Scoloplos intermedius ( Hartman, 1965 )

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 : 31-37

Scoloplos intermedius ( Hartman, 1965)

Figures 12–14

Haploscoloplos fragilis intermedius Hartman, 1965: 128 , pl. 28, fig. a; Hartman & Fauchald 1971: 91 (in Part). Fide Mackie 1987.

Scoloplos intermedius: Mackie 1987: 23–24 , fig. 23.

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

Scoloplos sp. 2: Blake et al. 1987: C-4; Hilbig 1994: 942.

Material examined. (119 specimens) Northeastern USA, off New England, Gay-Head Bermuda Transect, R/V Atlantis, Sta. F-1, 24 May 1961, 39°47′N, 70°45′W, 1500 m, holotype ( LACM-AHF Poly 0686).— US North Atlantic ACSAR program, off New England, coll. G.W Hampson, Chief Scientist. Sta. 3: Cruise NA-2, Rep. 1, 26 Apr 1985, 41°01.34′N, 66°20.21′W, 1340 m (1, USNM 1620941 ); Cruise NA-3, Rep. 2, 03 Jul 1985, 41°01.38′N, 66°20.22′W, 1330 m (3, USNM 1620942 ). Sta. 9: Cruise NA-2, Rep. 1, 03 May 1985, 39°50.43′N, 70°01.58′W, 1235 (1, USNM 1620943 ). Cruise NA-4, Rep. 1, 27 Nov 1985, 39°50.42′N, 70°01.65′W, 1224 m (1, USNM 1620944 ); Rep. 3, 27 Nov 1985, 39°50.39′N, 70°01.65′W, 1239 m (1, USNM 1620945 ); Cruise NA-5, Rep. 3, 03 May 1986, 39°50.39′N, 70°01.62′W, 1238 m (1, USNM 1620946 ); Cruise NA-6, Rep. 2, 28 Jul 1986, 39°50.41′N, 70°01.62′W, 1230 m (2, USNM 1620947 ). Sta. 10: Cruise NA-2, Rep. 1, 03 May 1985, 39°48.11′N, 70°05.26′W, 1210 m (2, USNM 1620948 ); Rep. 3, 03 May 1985, 39°48.12′N, 70°05.24′W, 1210 m (1, USNM 1620949 ); Cruise NA-4, Rep. 1, 27 Nov 1985, 39°48.09′N, 70°05.29′W, 1222 m (1, USNM 1620950 ); Rep. 3, 30 Nov 1985, 39°48.38′N, 70°54.96′W, 1244 m (1, USNM 1620951 ). Sta. 13: Cruise NA-4, Rep. 1, 29 Nov 1985, 39°48.37′N, 70°55.12′W, 1244 m (1, USNM 1620952 ); Cruise NA-6, Rep. 2, 30 Jul 1986, 39°48.25′N, 70°54.95′W, 1273 m (1, USNM 1620953 ). Sta. 15: Cruise NA-2, Rep.1, 05 May 1985, 39°40.08′N, 70°54.26′W, 2150 m (1, USNM 1620954 ).— Off New Jersey and Delaware, U.S. Mid-Atlantic ACSAR program, coll. R.M. Petrecca, Chief Scientist. Sta.

