Scoloplos pseudoarmiger, Blake, 2021

Blake, James A., 2021, New species and records of Orbiniidae (Annelida, Polychaeta) from continental shelf and slope depths of the Western North Atlantic Ocean, Zootaxa 4930 (1), pp. 1-123 : 47-54

Scoloplos pseudoarmiger new species

Figures 21–24

urn:lsid:zoobank.org:act:F61D4F4C-B4C4-486F-8234-64EF1EE566C8

Scoloplos armiger: Maciolek-Blake et al. 1985 : B-5; Blake et al. 1998: C-1, C-2 (in part). Not Müller 1776.

Material examined. (21 specimens) Northeastern USA, Georges Bank, Benthic Infauna Monitoring Program (1981–1984), coll. G.W. Hampson, Chief Scientist. Sta. 10: Cruise M 12, R/ V Gyre, Rep. 6, 03 Jun 1984, 40°42.0′N, 68°35.3′W, 66 m, holotype ( USNM 1620928 ). Sta. 1: Cruise M 4, R/ V Cape Henlopen, Rep. 1, 12

May 1982, 41°13.0′N, 67°15.3′W, 58 m, 1 paratype ( USNM 1620929 ) . Cruise M5, R/V Oceanus, Rep. 6, 22 Jul 1982, 41°13.0′N, 67°15.3′W, 53 m (1, USNM 1620930 ) ; Cruise M 8, R/ V Gyre, Rep. 3, 15 May 1983, 41°13.0′N, 67°15.3′W, 57 m, 1 paratype ( USNM 1620931 ) ; Cruise M10, R/V Oceanus, Rep. 3, 15 Nov. 1983, 41°13.0′N, 67°15.3′W, 55 m (1, USNM 1620932 ) . Sta. 4: Cruise M 6, Rep. 6, 22 Nov 1982, 40°50.7′N, 68°00.2′W, 65 m (1, USNM 162939 ) ; Cruise M 8, R/ V Gyre, Rep. 3, 19 May 1983, 40°50.7′N, 68°00.2′W, 66 m, 1 paratype ( USNM 1620933 ) ; Cruise M11, R/V Oceanus, Rep. 1, 02 Feb 1984, 40°50.7′N, 68°00.2′W, 67 m (1, USNM 1620934 ) ; Cruise M 12, R/ V Gyre, Rep. 4, 04 Jun 1984, 41°13.0′N, 67°15.3′W, 55 m, 1 paratype ( USNM 1620935 ) . Sta. 10: Cruise M 2, R/V Oceanus, Rep. 5., 12 Nov. 1981, 40°42.0′N, 68°35.3′W, 60 m, 1 paratype ( USNM 1620936 ) ; Cruise M 12, R/ V Gyre, Rep. 4, 03 Jun 1984, 40°42.0′N, 68°35.3′W, 66 m, 1 paratype ( USNM 1620937 ) . Sta. 5-29: Cruise M 6, R/V Oceanus, Rep. 2, 24 Nov 1982, 40°39.5′N, 67°50.4′W, 81 m, 1 paratype ( USNM 1620938 ) .— Massachusetts Bay , MWRA Harbor & Outfall Monitoring Program. 1996 August Survey: Sta. NF 13, Rep. 1, 42°23.40′N, 70°49.35′W, 33 m (1, MCZ 161613 ) .

Description. A moderate to large, elongate species; thoracic segments dorsoventrally flattened, abdominal segments ventrally rounded, dorsally flattened, with elevated parapodia; abdominal segments flattened dorsally, rounded ventrally. Shallow mid-dorsal groove present in thoracic segments; narrow mid-ventral groove present along most of body. Holotype complete, with 172 setigers, 31.3 mm long and about 0.8 mm wide across dorsum of thorax; thorax with 20 setigers and branchiae from setiger 16 ( Fig. 23B ). Other specimens with 16–20 thoracic segments and branchiae from setigers 13–16 ( Fig. 21A ). Smaller specimens (<25 mm long) with fewer thoracic setigers and earlier start of branchiae. Transition from thorax to abdomen gradual, with last defined thoracic setiger lacking uncini; subsequent setigers transitioning with neuropodium becoming enlarged and reduced number of capillaries. Body segments uniannulate in thoracic region, becoming biannulate in abdominal segments, with each parapodium separated from following one by a wide intersegmental band ( Fig. 23F ). Color in alcohol light tan; subpodial flanges of most abdominal neuropodia glandular, darkly pigmented ( Figs. 22 C–D, 23F).

