Leodamas cuneatus Blake 2021, new species

Leodamas cuneatus new species

Figures 28–29

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Leodamas sp. 1: Maciolek et al. 1987b: D-3.

Material examined. Off New England, US North Atlantic ACSAR Program, coll. G.W. Hampson, Chief Scientist. Sta. 5: Cruise NA-2, Rep. 1, 20 Apr 1985, 40°05.07′N, 67°29.78′W, 2060 m, holotype (USNM 1622267). Sta. 11: Cruise NA-1, 3 Dec 1984, Rep. 2, 40°01.29′N, 70°55.04′W, 255 m, 2 paratypes (USNM 1622268).— Off New Jersey and Delaware, U.S. Mid-Atlantic ACSAR Program, coll. R.M. Petrecca, Chief Scientist. Sta. 11: Cruise Mid-3, Rep. 2, 04 Dec 1984, 38°40.14′N, 72°56.31′W, 1520 m (1, USNM 1622269).

Description. A moderately sized species, holotype nearly complete with 90 setigers, about 30 mm long and 1.4 mm across thorax; larger of two juvenile paratypes (USNM 1622268) complete with 39 setigers, 3.7 mm long, 0.43 mm wide across thorax. Thorax of holotype with 14 setigers and branchiae from setiger 5; larger paratype with eight thoracic setigers and branchiae from setiger 5. Thoracic segments slightly wider than abdominal segments. Thoracic segments flattened dorsally and ventrally; abdominal segments also flattened dorsally, but rounded ventrally, with parapodia shifted dorsally. Thoracic setigers short, about 5 times wider than long; individual thoracic segments

separated dorsally by prominent intersegmental ridge (Fig. 28A), ridges less prominent ventrally; in abdominal segments intersegmental area expanding across segments and with parapodial ridge individual segments visibly biannulate. Color in alcohol opaque white.

Pre-setiger region triangular, wedge-shaped, merged dorsally with setiger 1 (Fig. 28 A–B). Prostomium short, broadly triangular, narrowing to pointed tip (Fig. 28 A–B); nuchal organs not observed; eyespots absent. Peristomium smooth dorsally, not divided by annular rings; ventrally surrounding mouth and forming upper and lower lips (Fig. 28B); upper lip a smooth circular ring; ventral lip with about 10 short lobes; proboscis partially everted on holotype. Peristomium thickened on ventral side posterior to mouth, extending over setiger 1 (Fig. 28B).

Thoracic notopodia with single long, tapering digitiform postsetal lobe (Fig. 29A). Thoracic neuropodia enlarged, rounded, with digitiform postsetal lobe arising from middle of rounded neuropodial base, lobe shorter than that of notopodium (Fig. 29A). Transition to abdominal segments identified by narrowing and elongation of neuropodium and fewer capillary neurosetae. Abdominal notopodia similar to those of thorax with long, digitiform postsetal lobe (Fig. 29 C–D). Abdominal neuropodia with long, narrow subterminal lateral digitiform lobe, continuing to near posterior end (Fig. 29 C–D). Interramal cirrus absent, but low thickened ridge present between noto- and neuropodia of anterior abdominal setigers.

Branchiae from setiger 5, with first pair short, widest basally (Fig. 28A); subsequent thoracic and anterior abdominal branchiae elongate, widest basally, tapering to narrow apex (Figs. 28A, 29A, C–D); middle and posterior abdominal branchiae more or less narrow along entire length; all branchiae with lateral cilia along at least half their length.

Thoracic notosetae all camerated capillaries; first 2–3 setigers with 15–20 notosetae, increasing to 30–40 over subsequent thoracic segments, then reduced to 2–3 by setiger 14. Thoracic neuropodia with up to 20 uncini or spines accompanied by capillaries arising in 3–4 groups. Uncini arranged in up to four vertical rows (Fig. 29B) with 8–9 spines of first row largest (Fig. 28 D–F), with weakly developed ridges along one edge (Fig. 28D) or entirely smooth (28E–F); spines of second and third rows smaller, with distinct ribs along one edge and subterminal notch (Fig. 28G); spines of last row narrowest with distinct ribs along one edge (Fig. 28H); thoracic neuropodial capillaries arranged in 3–4 poorly defined groups. Abdominal notosetae including camerated capillaries, 1–3 furcate setae, and a single large acicular spine (Fig. 29 C–D insets); furcate setae with unequal tynes, with narrow tips and with thin fibrils along each edge extending inward toward opposite tyne (Fig. 28I). Abdominal neurosetae including capillaries and 1–2 emerging acicular spines (Fig. 29 C–D insets); capillaries numbering 7–10 at first, reduced to 3–4 in middle and posterior setigers. Flail setae not observed.

Pygidium rounded, with two thick anal cirri, only observed on both juvenile paratypes (Fig. 28C).

Remarks. Leodamas cuneatus n. sp. is a distinctive species in having a broad wedge-shaped pre-setiger region that gives the worm the appearance of having a foreshortened anterior end; although short, the prostomium is clearly pointed, not blunt on the tip. In addition, there is a range of large to small spines with and without ribs along the shaft in the thoracic neuropodia. Species of Leodamas, by definition, typically have well-developed emergent acicular spines in abdominal neuropodia. However, in L. cuneatus n. sp. there are also emergent spines in abdominal notopodia. Based on morphology, this species has no close relatives.

Etymology. The epithet cuneatus is derived from cuneus, Latin for wedge, in reference to the unusual wedgeshaped pre-setiger region of this species.

Distribution. U.S. Atlantic continental slope, New England to off Delaware, in slope depths, 255–2060 m.