2: Cruise Mid-1, Rep. 1, 01 Apr 1984, 38°35.78′N, 72°53.65′W, 2013 m (1, USNM 1620955 ) ; Cruise Mid-2, Rep. 2, 03 Aug 1984, 38°35.74′N, 72°53.68′W, 2014 m (1, USNM 1620956 ) ; Rep. 3, 03 Aug 1984, 38°35.76′N, 72°53.81′W, 2004 m (1, USNM 1620957 ) ; Cruise Mid-3, Rep. 1, 02 Dec 1984, 38°35.75′N, 72°53.67′W, 2010 m (1, USNM 1620958 ) ; Cruise Mid-5, Rep. 1, 05 Aug 1985, 38°35.68′N, 72°53.79′W, 2010 m (1, USNM 1620959 ) ; Cruise Mid-6, Rep. 2, 13 Nov 1985, 38°35.65′N, 72°53.70′W, 2024 m (1, USNM 1620960 ) . Sta. 3: Cruise Mid-1, Rep. 1, 05 May 1984, 38°36.88′N, 72°51.41′W, 2055 m (1, USNM 1620961 ) ; Rep. 2, 05 May 1984, 38°36.88′N, 72°51.34′W, 2055 m (1, USNM 1620962 ) ; Cruise Mid-2, Rep. 3, 03 Aug 1984, 38°36.84′N, 72°51.46′W, 2056 m (2, USNM 1620963 ) ; Cruise Mid-5, Rep. 1, 05 Aug 1985, 38°36.79′N, 72°51.54′W, 2050 m (1, USNM 1620964 ) . Sta. 5: Cruise Mid-1, Rep. 2, 04 May 1984, 38°50.53′N, 72°33.10′W, 2065 m (2, USNM 1620965 ) ; Cruise Mid-3, Rep. 3, 05 Dec 1985, 38°50.47′N, 72°33.07′W, 2070 m (1, USNM 1620966 ) ; Cruise Mid-5, Rep. 1, 03 Aug 1985, 38°50.44′N, 72°33.18′W, 2077 m (1, USNM 1620967 ) ; Rep. 3, 03 Aug 1985, 38°50.42′N, 72°33.24′W, 2080 m (2, USNM 1620968 ) ; Cruise Mid-6, Rep. 1, 11 Nov 1985, 38°50.49′N, 72°33.17′W, 2084 m (1, USNM 1620969 ) . Sta. 6: Cruise Mid-2, Rep. 1, 01 Aug 1984, 39°05.65′N, 72°02.97′W, 2084 m (1, USNM 1620970 ) . Sta. 9: Cruise Mid-2, Rep. 1, 06 Aug 1984, 38°17.24′N, 73°14.51′W, 2109 m (1, USNM 1620971 ) . Sta. 10: Cruise Mid-1, Rep. 2, 07 May 1984, 38°51.80′N, 73°19.96′W, 2095 m (1, USNM 1620972 ) . Sta. 11: Cruise Mid-1, Rep. 1, 07 May 1984, 38°40.16′N, 72°56.82′W, 1515 m (1, USNM 1620973 ) ; Rep. 3, 07 May 1984, 38°40.22′N, 72°56.27′W, 1520 m (1, USNM 1620974 ) ; Cruise Mid-2, Rep. 3, 05 Aug 1984, 38°40.25′N, 72°56.24′W, 1504 m (2, USNM 1620975 ) ; Cruise Mid-3, Rep. 1, 04 Dec 1984, 38°40.13′N, 72°56.27′W, 1540 m (1, USNM 1620976 ) ; Rep. 3, 04 Dec 1984, 38°40.14′N, 72°56.35′W, 1520 m (2, USNM 1620977 ) ; Cruise Mid-4, Rep. 1, 17 May 1985, 38°40.10′N, 72°56.43′W, 1510 m (3, USNM 1620978 ) ; Rep. 3, 17 May 1985, 38°40.11′N, 72°56.44′W, 1510 m (3, USNM 1620979 ) ; Cruise Mid-5, Rep. 1, 06 Aug 1985, 38°40.12′N, 72°56.45′W, 1505 m (2, USNM 1620980 ) ; Rep. 2, 06 Aug 1985, 38°40.12′N, 72°56.47′W, 1502 m (2, USNM 1620981 ) ; Rep. 3, 06 Aug 1985, 38°40.14′N, 72°56.46′W, 1502 m (3, USNM 1620982 ) . Cruise Mid-6, Rep. 1, 38°40.13′N, 72°56.48′W, 1504 m (1, USNM 1620983 ) . Sta. 13: Cruise Mid-1, Rep. 1, 02 Apr 1984, 37°53.33′N, 73°45.09′W, 1613 m (3, USNM 1620984 ) ; Rep. 2, 02 Apr 1984, 37°53.38′N, 73°45.10′W, 1613 m (1, USNM 1620985 ) ; Rep. 3, 02 Apr 1984, 37°53.36′N, 