Scoloplos pettiboneae Blake 2021, new species

Scoloplos pettiboneae new species

Figures 18–20

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Scoloplos acmeceps: Maciolek-Blake et al. 1985: B-5; Blake et al. 1998: C-1, C-2. Not Chamberlin 1919a.

Material examined. (132 specimens) Northeastern USA, Georges Bank, Benthic Infauna Monitoring Program (1981–1985), coll. G.W. Hampson, Chief Scientist. Sta. 5-11: Cruise M 3, R/V Endeavor, Rep. 1, 16 Feb 1982, 40°39.2′N, 67°46.6′W, 81 m, holotype (USNM 1621020). Sta. 5- 1: Cruise M-14, R/ V Gyre, Rep. 4, 26 Nov 1985, 40°39.44′N, 67°46.03′, 76 m (1 juvenile, USNM 1622338). Sta. 5-3: Cruise M 4, R/ V Cape Henlopen, Rep. 1, 14 May 1982, 40°39.8′N, 67°46.1′W, 84 m, 1 paratype (USNM 1621021). Sta. 5-4: Cruise M 4, R/ V Cape Henlopen, Rep. 4, 14 May 1982, 40°39.5′N, 67°46.5′W, 80 m (4, USNM 1621022). Sta. 5-5: Cruise M 2, R/V Oceanus, Rep. 4, 19 Nov 1981, 40°39.3′N, 67°46.2′W, 81 m, 1 paratype (USNM 1621023); Cruise M6, R/V Oceanus, Rep. 3, 23 Nov 1982, 40°39.3′N, 67°46.2′W, 79 m, 2 paratypes (USNM 1621024). Sta. 5-18: Cruise M 2, R/V Oceanus, Rep. 4, 18 Nov 1981, 40°39.6′N, 67°47.6′W, 80 m, 1 paratype (USNM 1621025); Cruise M 3, R/ V Endeavor, Rep. 6, 15 Feb 1982, 40°39.6′N, 67°47.6′W, 82 m (11, USNM 1621026). Sta. 5-29: Cruise M 3, R/ V Endeavor, Rep. 1, 15 Feb 1982, 40°39.5′N, 67°50.4′W, 85 m (1, USNM 1621027); Cruse M 4, R/ V Cape Henlopen, Rep. 5, 24 Nov 1982, 40°39.5′N, 67°50.4′W, 83 m, 1 paratype (USNM 1621028). Sta. 5-25: Cruise M 1, R/ V Eastward, Rep. 6, Jul 1981, 40°39.4′N, 67°46.9′W, 80 m (3, USNM 1621029); Cruise M 4, R/ V Cape Henlopen, Rep. 5, 19 May 1982, 40°39.5′N, 67°49.0′W, 82 m (4, USNM 1621030). Sta. 3: Cruise M 3, R/ V Endeavor, Rep. 3, 18 Feb 1982, 66°53.7′N, 66°46.5′W, 97 m, 8 paratypes (USNM 1621031); Cruise M 4, R/ V Cape Henlopen, Rep. 1, 12 May 1982, 40°53.7′N, 66°46.5′W, 90 m (7, USNM 1621032); Rep. 3, 4 paratypes (USNM 1621033); Cruise M5, R/V Oceanus, Rep. 1, 24 Jul 1982, 40°34.3′N, 67°45.3′W, 92 m, 8 paratypes USNM 1621034); Rep. 3 (14, USNM 1621035); Cruise M 6, Rep. 3, 22 Nov 1982, 40°34.3′N, 67°45.3′W, 98 m, 10 paratypes (USNM 1621036); Rep. 5, 10 paratypes (USNM 1621037). Sta. 6: Cruise M 6, R/V Oceanus, Rep. 1, 22 Nov 1982, 40°34.3′N, 67°45.3′W, 98 m (3, USNM 1621038). Sta. 12: Cruise M 2, R/V Oceanus, Rep. 4, 12 Nov 1981, 40°22.2′N, 68°30.2′W, 105 m (5, USNM 1621039). Sta. 13: Cruise M 5, R/V Oceanus, Rep. 5, 28 Jul 1982, 40°29.5′N, 70°12.6′W, 62 m (5, USNM 1621040). Sta. 18: Cruise M 2, R/V Oceanus, Rep. 3, 18 Nov 1981, 40°33.5′N, 67°13.7′W, 150 m, 8 paratypes (USNM 1621041).— Massachusetts Bay, MWRA Harbor and Outfall Monitoring Program. 1992 August Survey: Sta. NF-17, 42°22.88′N, 70°48.89′W, 29 m (10, MCZ 161599). 1996 August Survey: Sta. NF-19, 42°22.30′N, 70°48.30′W, 32 m (7, MCZ 161600). Sta. NF-24, Rep. 1, 42°22.83′N, 70°48.10′W, 37 m (1, MCZ 161601). Sta. MF-4, 42°24.93′N, 70°48.39′W, 36 m (1, MCZ 161602). Sta. MF-7, 42°24.60′N, 70°48.89′W, 33 m (1, MCZ 161603). Sta. MF-8, 42°24.00′N, 70°51.81′W, 30 m (5, MCZ 161604). Sta. MF-9, 42°23.99′N, 70°50.69′W, 29 m (2, MCZ 161605). Sta. MF-20, 42°22.69′N, 70°50.69′W, 28 m (1, MCZ 161606). Sta. FF-1A, Rep. 2, 42°33.84′N, 70°40.55′W, 32 m (1, MCZ 161607). Sta. FF-9, Rep. 2, 42°18.75′N, 70°39.40′W, 49 m (2, MCZ 161608). 1997 August Survey: Sta. MF-12, Rep. 3, 42°23.40′N, 70°49.83′W, 34 m (1, MCZ 161609). Sta. FF-9, Rep. 2, 42°18.75′N, 70°39.40′W, 49 m (1, MCZ 161610); Rep. 3 (1, MCZ 616611). Sta. FF-12, Rep. 2, 42°23.40′N, 70°53.98′W, 22 m (1, MCZ 161612).

