Orbiniella acsara Blake 2021, new species

Orbiniella acsara new species

Figures 49–50

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Orbiniella sp. 1: Maciolek et al. 1987a: D-4; Maciolek et al. 1987b: D-3; Blake et al. 1987: C4; Hilbig 1994: 942.

Material examined (79 specimens). Off New England, U.S. North Atlantic ACSAR program, coll. G.W. Hampson, Chief Scientist. Sta. 14: Cruise N-1, Rep. 1, 09 Dec 1984, 39°40.90′N, 70°54.20′W, 2105 m, holotype (USNM 1622440) and 1 paratype (USNM 1622441); Cruise NA-2, Rep. 2, 05 May 1985, 39°40.93′N, 70°54.21′W, 2092 m, 1 paratype (USNM 1622442). Sta. 2: Cruise NA-1, Rep. 2, 08 Nov 1984, 40°57.20′N, 66°13.87′W, 2095 m, (2, USNM 1622443); Cruise NA-3, Rep. 2, 03 Jul 1985, 40°57.22′N, 66°13.73′W, 2100 m, 2 paratypes (USNM 1622444); Cruise NA-4, Rep. 1, 23 Nov 1985, 40°57.30′N, 66°13.75′W, 2114 m, 1, paratype (USNM 1622445); Cruise NA-6, Rep. 3, 25 Jul 1986, 40°57.23′N, 66°13.82′W, 2103 m, (1, USNM 1622446). Sta. 3: Cruise NA-6, Rep. 2, 08 Nov 1984, 41°01.03′N, 66°20.03′W, 1370 m, (1, USNM 1622447). Sta. 5: Cruise NA 4, Rep. 2, 25 Nov 1985, 40°05.09′N, 67°29.84′W, 2071 m (2, USNM 1622448); Rep. 3, 25 Nov 1985, 40°05.07′N, 67°29.81′W, 2071 m (3, USNM 1622449); Cruise NA 5, Rep. 1, 29 Apr 1986, 40°05.06′N, 67°29.94′W, 2052 m (1, USNM 1622450); Rep. 2, 29 Apr 1986, 40°05.07′N, 67°29.87′W, 2072 m (2, USNM 1622451); Rep. 3, 30 Apr 1986, 40°05.01′N, 67°29.90′W, 2085 m (1, USNM 1622452); Cruise NA-6, Rep. 1, 26 Jul 1986, 40°05.08′N, 67°29.79′W, 2063 m, 2 paratypes (USNM 1622453); Rep. 2, 26 Jul 1986, 40°05.03′N, 67°29.95′W, 2078 m (1, USNM 1622454). Sta. 6: Cruise NA-1, Rep. 3, 06 Nov 1984, 40°05.14′N, 67°29.35′W, 2112 m, 1 paratype (USNM 1622455); Cruise NA-2, Rep. 1, 29 Apr 1985, 40°05.03′N, 67°29.13′W, 2108 m, 1 paratype (USNM 1622456); Rep. 2, 29 Apr 1985, 40°05.06′N, 67°29.13′W, 2107 m (1, USNM 1622457); Cruise NA-5, Rep. 3, 01 May 1986, 40°05.10′N, 67°29.13′W, 2109 m, paratype (USNM 1622458); Cruise NA-6, Rep. 1, 26 Jul 1986, 40°05.07′N, 67°29.07′W, 2110 m, (1, USNM 1622459). Sta. 8: Cruise NA-5, Rep. 3, 29 Apr 1986, 40°10.14′N, 67°37.45′W, 2130 m, 1 paratype (USNM 1622460). Sta. 9: Cruise NA-1, Rep. 3, 12 Nov 1984, 39°50.53′N, 70°01.68′W, 1225 m (1, USNM 1622461). Sta. 