73°45.10′W, 1613 m (1, USNM 1620986 ) ; Cruise Mid-2, Rep. 1, 07 Aug 1984, 37°53.35′N, 73°45.01′W, 1614 m (2, USNM 1620987 ) ; Cruise Mid-3, Rep. 1, 30 Nov 1984, 37°53.32′N, 73°45.10′W, 1615 m (2, USNM 1620988 ) ; Rep. 2, 30 Nov 1984, 37°53.35′N, 73°45.00′W, 1615 m (4, USNM 1620989 ) ; Rep. 3, 30 Nov 1984, 37°53.29′N, 73°45.11′W, 1612 m (1, USNM 1620990 ) ; Cruise Mid-4, Rep. 1, 19 May 1985, 37°53.26′N, 73°45.25′W, 1615 m (3, USNM 1620991 ) ; Rep. 2, 19 May 1985, 37°53.29′N, 73°45.30′W, 1607 m (2, USNM 1620992 ) ; Cruise Mid-5, Rep. 1, 09 Aug 1985, 37°53.26′N, 73°45.21′W, 1607 m (3, USNM 1620993 ) ; Rep. 2, 09 Aug 1985, 37°53.27′N, 73°45.28′W, 1605 m (3, USNM 1620994 ) ; Cruise Mid-6, Rep. 1, 16 Nov 1985, 37°53.31′N, 73°45.30′W, 1609 m (3, USNM 1620995 ) ; Rep. 3, 16 Nov. 1985, 37°53.23′N, 73°45.27′W, 1607 m (1, USNM 1620996 ) . Sta. 14: Cruise Mid-1, Rep. 3, 02 Apr 1984, 37°53.79′N, 73°44.78′W, 1503 m (6, USNM 1620997 ) ; Cruise Mid-4, Rep. 3, 19 May 1985, 37°53.82′N, 73°44.76′W, 1490 m (3, USNM 1620998 ) ; Cruise Mid-5, Rep. 1, 10 Aug 1985, 37°53.79′N, 73°44.78′W, 1490 m (3, USNM 1620999 ) ; Rep. 2, 10 Aug 1985, 37°53.79′N, 73°44.79′W, 1490 m (2, USNM 1621000 ) ; Rep. 3, 10 Aug 1985, 37°53.80′N, 73°44.74′W, 1490 m (2, USNM 1621001 ) ; Cruise Mid-6, Rep. 1, 15 Nov. 1985, 37°53.69′N, 73°44.69′W, 1515 m (2, USNM 1621002 ) ; Rep. 2, 15 Nov. 1985, 37°53.80′N, 73°44.74′W, 1494 m (1, USNM 1621003 ) .— Southeastern USA, US South Atlantic ACSAR program, coll. J.A. Blake, Chief Scientist. off Cape Lookout, North Carolina, Sta. 2: Cruise SA-3, Rep. 1, 15 Jul 1984, 34°15.00′N, 75°43.70′W, 1002 m (2, USNM 1621004 ) . Sta. 3: Cruise SA-3, Rep. 3, 14 Jul 1984, 34°15.10′N, 75°40.30′W, 1189 m (2, USNM 1621005 ) . Sta. 4: Cruise SA-2, Rep. 1, 20 May 1984, 34°11.70′N, 75°38.60′W, 2064 m (1, USNM 1621006 ) ; Rep. 2, 20 May 1984, 34°11.90′N, 75°38.70′W, 2029 m (1, USNM 1621007 ) ; Rep. 3, 20 May 1984, 34°11.50′N, 75°39.00′W, 1969 m (3, USNM 1621008 ) ; Cruise SA-3, Rep. 1, 13 Jul 1984, 34°12.10′N, 75°38.60′W, 2066 m (3, USNM 1621009 ) ; Rep. 2, 14 Jul 1984, 34°10.41′N, 75°39.10′W, 2005 m (2, USNM 1621010 ) ; Rep. 3, 14 Jul 1984, 34°11.17′N, 75°38.98′W, 2006 m (1, USNM 1621011 ) ; Cruise SA-4, Rep. 1, 23 May 1985, 34°11.29′N, 75°38.67′W, 2015 m (1, USNM 1621002 ) ; Rep. 2, 23 May 1985, 34°11.22′N, 75°38.44′W, 2015 m (1, USNM 1621013 ) ; Rep. 3, 23 May 1985, 34°11.29′N, 75°38.67′W, 2015 m (3, USNM 1621014 ) . Cruise SA-5, Rep. 1, 24 Sep 1985, 34°11.27′N, 75°38.63′W, 2032 m (1, USNM 1621015 ) . Off Charleston, South Carolina, Sta. 14: Cruise SA-4, Rep. 1, 20 May 1985, 32°23.64′N, 77°01.13′W, 805 m (1, USNM 1621016 ) .