Pre-setiger region narrow, triangular, as long as first three setigers ( Figs. 21 A–C, 23A–B, D). Prostomium long, divided into anterior and posterior sections ( Fig. 21 A–C), with narrow anterior section tapering to pointed tip, separated laterally and ventrally from larger posterior section bearing nuchal organs as semi-circular slits on posterior lateral margin and anterior to mouth ventrally ( Fig. 21 B–C); eyespots absent. Peristomium a single ring, with lateral groove ( Fig. 21B ), about as long as first setiger; smooth dorsally, surrounding mouth ventrally, forming upper and lower lips ( Fig. 21C ); upper lip of mouth with two thickened transverse lobes; lower lip with about seven narrow elongate lobes. Holotype with proboscis everted, consisting of two rounded lobes ( Fig. 23B, D ). Lower lip of mouth extending mid-ventrally onto setiger 1 ( Fig. 21C ).

Anteriormost 3–4 thoracic notopodia with no apparent postsetal lobe; from about setiger 5–6 a short, broadly triangular but low postsetal lobe appears ( Fig. 22A ), continuing to about setiger 13–14, thereafter lobe lengthening, becoming digitiform, arising from narrow base ( Fig. 22B ), continuing onto abdominal setigers. Thoracic neuropodia with low, broadly rounded base; first 3–4 thoracic neuropodia with no apparent postsetal lobe; from about setiger 5, a short semi-circular papillate lobe appears ( Fig. 22A ) that begins lengthening and transitioning to a short digitiform lobe over subsequent segments; posterior thoracic setigers with a narrow digitiform postsetal lobe arising from a broad, rounded base. Last 1–3 thoracic neuropodia developing 1–3 extra subpodial lobes or papillae ( Figs. 22B , 23E arrows); thoracic neuropodial postsetal lobe thickening and elongating in anterior neuropodia becoming incorporated into abdominal neuropodium; second thoracic postsetal lobe retained ventral to abdominal neuropodium, transforming into subpodial flange over subsequent segments ( Fig. 22C ); 1–2 additional ventral-most postsetal lobes or papillae retained as subpodial papillae over a few anterior abdominal neuropodia ( Fig. 22C ). Abdominal neuropodia becoming thicker, apically divided into two parts separated by notch from which setae emerge ( Fig. 22 C–D); medial lobe longer, pointed; lateral lobe shorter, rounded apically. Each abdominal neuropodium with short, rounded subpodial flange; one subpodial papilla ventral to flange on 5–10 anterior abdominal segments ( Fig. 22C ). Subpodial flanges of most abdominal setigers relatively short, thickened, with numerous internal glands; these glands darkly pigmented on most specimens ( Figs. 22D , 23F , 24D ). Interramal cirrus absent, but patch of sensory cilia present between noto- and neuropodia along most of abdomen ( Figs. 22 C–D, 24D arrows).

Branchiae first present from posterior thoracic setigers 13–16; branchiae short at first, triangular, becoming longer and full size by first abdominal segment ( Fig. 21A ); each anterior branchia broad, tapering to narrow rounded tip ( Fig. 22 B–C); subsequent branchiae longer, triangular, asymmetrical ( Figs. 22D , 24D ). Each branchia thickly ciliated along lateral and medial margins ( Figs. 22 B–D, 24D arrows).

Thoracic notosetae long camerated capillaries arranged in 2–3 rows. Thoracic neurosetae arranged in four rows of numerous uncini and a fifth row of camerated capillaries; about 10 or more uncini in each row ( Figs. 21B , 22A , 23C ); uncini occurring on all thoracic setigers except last, being transitional to abdominal setigers. Individual uncini with shafts smooth on concave side, tapering to narrow, rounded tip; some uncini with distinct hood behind smooth tip; convex side of shaft flattened, bearing rows of transverse ribs ( Figs. 21D , 24 A–C). Abdominal notosetae thin capillaries and 1–2 furcate setae; capillaries with camerated shafts; furcate setae with unequal tynes, each tyne with blunted tip and apical notch; tynes each with row of thin needles extending medially ( Fig. 21E ). Abdominal neurosetae with up to 5–6 thin capillaries, each mostly smooth but some with short barbs along one edge, and 1–2 curved aciculae, sometimes protruding, with rounded tip. Flail setae not observed.

Pygidium short, with two short dorsal lobes, two large lateral lobes, and one short, rounded ventral lobe ( Fig. 21 F–G); all lobes surrounding anal opening; two long, narrow anal cirri arising dorsally ( Figs. 21F , 24E ).