10: Cruise NA-6, Rep. 1, 28 Jul 1986, 39°48.06′N, 70°05.26′W, 1226 m (1, USNM 1622462); Cruise NA-6, Rep. 3, 28 Jul 1986, 39°48.09′N, 70°05.25′W, 1228 m (1, USNM 1622463). Sta. 15: Cruise NA-2, Rep. 1, 05 May 1985, 39°40.08′N, 70°54.26′W, 2150 m, 1 paratype (USNM 1622464); Cruise NA-5, Rep. 2, 05 May 1986, 39°39.95′N, 70°54.19′W, 2164 m (1, USNM 1622465); Cruise NA-6, Rep. 1, 28 Jul 1986, 39°40.05′N, 70°28′W, 2153 m (2, USNM 1622466).— Off New Jersey and Delaware, U.S. Mid-Atlantic ACSAR program, coll. Rosemarie Petrecca, Chief Scientist. Sta. 1: Cruise Mid-2, Rep. 1, 03 Aug 1984, 38°36.12′N, 72°53.06′W, 2209 m (1, USNM 1622467). Sta. 2: Cruise Mid-3, Rep. 3, 02 Dec 1984, 38°35.68′N, 72°53.69′W, 2015 m (2, USNM 1622468); Cruise Mid-4, Rep. 1, 17 May 1985, 38°35.66′N, 72°53.81′W, 2010 m (1, USNM 1622469); Rep. 2, 17 May 1985, 38°35.66′N, 72°53.80′W, 2011 m (1, USNM 1622470); Cruise Mid-5, Rep. 3, 05 Aug 1985, 38°35.69′N, 72°53.78′W, 2005 m (1, USNM 1622471). Sta. 3: Cruise Mid-1, Rep. 3, 04 May 1984, 38°36.86′N, 72°51.29′W, 2060 m (2, USNM 1622472); Cruise Mid-4, Rep. 3, 16 May 1985, 38°36.75′N, 72°51.60′W, 2052 m (1, USNM 1622473); Cruise Mid-5, Rep. 3, 05 Aug 1985, 38°36.82′N, 72°51.54′W, 2050 m (1, USNM 1622474); Cruise Mid-6, Rep. 1, 12 Nov 1985, 38°36.73′N, 72°51.62′W, 2064 m (2, USNM 1622475). Sta. 5: Cruise Mid-1, Rep. 3, 08 May 1984, 38°50.46′N, 72°33.14′W, 2080 m (1, USNM 1622476); Cruise Mid-2, Rep. 3, 01 Aug 1984, 38°50.52′N, 72°32.96′W, 2074 m (1, USNM 1622477). Sta. 6: Cruise Mid-1, Rep. 1, 03 May 1984, 39°05.61′N, 72°02.98′W, 2090 m (1, USNM 1622478); Cruise Mid-3, Rep. 1, 28 Nov 1984, 39°05.58′N, 72°02.81′W, 2090 m (1, USNM 1622479); Rep. 2, 28 Nov 1984, 39°05.57′N, 72°02.83′W, 2090 m (2, USNM 1622480); Rep. 3, 28 Nov 1984, 39°05.58′N, 72°02.81′W, 2085 m (1, USNM 1622481); Cruise Mid-4, Rep. 1, 15 May 1985, 39°05.61′N, 72°03.26′W, 2090 m (1, USNM 1622482); Rep. 2, 15 May 1985, 39°05.66′N, 72°03.25′W, 2045 m (1, USNM 1622483); Cruise Mid-6, Rep. 1, 10 Nov 1985, 39°05.67′N, 72°03.36′W, 2089 m (3, USNM 1622484). Sta. 7: Cruise Mid-1, Rep. 2, 06 May 1984, 38°27.30′N, 73°03.43′W, 2100 m (1, USNM 1622485); Cruise Mid-2, Rep. 2, 03 Aug 1984, 38°27.32′N, 73°03.38′W, 2104 m (1, USNM 1622486); Cruise Mid-3, Rep. 3, 