Description. A small to moderately sized species, all specimens except juveniles incomplete. Holotype 11 mm long, 0.80 mm wide across thorax with 37 setigers (Mackie 1987); new collections with four specimens having 50 or more setigers, 12–15 mm long, and 1–1.2 mm wide across thorax: USNM 1620962: 14 mm long, 1.2 mm wide, 50 setigers, 12 thoracic setigers, and branchiae from setiger 11; USNM 1620942: 13 mm long, 1.1 mm wide, 52 setigers, 13 thoracic setigers, and branchiae from setiger 12; USNM 1620995: 15 mm long, 1.2 mm wide, 54 setigers, 13 thoracic setigers, and branchiae from setiger 10; USNM 1620960: 12 mm long, 1.0 mm wide, 55 setigers, 13 thoracic setigers and, branchiae from setiger 10.

Thoracic setigers numbering 11–13 in larger specimens; 6–10 in juveniles. Thoracic segments short, dorsoventrally flattened, 5–6 times wider than long ( Fig. 12A ) with middle thoracic segments often with weak mid-dorsal groove. Abdominal segments ventrally rounded, dorsally flattened with elevated parapodia; anterior and middle abdominal setigers with intersegmental grooves of venter narrow, bordered with flattened bands on anterior and posterior sides; parapodia located between bands of two segments producing a triannulate appearance; posterior parapodia more crowded, with intersegmental bands not apparent. Shallow ventral groove present along entire body on most specimens; dorsal grooves and ridges absent. Transition from thorax to abdomen denoted by elongation of neuropodium, with split apex developing over 1–2 successive segments ( Fig. 12A, C ). Color in alcohol light tan. Subpodial flanges of middle and posterior abdominal neuropodia often with internal glands but these not pigmented as in other species.

Pre-setiger region triangular in shape, as long as first 2–3 setigers ( Fig. 12 A–C). Prostomium conical, tapering to pointed tip; nuchal organs vertical curved slits on posterior lateral margin; eyespots absent. Peristomium longer than first setiger, with a single smooth annular ring dorsally ( Fig. 12A ), surrounding mouth on ventral side, forming upper and lower lips ( Fig. 12B ); upper lip of mouth with two large protruding lobes anterior to several small rounded lobes; lower lip of mouth with six large, elongate lobes ( Fig. 12B ).

Thoracic notopodia triangular, tapering to narrow digitiform postsetal lobe, short at first, then becoming longer, narrow in middle and posterior thoracic segments ( Fig. 13A ). Thoracic neuropodia with digitiform postsetal lobe arising from a broadly rounded base, lobes short at first, becoming long and fingerlike ( Fig. 13 A–C). Transition to abdominal segments abrupt, with neuropodium becoming larger, elongate, and apically divided into two lobes separated by a notch from which setae arise ( Fig. 13 B–C); medial lobe thick, rounded; ventral lobe narrower, shorter, rounded apically. Interramal cirrus present in anterior abdominal setigers as short conical lobe ( Fig. 13B ), reduced to thick variously developed process in posterior setigers ( Fig. 13C ). Each abdominal neuropodium with narrow subpodial flange; with 1–2, rarely 3, subpodial papillae on anterior abdominal segments with one papilla usually arising from basal margin of subpodial flange ( Fig. 13B ); single papilla continuing through middle abdominal setigers ( Fig. 13C ), absent in posterior setigers. Subpodial flanges of middle and posterior abdominal setigers with numerous internal glands ( Fig. 13C ), but these not darkly pigmented as on related species.