Remarks. Scoloplos pseudoarmiger n. sp. belongs to a group of Scoloplos species with numerous rows of uncini in the thoracic neuropodia and extra subpodial lobes or papillae in posterior thoracic and anterior abdominal neuropodia. In this respect, S. pseudoarmiger n. sp. is the only species of the genus to have this combination of characters along the U.S. Atlantic coast. According to Hartmann-Schr̂der (1971, 1996) and Zhadan (1998) northern European specimens of S. armiger belong in this category. However, McIntosh (1910) describes S. armiger specimens from Britain as having few thoracic neuropodial uncini. As noted earlier, recent field investigations have demonstrated that at least two species of Scoloplos that are ecologically and reproductively isolated from one another occur in the North Sea (Kruse & Reise 2003; Kruse et al. 2003, 2004). These results from the North Sea were supported by Bleidorn et al. (2006) using molecular data that also identified a third species from Norway near the type-locality of S. armiger . To date, however, none of these three potential European species have been redescribed and separated from one another with morphological data. In the present study, S. pettiboneae n. sp., S. pseudoarmiger n. sp., and S. verrilli n. sp. represent a similar group of three closely related nearshore and shelf species that are easily separated from one another by distributional patterns and different morphologies.

Scoloplos pseudoarmiger n. sp., in having multiple rows of uncini in thoracic neuropodia, is most similar morphologically to northern European specimens of S. armiger sensu Hartmann-Schr ̂der (1996) and Zhadan (1998). At this time, however, there is insufficient information to know if the two European reports represent the same species. However, the majority of specimens reported by Zhadan (1998) were from Arctic and sub-Arctic habitats whereas Hartmann-Schr̂der (1996) reported specimens from north of Germany and the North Sea. The present records of S. pseudoarmiger n. sp. are from shelf depths in temperate latitudes. Important characters from these reports of S. armiger are compared with S. pseudoarmiger n. sp. in Table 1 .

(1998) with Scoloplos pseudoarmiger n. sp.

Based on the information presented in Table 1 , Scoloplos armiger and S. pseudoarmiger n. sp. have similar numbers of setigerous segments, numbers of thoracic setigers, and first branchiae from posterior thoracic setigers. Scoloplos pseudoarmiger n. sp. differs from the two European reports of S. armiger in details of the prostomium, peristomium, distribution of the subpodial lobes and papillae over thoracic and abdominal setigers, and morphology of the abdominal subpodial flanges. While details of the upper and lower lips of the mouth and segmental annulation patterns along the body may be important, they were not reported for the European species.

The first extra subpodial lobe that occurs in posterior thoracic setigers of S. pseudoarmiger n. sp. is shown in the present study to represent a transitional phase in the development of the subpodial flange ventral to the abdominal neuropodia. The resulting flanges are short and oval in shape and have numerous pigmented internal glands. The subpodial flange of the European reports of S. armiger is more elongate and lacks internal glands.

Etymology. The epithet is from pseudo, Greek for false combined with armiger , the most common species name in the genus Scoloplos . According to Wikipedia, “an armiger in heraldry is a person entitled to use a heraldic achievement (e.g., bear arms, an ‘armour-bearer’) either by hereditary right, grant, matriculation, or assumption of arms.” According to Webster, armiger means (1) squire, (2) one entitled to bear heraldic arms. The term is from Medieval Latin.

Distribution. Massachusetts Bay, 33 m; Georges Bank, 53– 93 m.

Figures

FIGURE 21. Scoloplos pseudoarmiger n. sp. A, anterior end, dorsal view; B, anterior left lateral view; C, anterior end, ventral view; D, thoracic neuropodial uncini; E, furcate seta; F, pygidium, dorsal view; G, pygidium, ventral view. A–D (USNM 1620929); E–G (USNM 1620935).

FIGURE 22. Scoloplos pseudoarmiger n. sp. Paratype (USNM 1620929): A, thoracic setiger 7, anterior view; B, thoracic setiger 14, anterior view; C, anterior abdominal setiger 25; D, middle abdominal setiger, ca. setiger 40.

FIGURE 23. Scoloplos pseudoarmiger n. sp. A, anterior end, paratype, left lateral view; B, anterior end, holotype, right lateral view; C, middle thoracic setigers, paratype; D, pre-setiger region, and setigers 1–2 of holotype, right lateral view; E, transitional area between thorax and abdomen, right lateral view (arrows denote subpodial lobe); F, abdominal parapodia, right lateral view with subpodial flanges noted. A, C, F, paratype (USNM 1620929); B, D, holotype (USNM 1620928); E, (USNM 1620938). All stained with Shirlastain A.

FIGURE 24. Scoloplos pseudoarmiger n. sp. A, rows of thoracic neuropodial uncini, setiger 6; B, close up of same; C, three uncini showing transverse ribs across shaft; D, abdominal setiger, posterior view (arrows denote cilia); E, pygidium.A–D, paratypes (USNM 1620929); E, holotype (USNM 1620928). D–F stained with Shirlastain A.