Chaetozone donerae Blake 2022, new species

Chaetozone donerae new species

Figures 34–35

urn:lsid:zoobank.org:act: 305F98A9-5EDF-43A5-9BE3-CF10D2A1CE7A

Chaetozone sp. A: Maciolek-Blake et al. 1985: B-5 (in part).

Material examined. (87 specimens) Off Massachusetts, Georges Bank, MMS Benthic Infauna Monitoring Program, coll. G.W. Hampson, Chief Scientist: Sta. 2: Cruise M-2, Rep. 1, 14 Nov 1981, 40°59.2′N, 66°55.9′W, 70 m, holotype (USNM 1661219); Rep. 3, 14, 7 paratypes (USNM 1661220); Cruise M-3, Rep. 5, 18 Feb 1982, 40°59.2′N, 66°56.0′W, 73 m, 1 paratype (USNM 1661221); Rep. 6 (2, USNM 1661222); Cruise M-4, Rep. 1, 12 May 1982, 40°59.1′N, 66°55.9′W, 66 m (2, USNM 1661223); Rep. 6 (2, USNM 1661224); Cruise M-5, Rep. 1, 22 Jul 1982, 40°59.0′N, 66°55.8′W, 66 m, SEM stub 1 (1, USNM 1661225), SEM stub 2 (1, USNM 1661226) (7, USNM 1661227); Cruise M-7, Rep. 1, 07 Feb 1983, 40°59.2′N, 66°55.9′W, 71 m (6, USNM 1661228); Rep. 3, 9 paratypes (USNM 1661229); Rep. 4, 1 paratype (USNM 1661230); Rep. 6 (2, USNM 1661231); Cruise M-8, Rep. 1, 15 May 1983, 40°59.3′N, 66°55.9′W, 73 m, 2 paratypes (USNM 1661232); Rep. 3 (3, USNM 1661233); Rep. 4 (11, USNM 1661234); Rep. 6 (6, USNM 1661235); Cruise M-9, Rep. 1, 14 Jul 1983, 41°13.0′N, 66°55.8′W, 79 m, 2 paratypes (USNM 16612236); Rep. 3, 3 paratypes (USNM 1661237); Cruise M-10, Rep. 1, 15 Nov 1983, 41°13.0′N, 66°55.8′W, 79 m, 4 paratypes (USNM 1661238); Rep. 3 (1, USNM 1661239). Cruise M-11, Rep. 4, 03 Feb 1984, 40°59.0′N, 66°55.8′W, 79 m (3, USNM 1661240); Cruise M-12, Rep. 1 04 Jun 1984, 40°59.0′N, 66°55.8′W, 79 m (4, USNM 1661241). Sta. 5-29: Cruise M1, Rep. 2, Jul 1981, 40°39.4′N, 67°46.9′W, 82 m, 1 paratype (USNM 1661242); Rep. 3, 1 paratype (USNM 1661243).— Massachusetts Bay, MWRA Harbor and Outfall Monitoring Program: 1995 August Survey, Sta. NF-17: Rep. 1, Aug 1995, 42°22.88′N, 70°48.89′W, 29 m (4, MCZ 161944); Rep. 2 (31, MCZ 161945). 1997 August Survey, Sta. NF-17: Rep. 2, Aug 1997, 42°22.88′N, 70°48.89′W, 29 m (5, MCZ 161946. — Massachusetts, off Gloucester Harbor, coll. B.J. Dinkins, Sep 2009, 42°34.25′N, 70°70.65′W, 30.5 m, (3, MCZ 161947).

Description. A moderate sized species; holotype complete, 7.5 mm long, 0.5 mm wide across anterior segments with ca. 98 setigers (USNM 16612220); some complete paratypes larger, up to 13 mm long and 0.8 mm wide across anterior setigers, with ca. 95–100 setigers (USNM 16612236). Body relatively thick, widest in anterior half then gradually tapering to posterior end. Segments narrow, crowded along entire body; anterior and middle setigers short, ca. nine times wider than long. A narrow groove present along dorsal midline through middle segments (Fig. 34A); shallow ventral groove present along most of body. Posterior setigers with reduced cinctures leaving dorsal gap between notopodia and wide ventral gap between neuropodia (Fig. 35E). Color in alcohol light tan.

Pre-setiger region relatively long, about as long as first eight setigers (Fig. 34A). Prostomium triangular, tapering to narrow apex (Figs. 34A, 35A–B); eyespots absent; nuchal organs narrow slits on posterior lateral margins. Peristomium with two rings, with lateral groove not crossing dorsum (Fig. 34A); first ring narrowest, sometimes more swollen than second, both with low dorsal crest extending partially over setiger 1 mid-dorsally (Fig. 34A); dorsal tentacles arising from posterior margin (Figs. 34A, 35B). First branchiae on peristomium lateral to dorsal tentacles; second branchiae on setiger 1, dorsal to notosetae (Fig. 34A); subsequent branchiae in similar position. Branchiae long, numerous in anterior setigers, not as dense posteriorly (Fig. 35A–B), mostly absent in posterior setigers (Fig. 35A).

