Anguillosyllis truebloodi, 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 : 44-46

Anguillosyllis truebloodi n. sp.

Figures 18–19

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Material examined. Abyssal Pacific Ocean, Clarion-Clipperton Fracture Zone . (8 specimens from 4 samples, 3 stations) Coll. Dwight D. Trueblood for NOAA. Sta. 4-93 , 11 August 1993, 12 o 55.595′N, 128 o 35.943′W, 4861 m, 2 paratypes ( USNM 1480275 ) . Sta. 12-93 , 4 Sep 1993, 12 o 56.329′N, 128 o 35.698ʹW, 4851 m, 1 specimen ( NJM) . Sta. 1-94 , 25 July 1994, 12 o 55.788′N, 128 o 35.843′W, 4851 m, holotype ( USNM 1480273 ) and 2 paratypes ( USNM 1480274 ) . NOAA DOMES Site C , coll. R.R. Hessler, ECHO I, sample H351, nodule wash, Sandia box corer, 14 June 1983, 14 o 37.63ʹN, 125 o 26.38ʹW, 4516 m, 1 specimen ( LACM-AHF Poly 10168 )

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Description. Body with 11 setigers ( Fig. 18A ); holotype measuring 1.2 mm long, 0.25 mm wide without parapodia, 0.6 mm wide with parapodia but without setae; other specimens less than 1.0 mm. Palps short, fused halfway to base, median furrow to base visible under high magnification, tips rounded, free and slightly divergent. Prostomium wider than long, oval, almost rectangular; eyes lacking; three club-shaped antennae in transverse row, lateral antennae slightly anterior to medial antenna. Peristomium with two tentacular cirri, smaller than prostomial antennae; peristomium not clearly visible on some specimens; nuchal cilia may be present between prostomium and peristomium but not obvious. Eversible pharynx with distal ring of 10 soft papillae. Proventricle in 2–3 setigers, barrel-shaped, anterior margin straight, posterior end slightly tapered ( Fig. 18A ); muscle rows not clearly apparent; post-ventricle caeca with dorsal gland cells lacking or not retaining MB stain.

Parapodia uniramous, elongated, rectangular, length equal to or greater than body width ( Fig. 18A ); small anterior lobe increasing in size through setiger 5 then decreasing through end of body; small posterior lobe from setiger 2, becoming increasingly larger through setiger 7, remaining large through last several setigers; dorsal lobe increasing in size through setiger 5 or 6, thereafter decreasing in size, usually curled dorsally ( Fig. 18B , D–E). Parapodia from setiger 4 to end of body with increasing number of oval to round glands concentrated near distal tips and in dorsal parapodial lobes ( Figs. 18 D–E, 19A–C), glands retaining MB stain. Dorsal cirri mostly lost, those present thin, smooth, filiform; basal cirrophores visible on all setigers, including setiger 2. Ventral cirri inserted on distal half to quarter of parapodia, with wider base tapering to narrower tip.

All setae compound with long heterogomph shafts, with short to very long blades; falcigers with serrated blades 20–50 µm long, tip slightly hooked ( Fig. 18C ), spiniger-like blades up to 200 µm, clearly serrated at base, becoming very fine near plain tips. Largest specimen with 20–22 setae per parapodium, most emerging from distal end and a few emerging from ventral face of parapodium. Two stout, pointed aciculae per parapodium, seen most clearly starting from setiger 6.

Pygidium damaged on all specimens, but with at least one short filiform ventromedial cirrus, additional cirri likely lost.

Remarks. Anguillosyllis truebloodi n. sp. is similar to A. capensis in having dorsal cirri (or indications of those cirri) on setiger 2 and posterior parapodial lobes; the two species differ in their overall size, with A. capensis reported to be up to 3.5 mm long and A. truebloodi n. sp. only one-third that size, and in the length and degree of fusion of the palps, which are longer and fused for more of their length in A. capensis compared with shorter and fused only halfway in A. truebloodi n. sp. Anguillosyllis truebloodi n. sp. is also similar to A. denaria n. sp. in the shape and degree of fusion of the palps: in both species, the palps are fused both dorsally and ventrally for at least half their length. However, A. truebloodi n. sp. has 11 setigers whereas A. denaria n. sp. has 10 setigers. A. truebloodi n. sp. also differs from the remaining 11-setiger species in the degree of fusion of the palps, with those of A. aciculata n. sp., A. acsara n. sp., A. hadra n. sp., A. hampsoni n. sp., and A. palpata appearing free dorsally although possibly fused ventrally, and in having a large number of round walnut-shaped glands rather than elongated glands concentrated in the dorsal and posterior lobes of the parapodia. Recovered from the CCFZ, Anguillosyllis truebloodi n. sp. is the deepest-occurring species examined in the study, overlapping with A. palpata , A. hessleri n. sp., and additional species that cannot be fully described due to the poor nature of the material.

With the exception of the holotype, the material is in very poor condition; while the anterior (head) region on all specimens allowed confirmation of the structures seen on the holotype, the remaining segments were somewhat decomposed.

Etymology. This species is named for Dr. Dwight D. Trueblood, who collected the majority of the specimens and made them available for study.

Records. Abyssal Pacific, 4516–4861 m.

Figures

FIGURE 18. Anguillosyllis truebloodi n. sp. Holotype (USNM 1480273): A, entire specimen, dorsal view; B, setiger 1, dorsal view; C, falcigers, inset not to scale; D, setiger 8, dorsal view; E, setigers 9–11, dorsal view. Abbreviations: Acb—acicular bump, aL—anterior lobe, dL—dorsal lobe, InGl—internal gland, pL—posterior lobe, vC—ventral cirrus.

FIGURE 19. Anguillosyllis truebloodi n. sp. Holotype (USNM 1480273): A, setiger 8, glands in posterior lobe; B, setiger 8, gland in dorsal lobe; C, close up of glands. Stained with Shirlastain A. Abbreviations: dL—dorsal lobe, gl—gland, pL—posterior lobe.