extending from main fang to shaft on concave side (Figs. 1B–D, 2C); hood requires 1000x magnification to discern clearly. Hooks of anterior neuropodia with main fang shorter, less conspicuous on some paratypes (e.g., USNM 1661371).

Pygidium with semi-circular disk extending below anal opening (Fig. 2F).

Methyl green staining. No pattern.

Remarks. The hooks of Caulleriella cryptica n. sp. are bidentate with a distinct transparent hood that extends from the main fang to the shaft on the concave side. The only other species of Caulleriella having such hooks is Caulleriella bathytata Blake, 2019 from the Clarion-Clipperton Zone in the abyssal Pacific Ocean. The two species are similar in size and number of setigers but differ in that the neuropodial hooks of C. cryptica n. sp. begin on setiger 15 instead of more posteriorly on setiger 31 and the prostomium of C. cryptica n. sp. is much longer and drawn out into a narrow triangular shape instead of being shorter, broadly triangular, and distinctly divided into two parts in C. bathytata. In addition, the peristomium of C. cryptica n. sp. is partially divided dorsally into two rings, whereas the peristomium of C. bathytata is entire.

Biology. All specimens are from North Atlantic ACSAR Station 5 on the lower continental slope off Georges Bank, adjacent to Lydonia Canyon at a depth of about 2070 m. Sediments consisted of about 66.5% sand and 33.5% silt + clay (Maciolek et al. 1987b). Caulleriella cryptica n. sp. was rare at this site, where 17 of the top 20 species were annelids. Of these, Aurospio dibranchiata Maciolek, 1981 was the most abundant species with 10.4% of the total fauna (Maciolek et al. 1987b). No specimens of C. cryptica n. sp. were observed with gametes.

Etymology. The epithet cryptica, is from the Greek, krypto, for hide or conceal, in reference to these specimens being hidden and misidentified as a species of Chaetozone.

Distribution. Off New England, 2060–2085 m.