Comparative material examined. California, Tomales Bay, Pelican Point, coll. 15 Aug 1952, Pacific Marine Station, intertidal, 4 specimens of Scoloplos acmeceps Chamberlin, 1919a (JAB).

Description. A moderate to large species; thorax broad, with segments about five times wider than long; generally flattened across both dorsal and ventral surfaces; abdominal segments ventrally rounded, dorsally flattened, with elevated parapodia; middle and posterior segments numerous, short, and crowded. Shallow ventral groove present on few thoracic segments or absent; dorsal longitudinal grooves and ridges absent. Holotype complete, with 115 setigers, 30.1 mm long, 0.8 mm wide across thorax; with 17 thoracic segments and branchiae from setiger 14. Paratype (USNM 1621037) with 102 setigers, 20 mm long, 0.7 mm across 17-setiger thorax; branchiae from setiger 13. Color in alcohol light tan. Middle thoracic setigers and a few anterior abdominal setigers with transverse band of glands across middle of dorsal and ventral surfaces of individual segments (Figs. 18A, 19 A–B); these glands retaining pink color of Rose Bengal applied during the benthic sorting process and staining darkly with Shirlastain A. Subpodial flanges of abdominal segments also stain prominently due to dense concentrations of internal glands (Figs. 18 E–F; 19C).

Pre-setiger region elongate, triangular, about as long as first three setigers (Figs. 18 A–C, 19A). Prostomium long, narrowing to acutely pointed apex (Fig. 18 A–C); nuchal organs elongate grooves on posterior lateral margins (Fig. 18C); eyespots absent. Peristomium a single ring, shorter than first setiger, smooth on dorsal surface, ventrally with a row of short lobes forming the posterior lip of mouth; dorsal lip a smooth surface without lobes (Fig. 18 B–C); proboscis rarely everted, one paratype (USNM 161682) with proboscis with three thick rounded lobes.

