Questa trifurcata (Hobson, 1970)

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 : 110-113

Questa trifurcata (Hobson, 1970)

Figures 55–56

Novaquesta trifurcata Hobson 1970: 191–194 , Fig. 1 ; Giere & Riser 1981: 95–103, Figs. 1–5 ; Taylor & Gathof 1984: 3-4 to 3-5, Fig. 3-4 ; Jamieson & Webb 1984: 30–31.

Questa trifurcata: Giere & Erséus 1998: 345–360 , Figs. 1G , 2 G–H, 3H.

Material examined. (31 specimens) Northeastern USA, off New England, Georges Bank, Benthic Infauna Monitoring Program (1981–1984), coll. G.W. Hampson, Chief Scientist. Sta. 2: Cruise M-1, Rep. 2, Jul 1981, 40°59.0′N, 66°55.8′W, 70 m (2, USNM 1622538 ) ; Cruise M-11, Rep. 5, 03 Feb 1984, 40°59.0′N, 66°55.8′W, 79 m (4, USNM 1622539 ) ; Rep. 6, 03 Feb. 1984, 40°59.0′N, 66°55.8′W, 79 m (2, USNM 1622540 ) . Sta. 13: Cruise M-2, Rep. 6, 9 Nov. 1981, 40°29.5′N, 70°12.6′W, 60 m (1, USNM 1622541 ) . Sta. 5-3: Cruise M-4, Rep. 4, 14 May 1982, 40°39.8′N, 67°46.1′W, 84 m (1, USNM 1622542 ) . Sta. 5- 5: Cruise M-1, Rep. 1, Jul 1981, 40°39.3′N, 67°46.2′W, 70 m (1 ( USNM 1622543 ). Sta. 5-6: Cruise M-4, Rep. 3, 14 May 1982, 40°39.5′N, 67°45.4′W, 110 m (1, USNM 1622544 . Sta. 5-11: Cruise M-2, Rep. 1, 19 Nov 1981, 40°39.2′N, 67°46.6′W, 80 m (1, USNM 1622545 ).

Sta. 5-12: Cruise M-2, Rep. 1, 20 Nov 1981, 40°39.0′N, 67°46.1′W, 79 m (1, USNM 1622546 ) . Sta. 5-14: Cruise M-2, Rep. 2, 19 Nov 1981, 40°39.6′N, 67°44.4′W, 82 m (1, USNM 1622547 ) . Sta. 5-16: Cruise M-2, Rep. 2, 18 Nov 1981, 40°40.6′N, 67°46.1′W, 79 m (6, USNM 1622548 ) . Sta. 5-18: Cruise M-1, Rep. 1, Jul 1981, 40°39.6′N, 67°47.6′W, 80 m (5 USNM 1622549 ) ; Cruise M-2, Rep. 1, 18 Nov. 1981, 40°39.6′N, 67°46.3′W, 80 m (2, USNM 1622550 ) . Sta. 5-22: Cruise M-2, Rep. 3, 20 Nov 1981, 40°39.5′N, 67°43.3′W, 80 m (1, USNM 1622551 ) . Sta. 5-28: Cruise M-1, Rep. 2, Jul 1981, 40°39.5′N, 67°41.9′W, 80 m (2, USNM 1622553 ) ; Cruise M-2, 20 Nov 1981, 40°39.5′N, 67°43.3′W, 80 m (1, USNM 1622552 ) .

Description. A small, threadlike species, originally reported up to 4–6 mm long, and 0.3–0.4 mm wide and about 30 setigers (Hobson 1970). Giere & Riser (1981) recorded living specimens 9 mm long, 0.25 mm wide and 26–33 setigers. Present materials from Georges Bank up to 4.5 mm long, 0.2 mm wide, with 31 setigers. Body generally cylindrical in cross section throughout, widest in first 10–12 setigers, then narrowing posteriorly ( Fig. 56 A–B); no dorsal or ventral grooves or ridges along body. Anterior segments with 1–2 narrow intersegmental rings increasing to 5–6 in middle segments, decreasing posteriorly. Males with prominent pair of flaps forming a dorsal fold at about setigers 13–14 ( Fig. 56A, C ); females with ovaries and eggs in setigers 12–13. Color in alcohol opaque white; pink in life ( Giere & Riser 1981).

Pre-setiger region about as long as first 3–4 setigers. Prostomium weakly divided into a narrow conical anterior part, tapering to rounded apex and wider posterior part ( Fig. 55 A–B), with narrow, slit-like nuchal organs on posterior lateral margins. Peristomium with two narrow rings, relatively smooth dorsally ( Fig. 55A ); ventrally with mouth located on anterior ring and posterior margin of prostomium ( Fig. 55B ). Mouth with two rows of short lobes on posterior margin forming posterior lips; anterior part of mouth extending onto prostomium as narrow slit with a pair of lateral lobes ( Fig. 55B ).

