Orbiniella tumida, Blake, 2020

Blake, James A., 2020, New species and records of deep-water Orbiniidae (Annelida, Polychaeta) from the Eastern Pacific continental slope, abyssal Pacific Ocean, and the South China Sea, Zootaxa 4730 (1), pp. 1-61 : 47-48

Orbiniella tumida new species

Figure 24

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Orbiniella sp. 1: Blake et al. 2009: 1797.

Material examined. Continental slope, off northern California, west of Farallon Islands, SF-DODS Benthic Monitoring Program, Sta. 23. 28 Sep 2017, 37°37.0012′N, 123°28.9813′ W, 2934 m, holotype ( LACM-AHF Poly 11662), 2 paratypes ( LACM-AHF Poly 11663) ; Sta. 10, 22 Sep 2002, 37°40.00′N, 123°31.00′, 2739 m, 1 paratype ( CASIZ 234025 ) ; Sta. 64, 26 Sep 2003, 37°35.98′N, 123°32.96′, 3130 m, 2 paratypes ( CASIZ 234032 ) ; Sta. 64, 29 Aug 2016, 3221 m, 37°36.0068′N, 123°32.9960′W, 3221 m, 1 paratype ( MCZ 153581 ) .— Northern California off Half Moon Bay, US EPA 102 Site Selection Survey, R / V Point Sur , coll. J.A. Blake, south of Pioneer Canyon , Sta. 4-15. 9 Sep 1991, 37°12.42′N, 123°15.81′W, 1730 m, 1 specimen ( CASIZ 234046 ) ; Pioneer Canon, Sta. C-7,19 Sep 1991, 37°17.57′N, 123°13.50′W, 1840 m, 1 specimen ( CASIZ 234052 ) .— Off Central California, abyssal Plain , Sta. M, coll. 15 Aug 2006, HOV Alvin Dive 4227, B. Strickrott (Pilot), 34°39.105′N, 123°05.116′W, 4119 m (1, JAB)

Description. A small species, holotype mostly complete but with damaged posterior end, 2.5 mm long, 0.8 mm wide with 21setigers; complete paratype (CASIZ 234032) 2.7 mm long, 0.36 mm wide, with 37 setigers; larger paratype (CZSIZ 234032) incomplete, 3.1 mm long, 0.25 mm wide, with 32 setigers. Body thick throughout, with no separate thorax and abdomen; all parapodia lateral, not shifted dorsally in posterior segments; individual segments crowded, about seven times wider than long ( Fig. 24A ). Each segment with narrow intersegmental swelling along most of body producing superficial bi-annulate appearance ( Fig. 24A ). Body with numerous subdermal glands appearing brown with Shirlastain A. Body somewhat dorsoventrally compressed, without dorsal or ventral longitudinal grooves. Holotype with eggs in setigers 7–11, each about 120–125 µm in diameter; individual eggs in notopodia forming large lobe, a possible brooding or discharge chamber. Color in alcohol: light tan.

Pre-setiger region short, narrower than following setigerous segments ( Fig. 24A ). Prostomium broadly rounded anteriorly; eyespots absent; nuchal organs prominent lateral lobes, with numerous long cilia ( Fig. 24A ). Peristomium with two narrow annular rings distinctly separated from one another dorsally and ventrally ( Fig. 24 A–B). First annular ring forming ventral lip of mouth; dorsal lip with broad opening or vestibule ( Fig. 24B ).

Branchiae entirely absent. Noto- and neuropodia formed as elongate lobes, more or less conical. Notopodia with short, clavate postsetal lamella ( Fig. 24D ). Notopodia with 1–2 large, acicular spines and 3–5 long camerated capillaries; neuropodia with one large acicular spine and 5–6 long capillaries; ( Fig. 24D ); furcate setae absent. Spines thick, smooth, tapering to narrow tip ( Fig. 24 E–H), some with a distinct notch where spine narrows abruptly ( Fig. 24 G–H). Capillaries all camerated with row of barbs along one edge.

Pygidium with four short anal cirri ( Fig. 24C ).

Methyl Green stain. Prostomium not staining; rest of body staining uniformly green, de-staining rapidly.

Remarks. Among deep-sea species of Orbiniella , O. tumida n. sp. is most similar to O. abyssalis n. sp. from the abyssal Pacific Ocean, O. andeepia from Antarctica, and O. petersenae from the NE Atlantic Ocean in having smooth acicular spines in noto- and neuropodia and a notopodial postsetal lamella (see previous Remarks for O. abyssalis n. sp.). In having a short, clavate notopodial postsetal lamella O. tumida n. sp. is most similar to O. abyssalis n. sp., but differs in having two distinct peristomial rings instead of one. Another distinguishing feature of O. tumida n. sp. is the presence of a notch on some acicular spines that has not been observed previously on orbiniids. Spines with notches occur in both noto- and neuropodia and occur randomly with spines lacking this feature.

Etymology. The epithet is from the Latin, tumidus for swollen, in reference to short, thickened body of this species.

Distribution. Off northern California, lower continental slope and abyssal plain, 1730–4119 m.

Figures

FIGURE 24. Orbiniella tumida n. sp. A, anterior end, dorsal view; B, anterior end, ventral view; C, posterior end, dorsal view; D, parapodium from mid-body setiger, anterior view; E–H, acicular spines. A–B, D–F, holotype (LACM-AHF Poly 11662); C, paratype (CASIZ 234032).