Thoracic notopodia triangular, short at first, with postsetal lobe becoming longer in posterior thoracic segments (Fig. 18D); each notopodial lobe arising from a thick base. Thoracic neuropodia fleshy, enlarged and rounded, with short nipple-like postsetal lobe (Fig. 18 D–E); subpodial papillae absent. Transition from thorax to abdomen generally abrupt due to appearance of elongated neuropodium with fewer setae and development of two unequal apical neuropodial lobes (Fig. 18E). Interramal cirri absent, but short interramal process or protuberance present between noto- and neuropodia of abdominal segments (Fig. 18E). Last one or two thoracic neuropodia with a subpodial lamella that transitions into prominent subpodial flange of abdominal segments.

Branchiae from posterior thoracic setiger, usually setiger 13 or 14 in larger specimens (Fig. 18A); branchiae narrow, short at first, becoming longer but still narrow, with rounded apex through middle abdominal segments (Fig. 18E); branchiae of posterior segments also narrow, but tapering to somewhat pointed apex (Fig. 18F); all branchiae heavily ciliated on medial and lateral margins (Fig. 18 E–F).

Thoracic notosetae numerous thick, long, camerated capillaries arranged in 3–4 rows. Thoracic neurosetae arranged in up to five rows with first three rows consisting of numerous short uncini and posterior rows of camerated capillaries (Fig. 18D). Individual uncini with shafts tapering to rounded tip; concave side of shaft with rows of barbs (Figs. 18 G–I, 19D–E); convex side of shaft with narrow thickened hood on some uncini (Figs. 18 G–H, 19E); this hood prominent on some setae. Abdominal notosetae thin, camerated capillaries and 1–2 furcate setae. Furcate setae with unequal tynes; each tyne with blunted tip and apical notch, with row of thin needles extending medially (Figs. 18J, 19F). Abdominal neurosetae with up to 4–5 thin capillaries each with short barbs along one edge and 1–2 curved aciculae, sometimes protruding, with rounded tip. Flail setae not observed.

Pygidium short, with two rounded dorsal lobes, two large lateral lobes and a single large ventral lobe surrounding anal opening; with two long, thin anal cirri arising dorsally (Fig. 19G).

Juvenile morphology. Juveniles of this species were initially thought to belong to the genus Schroederella, originally established for small interstitial or meiofaunal orbiniids found in intertidal sand beaches (Laubier 1962, 1971; Badalamenti & Castelli 1991, but see above for L. acutus). However, several of the distinctive characters of Scoloplos pettiboneae n. sp. were found on these juveniles, thus establishing their identity as this species. Study of the juveniles allowed some aspects of juvenile morphology to be documented; however, a complete growth sequence was not established. A specimen from Georges Bank (USNM 1622338) was examined in detail and is described here.

Specimen long, narrow, threadlike, complete with 41 setigers, 5.5 mm long, 0.25 mm wide across thoracic region (Fig. 20A). Color light tan, with distinct glandular bands present dorsally on anterior setigers (Fig. 20A).

Prostomium long, triangular, acutely pointed (Fig. 20 A–B); eyespots absent; nuchal organs not observed. Peristomium with two achaetous rings, not well separated from one another (Fig. 20 A–B); anterior dorsal border with prostomium weakly sculpted; ventrally obscured by upper lip of mouth. Upper lip of mouth with two large lobes; lower lip with broad border, lobes not well developed at this stage (Fig. 20B).

Thorax with nine setigers, slightly wider than abdominal segments through setiger 7, then narrowing, entire body thin and fragile throughout. Branchiae from setiger 10, narrow, arising near base of notopodia. Thoracic setigers short, about three times wider than long (Fig. 20 A–B); abdominal segments becoming long, narrow (Fig. 20C), then short again in far posterior setigers.

Thoracic notopodia initially short, papillate, increasing in length and becoming digitiform by about setiger 4–5; abdominal notopodia long and narrow. Thoracic neuropodia similar to notopodia; abdominal neuropodia with thickened base with two apical lobes, ventral lobe longer, narrower than dorsal lobe (Fig. 20D). Neuropodia with short, glandular subpodial flange (Fig. 20D). Subpodial papillae absent. Interramal processes not evident at this stage, but some parapodia with rounded folds between abdominal noto- and neuropodia.