02 Dec 1984, 38°27.25′N, 73°03.44′W, 2110 m (1, USNM 1622487); Cruise Mid-5, Rep. 3, 07Aug 1985, 38°27.31′N, 73°03.54′W, 2088 m (1, USNM 1622488). Sta. 8: Cruise Mid-1, Rep. 1, 06 May 1984, 38°27.36′N, 73°05.09′W, 2150 m (1, USNM 1622489); Rep. 2, 06 May 1984, 38°27.36′N, 73°04.88′W, 2150 m (1, USNM 1622490). Sta. 9: Cruise Mid-1, Rep. 3, 06 May 1984, 38°17.23′N, 73°14.60′W, 2108 m (1, USNM 1622491); Cruise Mid-5, Rep. 3, 09 Aug 1985, 38°17.19′N, 73°14.63′W, 2100 m (1, USNM 1622492); Cruise Mid-6, Rep. 3, 17 Nov 1985, 38°17.23′N, 73°14.65′W, 2104 m (1, USNM 1622493). Sta. 10: Cruise Mid-4, Rep. 2, 19 May 1985, 37°51.75′N, 73°19.97′W, 2095 m (1, USNM 1622494); Cruise Mid-5, Rep. 1, 09 Aug 1985, 37°51.76′N, 73°20.04′W, 2095 m (2, USNM 1622495); Rep. 3, 09 Aug 1985, 37°51.75′N, 73°20.054′W, 2095 m (1, USNM 1622496). Sta. 12: Cruise Mid-1, Rep. 1, 07 May 1984, 38°29.34′N, 72°42.23′W, 2501 m (1, USNM 1622497); Rep. 3, 08 May 1984, 38°29.33′N, 72°42.24′W, 2500 m (1, USNM 1622498); Cruise Mid-5, Rep. 1, 07 Aug 1985, 38°29.23′N, 72°42.22′W, 2495 m (1, USNM 1622499). Sta. 13: Cruise Mid-3, Rep. 1, 30 Nov 1984, 37°53.32′N, 73°45.10′W, 1615 m (1, USNM 1622500); Cruise Mid-5, Rep. 1, 09 Aug 1985, 37°53.26′N, 73°45.21′W, 1607 m (3, USNM 1622501). Sta. 14: Cruise Mid-1, Rep. 3, 02 Apr 1984, 37°53.86′N, 73°44.68′W, 1503 m (1, USNM 1622502).— Southeastern USA, U.S. South Atlantic ACSAR program, coll. J.A. Blake, Chief Scientist. Off Cape Lookout, North Carolina, Sta. 4: Cruise SA-5, Rep. 1, 24 Sep 1985, 34°11.27′N, 75°38.63′W, 2032 m (1, USNM 1622503); Cruise SA-6, Rep. 2, 24 Nov 1985, 34°11.21′N, 75°38.61′W, 2049 m (1, USNM 1622504). Sta. 5: Cruise SA-3, Rep. 3, 12 Jul 1984, 34°05.60′N, 75°19.10′W, 3019 m (1, USNM 1622505). Off Cape Fear, North Carolina, Sta. 11: Cruise SA-4, Rep. 1, 22 May 1985, 33°04.86′N, 76°25.13′W, 800 m (1, USNM 1622506). Sta. 12: Cruise SA-4, Rep. 3, 22 May 1985, 33°00.20′N, 76°07.25′W, 2000 m (1, USNM 1622507); Cruise SA-5, Rep. 1, 22 Sep 1985, 33°00.36′N, 76°07.27′W, 2004 m (1, USNM 1622508). Off Charleston, South Carolina, Sta. 14: Cruise SA-6, Rep. 3, 18 Nov 1985, 32°23.70′N, 77°01.06′W, 799 m (1, USNM 1622509). Sta. 16: Cruise SA-5, Rep. 1, 14 Sep 1985, 31°35.19′N, 75°10.39′W, 3009 m (1, USNM 1622510).