Parapodia reduced to low mounds from which setae emerge, or setae emerging directly from body wall; no postsetal lobes or lamellae; branchiae entirely absent. Setae of each ramus including single bidentate hook arranged vis-à-vis with opposite and 2–3 serrated capillaries from setiger 1 ( Fig. 55G ); sometimes up to four capillaries present. Capillaries narrow, with short pointed barbs along one edge ( Fig. 55D inset); bidentate hooded hooks with geniculate shape, with main fang at right angle to shaft surmounted by pointed apical tooth; closely adhering hood or sheath extending from tip of main fang to shaft ( Fig. 55 D–E). One or two furcate setae present in notopodia of first 5–8 setigers; furcate setae with two subequal thick tynes and a single medial prong producing a tridentate appearance ( Fig. 55F ).

Pygidium with two thick lobes surrounding anal opening; anal cirri absent ( Figs. 55C , 56 A–B).

Remarks. Among ten known species of Questa , only four are reported to have furcate setae in the notopodia. Of these, Q. retrospermatica Giere et al., 2008 from Hawaii is the only species to have furcate setae with two long lateral tynes and two short medial tynes. Questa trifurcata , Q. riseri Giere & Erséus, 1998 from the Bermuda Islands, and Q. media Westheide, 1981 from the Galápagos Islands each have furcate setae with two long tynes and a single shorter medial prong producing a trifurcate or trident appearance. Questa trifurcata differs from both Q. riseri and Q. media in having no branchiae and no anal cirri instead of paired branchiae in posterior setigers and four anal cirri.

A detailed description of the internal anatomy of Q. trifurcata was provided by Giere & Riser (1981). This report largely focused on the unusual reproductive morphology summarized in the Genus Remarks (above). Most recent studies of Questa systematics have compared the internal morphology among species where available.

Reports of an additional tooth on the bidentate hooks ( Giere & Erséus 1998) appear to represent a thin extension of hood around main fang to upper surface ( Fig. 55E ).

Distribution. East coast of North America, Maine to New Jersey, intertidal and shallow subtidal to outer continental shelf depths on Georges Bank (60–110 m); Gulf of Mexico, off Florida, 37 m.

Figures

FIGURE 1. Leitoscoloplos acutus (Verrill, 1873). A, anterior end, dorsal view; B, anterior segments, ventral view; C, posterior end, dorsolateral view; D, middle thoracic setigers, posterior view; E, posterior abdominal setiger, anterior view; F, furcate seta. A, D–F (USNM 1620848); B (MCZ 161458); C (MCZ 161418).

FIGURE 2. Leitoscoloplos acutus (Verrill, 1873). A, anterior half of large specimen, dorsolateral view; B, middle thoracic setiger, anterior view; C, middle abdominal setiger, posterior view; D, fascicle of abdominal notosetae with capillaries and furcate seta; E, posterior setigers, left lateral view; F, posterior end, dorsolateral view. A, E (MCZ 161445); B (USNM 1620847); C–D (USNM 1620841); F (MCZ 161419). All stained with Shirlastain A.

FIGURE 3. Leitoscoloplos acutus (Verrill, 1873). Juveniles: A, 21 setigers; B, 26-setigers; C, 28 setigers; D, 28 setigers; E, 40 setigers; F, 48 setigers, anterior end. A–D (MCZ 161432); E (MCZ 161464); F (MCZ 161511). All stained with Shirlastain A.

FIGURE 4. Leitoscoloplos fragilis (Verrill, 1873). (MCZ 161582): A, anterior end, dorsal view; B, anterior end, ventral view; C, thoracic setiger 11, posterior view; D, thoracic setiger 16, posterior view; E, setiger 25, posterior view; F, posterior setiger, posterior view.

FIGURE 55. Questa trifurcata (Hobson, 1971). A, anterior end, dorsal view; B, anterior end, ventral view; C, posterior end, dorsal view; D, neuropodial hooked seta with capillaries (inset not to scale); E, notopodial furcate seta; G, middle body parapodium with hooks and capillaries. A, C, D–G (USNM 1622548); B (USNM 1622540).

FIGURE 56. Questa trifurcata (Hobson, 1971). (USNM 1622549): A. entire worm, dorsolateral view; B, smaller specimen, dorsolateral view; C, dorsal fold of mid-body segments of male.A–C All stained with Shirlastain A.