Anguillosyllis acsara, Maciolek, 2020

Maciolek, Nancy J., 2020, Anguillosyllis (Annelida: Syllidae) from multiple deep-water locations in the northern and southern hemispheres, Zootaxa 4793 (1), pp. 1-73 : 27-30

Anguillosyllis acsara n. sp.

Figures 7–8

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Material examined. Western North Atlantic continental slope and rise. (3 specimens in 3 samples from 2 stations). off North Carolina, U.S. South ACSAR Program, coll. J.A. Blake (Battelle), Chief Scientist. Sta. 3, Cruise SA 1, R/ V Columbus Iselin, 15 Nov 1983, Rep. 1, 34°14.13′N, 75°40.41′W, 1505 m, 1 juvenile (NJM). Cruise SA 2 , R/V Cape Hatteras , 27 March 1984, Rep. 1, 34°14.51′N, 75°40.33′W, 1523 m, holotype ( USNM 1480212 ). Sta. 12, Cruise SA 4, R/V Cape Hatteras , 22 May 1985, Rep. 1, 33°00.31′N, 76°07.39′W, 1996 m, paratype ( USNM 1480213 ) .

Description. Body with 11 setigers ( Fig. 8A ), holotype large, significantly arched dorsally, flat ventrally ( Fig. 7A, E ; 8 A–B); 2.5 mm long, 0.8 mm wide without parapodia, 1.2 mm wide with parapodia but without setae, other specimens much smaller, up to 1.5 mm long. Palps blunt-tipped, robust ovals, appear free to base on dorsal surface, connected by membrane on ventral surface. Prostomium wider than long, pentagonal; eyes lacking; three clubshaped antennae in nearly transverse row, lateral antennae slightly anterior to medial antenna. Peristomium with two oval tentacular cirri smaller than prostomial antennae; peristomium weakly biannulate, with glandular band across posterior half. Nuchal cilia in large oval patches between prostomium and peristomium.

Proventricle in three setigers, barrel-shaped, slightly narrowed at posterior end; ca. 15 muscle rows ( Figs. 7C ); post-ventricle caeca with dorsal circle of gland cells retaining MB stain ( Figs. 7C , 8 A–B).

Setigers dorsally biannulate, weakly so on setigers 1 and 5, obscured on setigers 6–10, visible on setiger 11 and pygidium ( Figs. 7 A–B, 8A–C); anterior annulation much shorter than posterior, posterior portion of each segment with gland cells scattered across dorsum ( Fig. 7A ), similar gland cells visible on setiger 11; additional area of dark gland cells at base of parapodia ( Fig. 7A ); venter biannulate on setigers 2–5. Parapodia uniramous, mitten-shaped, shortest on setiger 1, becoming longer, rectangular in subsequent setigers; with small, translucent anterior lobe on setigers 2–3 ( Fig. 7F ), lobe decreasing in size through setiger 6, then either smaller or absent through end of body; posterior lobe lacking on all setigers; dorsal lobe small, knobby, curled dorsally, clearest on setigers 1–5/6. Dorsal cirri retained on setiger 1, otherwise absent or lost; cirri thin, smooth, filiform. Ventral cirri thin, digitate, inserted midway on parapodia. Parapodia with smooth elongate internal glands, distal end narrowing and exiting through dorsal lobe ( Fig. 7F ).

All setae compound with heterogomph shafts, with short to long blades; setae emerging from distal end and ventral face of parapodium. Ventral falcigers with deeply serrated blade, bluntly rounded tip ( Fig. 7D ); spiniger-like blades clearly serrated at base, becoming plain near thin, fine tips; setiger 1 with ca. 30 falcigers ca. 70–90 µm long and 2–4 spiniger-like setae with long, fine tips up to 200 µm long; setigers 2–3 similar but with more spiniger-like setae; setigers 4–6 with ca. 50 setae, number of setae decreasing in setigers 7–11 to ca. 16–20; spiniger-like setae becoming more numerous and falcigers reduced in number posteriorly. Two aciculae per parapodium, both embedded or tip barely emergent, pointed ( Fig. 7F ); anterior acicula appearing bent in posterior setigers ( Fig. 7F ).

Pygidium biannulate, with two ventromedial filiform cirri, other cirri lost ( Figs. 7B , 8C ).

Reproductive features. Holotype with setigers 6–10 filled with possible gonadal products but individual eggs not detectable ( Fig. 8A ); juvenile specimen ca. 0.5 mm long, biannulation not evident.

Remarks. Anguillosyllis acsara n. sp. from North Carolina is similar to the widespread A. palpata and A. hampsoni n. sp. from shelf depths off New England in having 11 setigers and unfused palps, but differs in having a heavier habitus, smaller nuchal area, and falcigers with plain rather than hooked tips; more importantly, A. acsara n. sp. also lacks the posterior parapodial lobes of the other two species. Both A. acsara n. sp. and A. hadra n. sp. from the South China Sea have 11 setigers and bulky, dorsally arched bodies, and both lack posterior lobes on the parapodia; they differ in the larger size, clearer biannulation, smaller proventricle, more obvious nuchal patches, and greater number of setae in anterior setigers of A. acsara n. sp. compared with A. hadra n. sp. Anguillosyllis acsara n. sp. differs from almost all other Anguillosyllis in having numerous small glands covering the posterior half of the peristomium and first few setigers; only A. hadra n. sp. has similar dorsal glands on anterior segments.

Etymology. The species name is based on ACSAR, the acronym for the Atlantic Continental Slope and Rise program, during which this species was collected

Records. Off North Carolina, USA, 1505–1996 m .

Figures

FIGURE 7. Anguillosyllis acsara n. sp. Holotype (USNM 1480212): A, anterior end, dorsal view; B, posterior end, dorsal view; C, proventricle; D, tip of falciger; E, cross-section of body, not to scale. Paratype (USNM 1480213): F, setiger 3, dorsal view. Abbreviations: Acb—acicular bump, aL—anterior lobe, dL—dorsal lobe, dkGl—dark gland, ExGl—external gland, MGst—cells stained with Methyl Green, prov—proventricle, pVCa—post-ventricle caeca.

FIGURE 8. Anguillosyllis acsara n. sp. Holotype (USNM 1480212): A, entire specimen, dorsal view; B, anterior end, dorsal view; C, pygidium. A–B, with MG stain; C, with Shirlastain A.