Description. A long, narrow, threadlike species (Fig. 50A); holotype with 38 setigers, 4.78 mm long and 0.17 mm wide; paratype (USNM 1622444) with 43 setigers, 4.4 mm long, 0.19 mm wide. Body cylindrical in cross section throughout, with longitudinal grooves and ridges not apparent. Distinction between thoracic region and abdominal segments vague, mostly due to change in proportional size of anterior and middle segments with anterior 6–8 setigers short, about three times wider than long; middle segments longer, about 1.5 times longer than wide; segments again shorter in far posterior segments. Intersegmental areas narrow not enlarged (Fig. 49 A–B). Color distinctive, body light tan with dark particles concentrated into fecal pellets in gut providing characteristic dark internal patches along body in most specimens (Figs. 49B, 50 A–C). Close inspection of these pellets indicate multiple smaller particles comprising larger patches enclosed in membranes.

Pre-setiger region about as long as first 2½ setigers (Fig. 49 A–B). Prostomium triangular, tapering to narrow rounded tip (Figs. 49 A–B, 50A–B, D); eyespots absent; nuchal organs not observed. Peristomium with two narrow rings, weakly separated from one another (Fig. 49 A–B); ventrally forming anterior and posterior lips of mouth. Mouth a narrow slit with upper lip formed of about six short lobes; lower lip with lobes indistinct (Fig. 49B). Internal outline of pharynx visible dorsally (Figs. 49A, 50B), ventrally (49B) and laterally (Fig. 50D); no specimens observed with everted proboscis.

Parapodia lateral along entire body, not shifted dorsally (Fig. 49C); noto- and neuropodia close together, reduced to short rounded tori from which setae emerge, best seen in lateral view; in dorsal and ventral views, parapodia only projecting laterally in a few anterior setigers and newly formed posterior setigers (Fig. 50 A–C); postsetal lobes absent.

Noto- and neurosetae including long serrated capillaries on all segments, with 3–5 capillaries in notopodia and 2–4 capillaries in neuropodia. Long capillaries prominent along entire body (Fig. 50A). Noto- and neuropodia also with 1–2 short curved acicular spines, directed towards one another, vis-à-vis (Fig. 49C).

Pygidium simple, rounded, bi-lobed, surrounding anal opening; anal cirri absent (Fig. 50A, C, F).

Remarks. Among the ten deep-water species of Orbiniella compared by Blake (2020), O. acsara n. sp. with smooth acicular spines and no postsetal lobes is most similar to O. aciculata Blake, 1985 from the Galápagos Rift hydrothermal vents and O. eugeneruffi Blake, 2020 from off Brunei in the South China Sea. Orbiniella acsara n. sp. differs from these species in having both peristomial rings large, of an equivalent size, and incomplete instead of one or both rings being narrow and complete. In addition, O. acsara n. sp. has no anal cirri on the pygidium instead of two or four anal cirri.

Orbiniella acsara n. sp. is also unusual in having a long, narrow, threadlike body with long capillary noto- and neurosetae. Most species of the genus have shorter, more compact bodies where the individual segments are often separated by thickened intersegmental areas producing a biannulate appearance. With O. acsara n. sp., the intersegmental areas are irregular and not formed into well-defined rings between the parapodia. In addition, the dark fecal pellets that occur in the intestine of nearly all specimens assist with recognition.

Biology. Eggs were observed in a few specimens. An ovigerous specimen (USNM 1622502) was packed with eggs along most of the body, with smaller eggs in anterior segments and larger ones in mid-body segments (Fig. 50E). The largest eggs in this specimen were 83 x 107 µm and 83 x 116 µm; this would equate to an average width of ca. 95–100 µm; each visible egg was observed to have a smooth cytoplasm and a distinct germinal vesicle.

The groups of dark fecal pellets in the intestine of most specimens were observed to consist of silt particles confined by a thin membrane consistent with fecal pellet formation. Orbiniella acsara n. sp. is primarily a lower slope species (1500–3000 m) and as such occurs in sediments having a high silt + clay content (Blake et al. 1987; Blake & Grassle 1994; Maciolek et al. 1987a–b). Owing to its small size and threadlike body, it is likely that the species resides in the upper 1–2 cm where it has access to and feeds at the sediment-water interface where newly deposited fine-grained flocculent sediments occur.

Etymology. The name acsara is derived from the acronym, ACSAR, for the Atlantic Continental Slope and Rise program (1983–1987); the new species was collected from all three survey regions.

Distribution. U.S. Atlantic continental slope: off New England, 1225–2164 m; off Delaware and New Jersey, 1503–2500 m; off North and South Carolina, 799–3019 m.