Branchiae from posterior thoracic setiger 10–12 ( Fig. 12A, C ); branchiae elongate, generally triangular in shape, tapering to narrow papillate tip ( Fig. 13B ); branchiae of middle and posterior setigers becoming broader, and irregular in shape ( Fig. 13C ), rarely asymmetrical. Each branchia ciliated along lateral and medial margins.

Thoracic notosetae numerous, thick, long, camerated capillaries arranged in 4–5 rows. Thoracic neurosetae arranged in about five rows with similar appearing camerated capillaries and 3–6 uncini concentrated in lower part of setal fascicle; uncini observed on all thoracic setigers of larger specimens; juveniles with irregular number of uncini not observed on all thoracic setigers. Individual uncini with shafts smooth on convex side tapering to narrow, rounded tip; concave side of shaft flattened, bearing low transverse ribs along most of shaft ( Fig. 13 D–E); tip of shaft sometimes with hood formed of emergent fibrils ( Fig. 13D ). Abdominal notosetae thin, camerated capillaries and 1–2 furcate setae. Furcate setae with unequal tynes ( Fig. 13F ), long tyne with blunted tip and an apical notch; shorter tyne with rounded tip; each tyne with a row of thin needles extending into center toward other tyne. Abdominal neurosetae with up to 4–5 thin smooth capillaries, barbs not observed in light microscope, and 1–2 curved aciculae, sometimes protruding, with rounded tip. Flail setae not observed.

Pygidium observed only on a few juveniles as a pair of rounded lobes surrounding anal opening and with two thin anal cirri arising dorsally ( Fig. 12D , 14E ).

Juvenile morphology. Although none of the samples contained large numbers of specimens, sufficient numbers of juveniles were present to document some aspects of their morphology and the stage in development when certain key characters of adults become present. Specimens from NA-6, Sta. 9 (USNM 1620947) and Mid-4, Sta. 11 (USNM 1620978) were studied in some detail.

A 15-setiger juvenile from NA-6, Sta. 9 (USNM 1620947) is 1.3 mm long and 150 µm wide across thoracic setigers ( Fig. 14A ). The body is relatively thick throughout with six distinctive thoracic setigers and nine crowded abdominal setigers. Branchiae are present on setigers 14 and 15 ( Fig. 14A ). The pre-setiger region appears to be fully developed. The prostomium is adult-like in being triangular and tapering to a narrow, rounded apex ( Fig. 14 A–B); nuchal organs were not observed. The peristomium consists of a single ring that is relatively smooth dorsally and surrounds the mouth ventrally. At this stage the upper lip of the mouth has only two weakly developed lobes and the ventral lip is a single ridge lacking lobes. The specimen had been feeding however, as silt particles were pres- ent in the gut. Parapodia are generally well developed; thoracic postsetal lobes are only short papillae; abdominal notopodia are short thick lobes; abdominal neuropodia are short and thick, with no evidence of the bilobed nature of adults. An interramal cirrus is present on the last setiger. All notosetae are camerated capillaries, furcate setae were not observed; thoracic neurosetae include camerated capillaries and 2–4 hooks or uncini bearing a row of transverse barbs or ridges along the shaft; abdominal neurosetae include 2–3 long capillaries. The pygidium is a rounded lobe with two short papillae that are anlage of anal cirri ( Fig. 14A ).

A 31-setiger pre-adult from Sta. Mid-4, Sta. 11 (USNM 1620978) is 3.2 mm long and about 150 µm wide anteriorly and 120 µm wide in middle segments ( Fig. 14E ). The body is long and thin, with middle segments that are up to twice as long as wide and appear weakly moniliform and distended guts due to ingested sediments. There are six thoracic setigers and branchiae are present from setiger 15. The first interramal cirri were observed on setiger 8 as short triangular lobes. The pre-setiger region is about the same as with the smaller specimen from NA-6. Thoracic notosetae include about 15 camerated capillaries; abdominal notosetae include 5–10 camerated capillaries and a single furcate seta was observed. Thoracic neurosetae include about 25 capillaries and 2–4 hooks or uncini with transverse barbs across the shafts ( Fig. 14D ); abdominal neurosetae include a few long capillaries and 1–2 short, pointed aciculae. The pygidium bears two long anal cirri ( Fig. 14E ).