Thoracic notosetae 4–6 camerated capillaries; abdominal notosetae 3–4 camerated capillaries and one furcate seta. Thoracic neurosetae consisting of two rows of 3–4 uncini and 6–10 long, camerated capillaries. Uncini with 3–4 short ribs on concave side of shaft, shaft tapering to narrow rounded apex (Fig. 20 E–G); some uncini lacking ribs (Fig. 20F); uncini not observed on last 2–3 thoracic setigers. Abdominal neurosetae with 2–3 capillaries, these smooth, barbs not observed; a short thin sharply pointed acicula present.

Pygidium with two anal cirri.

Variability. Larger specimens typically have 16–17 thoracic setigers and branchiae from setigers 13 or 14. However, smaller specimens such as a complete paratype (USNM 1621037) have 56 setigers, is 7.0 mm long with 11 thoracic setigers and branchiae from setiger 10. The juvenile reported above measures 5.5 mm long with 9 thoracic setigers and branchiae from setiger 10.

All specimens, juvenile or adult, have an unusually long, narrow, pointed prostomium; distinct glandular bands across the dorsum; short, glandular subpodial flanges; and at least some evidence of interramal processes in abdominal setigers. Ventral bands of glands are prominent in adults but are not well developed in juveniles. The juvenile has two peristomial rings that are merged in the adults. This same pattern where the two peristomial rings of postlarvae and juveniles merge and produce a single peristomial ring in adults has been reported for species of Naineris (Okuda 1946; Blake 1980, 2000; Giangrande & Petraroli 1991). This is the first report of such a peristomial change in a species of Scoloplos.

Remarks. Scoloplos pettiboneae n. sp. is a distinctive species along the U.S. Atlantic coast in having an unusually long, narrowly pointed prostomium and the absence of any extra subpodial lobes or papillae associated with the posterior thoracic or abdominal setigers. The species has a short interramal dorsal process or protuberance, but no cirrus, between the noto- and neuropodia of abdominal segments and has prominent dorsal and ventral glandular bands on the middle and posterior thoracic setigers and dorsal patches that continue on to a few anterior abdominal segments; these glands and associated bands stain with Rose Bengal and Shirlastain A. Scoloplos pettiboneae n. sp., like many other orbiniids, has prominent subpodial flanges, but in this species the flanges are thin and short, with numerous glands that stain with Rose Bengal and Shirlastain A and that appear as flaps along anterior and posterior abdominal segments.

Scoloplos pettiboneae n. sp. is most similar to S. acmeceps Chamberlin, 1919a from the U.S. Pacific coast. Several specimens of S. acmeceps from low intertidal sediment in Tomales Bay, California, were examined and compared with S. pettiboneae n. sp. Scoloplos acmeceps is a larger species with up to 200 segments and 150 mm long according to Hartman (1957). The Tomales Bay specimens are shorter, with about 180 segments and 50 mm long. They exhibit thin glandular bands dorsally and ventrally across the thorax as in Scoloplos pettiboneae n. sp., but the bands are not as prominent and do not retain stain. In addition, the subpodial flanges of S. acmeceps, while thin, are not glandular and do not retain stain. The short interramal process observed in S. pettiboneae n. sp. is not present on the Tomales Bay specimens of S. acmeceps and is not reported or illustrated by Hartman (1957). Interestingly, the last thoracic segment (19) of the Tomales Bay specimens is transitional in having a semicircular subpodial flange that continues as the more elongate flanges of the abdominal segments. This is the same pattern described here for S. pettiboneae n. sp. and has not been previously reported for S. acmeceps and further supports the similarity between the two species.

Etymology. This species is named for the late Dr. Marian H. Pettibone, in recognition of her studies of the polychaete fauna of New England and revisionary work on the Orbiniidae.

Distribution. Off New England, Massachusetts Bay 29–45 m; Georges Bank, 62– 150 m.