Anguillosyllis hadra, 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 : 35-38

Anguillosyllis hadra n. sp.

Figures 12–13

urn:lsid:zoobank.org:act:9C19C021-CE55-4A8D-83FC-3BB10AC72512

Material examined. (14 specimens from 9 samples). South China Sea, off Brunei. Coll. J. A. Blake, Chief Scientist. Sta. 35, 3 Jun 2011, 5°47′37.12906″N, 114°14′10.75153″E, 1329 m, paratype ( MCZ 148520 ) ; Sta. 44, 2 Jun 2011, 5°47′22.97393″N, 114°15′36.22932″E, 1294 m, 1 specimen ( MCZ 148521 ) ; Sta. 46, 2 Jun 2011, 5°48′02.68476″N, 114°18′10.00693″E, 1234 m, holotype ( MCZ 148522 ) ; Sta. 47, 2 Jun 2011, 5°47′21.86444″N, 114°17′10.72194″E, 1242 m, 3 specimens ( MCZ 148523 ) ; Sta. 48, 2 Jun 2011, 5°45′28.93802″N, 114°15′23.44165″E, 1219 m, 1 spec- imen ( MCZ 148524 ) ; Sta. 49, 2 Jun 2011, 5°44′24.32540″N, 114°13′59.60803″E, 1199 m, 2 specimens ( MCZ 148543 ) ; Sta. 58, 1 Jun 2011, 5°44′45.95938″N, 114°17′28.05056″E, 1127 m, 1 specimen ( MCZ 148544 ) ; Sta. 61, 31 May 11, 5°40′32.90422″N, 114°13′15.64893″E, 1050 m, 1 specimen ( MCZ 148545 ) ; Sta. WH Jagus E Subthrust, 1 Jun 2011, 5°46′34.64026″N, 114°17′24.73418″E, 1214 m, 3 specimens ( MCZ 148546 ) .

Description. Body with 11 setigers ( Fig. 12A ), bulky, opaque, arched dorsally; up to 1.5 mm long, 0.4 mm wide without parapodia, 0.6 mm wide with parapodia but without setae. Palps slim, bean-shaped ovals, appear free to base on dorsal surface, connected by membrane on ventral surface. Prostomium wider than long; eyes lacking; three club-shaped antennae in nearly transverse row. Peristomium with two tentacular cirri smaller than prostomial antennae; peristomium not clearly demarcated from prostomium, together appearing nearly square. Nuchal cilia present between prostomium and peristomium, but not obvious. Proventricle in 4–4.5 setigers, barrel-shaped, only slightly narrowed at posterior end ( Fig. 12A ); ca. 24 muscle rows not clearly defined; post-ventricle caeca with dorsal gland cells lacking or not retaining MB stain.

Dorsum biannulate through first four setigers, posterior annulation with small dorsal glands that retain MB stain ( Fig. 12A ). Parapodia uniramous, short, rectangular, length equal to about half or less body width (may appear short in dorsal view because of bulkiness of arched dorsum); with small, translucent anterior lobe increasing slightly in size through setiger 5 then decreasing through end of body ( Figs. 12 B–D, 13B); posterior lobe lacking; dorsal lobe small, sometimes curled dorsally, clearest on setigers 1–5/6. Dorsal cirri retained on setiger 1, otherwise absent or lost; cirri thin, smooth, filiform. Ventral cirri with wider base tapering to narrower tip, inserted midway on parapodia. Parapodia with smooth elongate internal glands, one end associated with cluster of tightly packed pentagonal cells, distal end of tube narrowing and exiting through dorsal lobe or surface of parapodium, rarely retaining faint MB stain ( Figs. 12 C–E, 13A–D).

All setae compound with heterogomph shafts, with shorter falcigers and longer spiniger-like blades; falcigers with deeply serrated, blunt-tipped blade; spiniger-like blades clearly serrated at base, becoming plain near thin, fine tips; setae numbering 20–22 in setigers 1–4; 12–14 in setigers 5–8, 10– 12 in setigers 9–11; setae emerging from distal end and ventral face of parapodium. Two or three stout pointed embedded aciculae per parapodium, posterior acicula with distal end bent (MCZ 148520), others straight and pointed.

Pygidium with four cirri: two, large, inflated lateral cirri and two filiform ventromedial cirri ( Fig. 12A ).

Reproductive features. None of the specimens had eggs, but one sample included a very tiny specimen (<0.5 mm) with 10 setigers that could be a juvenile of this species.

Glands. The specimen from Sta. 35 (MCZ 148520) differed from the other specimens in having clear, elongated, internal glands on the dorsum as well as at the distal end of the parapodia ( Figs. 12E , 13A, E ). The glands on the dorsum started on setiger 4 at the base of the parapodia and on subsequent setigers became more numerous and higher on the dorsal surface, extending to near the midline. These clear structures were connected at one end to rosettes or clusters packed with small cells that appeared pentagonal or octagonal; these rosettes most likely surround the external opening of the tubular gland, but thin sections and histological staining are necessary to clarify the structure of these glands. Neither the long tubes nor the clusters of small cells retained any MB stain.

Remarks. Anguillosyllis hadra n. sp. is most similar to A. aciculata n. sp., also from the South China Sea, and to A. acsara n. sp. from off North Carolina: all three species have 11 setigers, palps that are free or mostly free to the base, and significant numbers of glands both in the parapodia and on the dorsum; all three species lack posterior lobes on the parapodia. Anguillosyllis hadra n. sp. differs most noticeably from A. aciculata n. sp. by lacking the emergent acicula that characterize the latter species and from A. acsara n. sp. by a different arrangement of dorsal glands, smaller proventricle, less obvious nuchal patches and dorsal biannulation, and fewer setae in anterior setigers.

Considering other species from the east coast of North America, Anguillosyllis hadra n. sp. differs from A. palpata in lacking a posterior lobe on the parapodia, in having greatly enlarged lateral anal cirri, and having structurally complex parapodial glands, rather than having a large posterior lobe, small flattened lateral cirri, and a few simple internal glands; it also has a barrel-shaped proventricle compared to the cordate proventricle of A. palpata . Anguillosyllis hadra n. sp. differs from A. hampsoni n. sp. in having fewer very short falcigerous setae in the first few setigers as well as in the characters described for A. palpata .

Etymology. The specific epithet is an adjective taken from the Greek hadros, meaning well-developed or bulky; it refers to the broad bulky body of this species.

Records. South China Sea, off Brunei; 1015–1329 m.

Figures

FIGURE 12. Anguillosyllis hadra n. sp. Holotype (MCZ 148522): A, entire specimen, dorsal view; B, setigers 1–2; C, setiger 3; D, setiger 6. Paratype (MCZ 148520): E, setiger 5, inset not to scale. Abbreviations: ac—anal cirri, Acb—acicular bump, aL—anterior lobe, dL—dorsal lobe, ExGl—external gland, InGl—internal gland, SeSac—setal sac.

FIGURE 13. Anguillosyllis hadra n. sp. Paratype (MCZ 148520):A, setigers 4–7; B, setigers 4–5; C, parapodial glands, setiger 5; D, parapodial gland, setiger 5; E, dorsal glands, setiger 5.