Variability. In adults, the shape of the interramal cirrus varies from a short, rounded or triangular-shaped lobe to an elongate cirrus. Except for always being shorter than either the noto- or neuropodium, there is no consistency in this character even within specimens from the same sample. The thoracic neuropodial uncini are generally consistent in morphology among specimens except for the apical hood which can be either absent or worn.

Remarks. This species was originally described as Haploscoloplos fragilis intermedius by Hartman (1965) from deep-water collections off New England collected by the late Dr. Howard Sanders. Additional materials were reported by Hartman & Fauchald (1971) from the same general area. Mackie (1987), as part of a revision of the genus Leitoscoloplos , determined that upper slope (ca. 300 m) and lower slope (ca. 1500 m) specimens reported by Hartman (1965) as H. fragilis intermedius represented two different species. Mackie (1987) described the upper slope specimens as a new species, L. obovatus (see above). He also determined that the specimens reported by Hartman from the deeper slope locations represented a species of Scoloplos and raised the subspecies to full species status, S. intermedius .

The new collections of S. intermedius reported here are from middle and lower continental slope depths from along the entire U.S. Atlantic continental margin from near the Canadian boundary to the Carolinas. Scoloplos intermedius is the only North Atlantic species of the genus known to have an interramal cirrus and the only species from the Western North Atlantic to occur in deep water (1200–2100 m). Scoloplos papillatus n. sp. (see below) from off Cape Hatteras, North Carolina is an upper slope depths (600–800 m) species that lacks interramal cirri.

Scoloplos intermedius is most similar to S. similis Mackie, 1987 from off South Africa in shelf depths (124 m) by having an interramal cirrus between the noto- and neuropodia of the last thoracic and anterior abdominal setigers and subpodial papillae that continue along most of the abdominal segments. The two species differ in that S. intermedius has 11–13 thoracic setigers and branchiae from setigers 10–12, whereas S. similis has 15 thoracic setigers and branchiae from setiger 12. Both species have subpodial papillae and subpodial flanges; however, the subpodial flanges of S. intermedius are thick and glandular in abdominal setigers and with a subpodial papilla. In contrast the subpodial flanges of S. similis are short and separated from the neuropodium by a distinct notch; internal glands in the subpodial flanges were not reported by Mackie (1987). Furcate notosetae are present in abdominal segments of S. intermedius but were not present in the three specimens of S. similis examined by Mackie (1987).

Juveniles described here indicate that the interramal cirrus and thoracic neuropodial uncini develop early, while the final number of thoracic setigers and position of the branchiae develop later. Interestingly, the nature of the presetiger region of the smallest juveniles closely resembles that of adults.

Distribution. Continental slope off the U.S. Atlantic coast, New England to North Carolina, 1210–2109 m.

Figures

FIGURE 12. Scoloplos intermedius (Verrill, 1873). A, anterior end, dorsal view; B, anterior end, ventral view; C, anterior end, right lateral view; D, pygidium, left lateral view. A (USNM 1620973); B (USNM 1620993); C (USNM 1620974); D (USNM 1620967).

FIGURE 13. Scoloplos intermedius (Verrill, 1873). A, thoracic setiger 7, anterior view; B, anterior abdominal setiger, posterior view; C, middle abdominal setiger, posterior view; D–E, thoracic neuropodial uncini; F, furcate seta. (USNM 1620993).

FIGURE 14. Scoloplos intermedius (Verrill, 1873). Juveniles: A, 15-setiger juvenile; B, same, anterior end, ventral view; C, same posterior end right lateral view; D, thoracic neurosetae; E, 31-setiger pre-adult. A–C (USNM 1620947); D–E (USNM 16209478). All stained with Shirlastain A.