Parapodia of anterior and middle segments with parapodia formed into distinct lateral ridges from which setae arise; noto- and neuropodia close to one another. Setiger 1 and thoracic segments with 10–12 capillaries in notopodia and neuropodia; capillaries mostly of moderate size; long, natatory-like capillaries absent. Acicular spines first present in holotype from setiger 60–64 in notopodia and setiger 50–54 in neuropodia; spines 1–2 at first, increasing posteriorly into partial cinctures with 4–5 spines in notopodia and 5–6 in neuropodia or up to 9–11 spines on a side producing partial cinctures with wide dorsal and ventral gaps between notopodia dorsally and neuropodia ventrally (Fig. 35E). Spines distinctly curved, with basal manubrium, tapering to narrow tip (Fig. 35E–F); some spines with groove along one edge (Fig. 35G); spines alternating with capillaries up to three times longer than spines (Fig. 35E).

Body narrowing in last few segments; anus surrounded by 6–8 narrow lobes (Figs. 34B, 35D; pygidium terminating in semicircular disk bearing numerous glandular cells (Figs. 34B, 35D).

Methyl green staining. Body stains lightly with MG concentrated on laterally positioned parapodia, most strongly in posterior setigers where brightly stained parapodia contrast with lighter body.

Remarks. Locally, Chaetozone donerae n. sp. from Georges Bank is most similar to C. diodonta with which it may occur. The two species both exhibit reduced cinctures of acicular spines with distinct dorsal and ventral gaps, but differ in several respects. Chaetozone diodonta has three distinct peristomial rings instead of two, and has both bidentate and unidentate acicular spines in posterior neuropodia instead of only unidentate hooks. In addition, C. donerae n. sp. has fewer spines in posterior cinctures with 9–11 spines on a side producing a wider dorsal gap between the notopodia; C. diodonta has up to 13 spines on a side.

Globally, Chaetozone donerae n. sp. is most similar to Chaetozone christiei Chambers, 2000 from British waters off Northumberland on the North Sea and along the English Channel where the species occurs in intertidal and shallow subtidal depths. Both C. donerae n. sp. and C. christiei have reduced cinctures of acicular spines in posterior parapodia leaving wide dorsal and ventral gaps between spines on both sides of the body. Chaetozone christiei (ca. 12 mm long with 110 setigers) and C. donerae n. sp. (ca. 13 mm long with 98 setigers) are of a similar size and shape and both are reported to have a ventral groove along most of the body. Chaetozone donerae n. sp. has two peristomial rings with a dorsal crest, whereas C. christiei has three peristomial rings and no dorsal crest. The dorsal tentacles of both species arise from the posterior margin of the peristomium. The first branchiae arise lateral and slightly posterior to the dorsal tentacles on C. donerae n. sp., whereas the first pair of branchiae of C. christiei occur on setiger 1. Chaetozone donerae n. sp. has up to 4–5 spines in notopodia and 5–6 in neuropodia or 9–11 on side, whereas C. christiei is reported to have up to 4–5 spines in both noto- and neuropodia or 8–10 spines on a side. The MG staining pattern was not reported for C. christiei.

Biology. On Georges Bank, Chaetozone donerae n. sp. occurred at Stations 2 and 5 at depths of 65– 80 m. Both stations mainly consist of coarse to fine sands (96–99%) with only trace amounts of silt (1–4%) (Maciolek et al. 1985). In contrast, C. diodonta occurred along the deeper 140–150 m isobaths, also with a high sand content (~95%), but with the coarse sand (~45%) fractions being higher than at the shallower sites (~20%) where C. donerae n. sp. occurred.

Chaetozone donerae n. sp. (as C. sp. A), although consistently present, was not among abundant species at the sites on Georges Bank where it occurred. Station 2 was typically dominated by several syllid polychaetes and the sand dollar Echinarachnius parma (Lamarck, 1816) (Maciolek et al. 1985). The species was also collected at 30 m sites in Massachusetts Bay and off Gloucester Harbor.

Etymology. This species is named for Ms. Stacy A. Doner Tewari, my former graduate student and colleague, in recognition of her work on benthic ecology and expertise with the systematics of Cirratulidae and other polychaetes.

Distribution. Off New England, Georges Bank, 65–82 m; off Gloucester, Harbor, 30 m; Massachusetts Bay, 29 m.