Trochochaeta watsoni (Fauvel 1916)

Trochochaeta watsoni (Fauvel)

Disoma watsoni Fauvel, 1916:1, fig. 1a–i; 1932b:28, pl. 1: figs. 8–11.—Belloc, 1953:6.—Hartman, 1965:159, pl. 32: figs, c–f.—Hartman and Fauchald, 1971:107.

Trochochaeta watsoni.—Pettibone, 1963b:315, fig. 83h–k.

MATERIAL EXAMINED.—New England: 41°13′N, 66°W, 1657 m, blue mud, Albatross sta. 2076, 4 September 1883, 2 anterior fragments (USNM 28953). 40°16′N, 67°05′W, 2359 m, Albatross sta. 2084, 5 September 1883, 12 anterior fragments (USNM 51929).

DESCRIPTION.—Length of incomplete specimen of 25 segments (USNM 51929) 5 mm, width 2 mm, including setae. Prostomium (Figure 4a,b) elongate, fusiform, wide and rounded or slightly bilobed anteriorly, with longitudinal crest and small conical median antenna on posterior part (keeled, according to Fauvel), with nuchal crest extending posteriorly on first segment; without eyes. Tentacular palps missing but oval bases visible between prostomium and parapodia of first segment.

Biramous parapodia of anterior four segments of thoracic region considerably modified, differing from one another (Figure 4a–k). Parapodia of first segment shifted dorsally and directed anteriorly, partly enclosing prostomium; notopodial and neuropodial lobes with short and longer, slender, smooth, capillary setae forming spreading bundles, notosetae fewer and shorter than neurosetae; notopodial postsetal lobes elongate, lanceolate (Figure 4a–d). Parapodia of second segment shifted ventrally, lateral to mouth; notosetae slender, capillary, smooth, forming spreading bundles (Figure 4f); neurosetae stouter than notosetae, forming fan-shaped bundles, anterior row of stouter and posterior row of slightly more slender ones, both types slightly limbate, dotted and ending in curved fine tips (Figure 4g; stouter ones referred to as subacicular by Fauvel); notopodial and neuropodial postsetal lobes subcorneal, latter shorter than former (Figure 4a,b,e). Third segment with notopodia similar to those of second segment; neuropodial setal lobes low, wide, with fan-shaped bundles of neurosetae, anterior row of 4–6 stout acicular spines with blunt tips and posterior row of slender, curved neurosetae with fine tips (Figure 4i); postsetal lobes subglobular, shorter than notopodial (Figure 4a,b,h). Fourth segment with similar low, rounded notopodial and neuropodial lobes; notosetae slender, smooth capillary, forming spreading bundles; postsetal notopodial lobes thick, fleshy, and subconical; neurosetae shorter and slightly stouter than notosetae, slightly limbate, tapering rather abruptly to capillary tips (Figure 4k); postsetal neuropodial lobes thick, fleshy, and subrectangular (Figure 4a,b,j).

Following 7 thoracic segments (segments 5–11) similar, with lateral biramous parapodia (Figures 4a,b, 5a–h). Notopodial setal lobes low, rounded, with slender, slightly limbate, delicately frayed, capillary notosetae; postsetal lobes thick, fleshy, subconical, becoming more slender on segments 8–10 and lacking on segment 11, associated with smaller bundles of notosetae (Figure 5h). Neuropodial setal lobes low, rounded, with neurosetae of 2 kinds: central group of stout, curved, broadly limbate, more or less frayed, with erect fine tips; upper, posterior and lower ones longer, slender, slightly limbate, delicately frayed, capillary (Figure 5c); postsetal lobes thick, fleshy, and subconical to oval.

Abdominal region (Figure 5i–k) beginning on segment 12, with notopodia lacking; neurosetae of 2 kinds: slightly stouter, tapering rather abruptly to capillary tips, and more slender, slightly limbate, frayed, capillary (Figure 5k); postsetal lobes subconical, continuing posteriorly as delicate, slightly undulate flanges. Posterior abdominal region missing.

DISTRIBUTION.—North Atlantic, off Nova Scotia to off New England, in 530 to 3753 m.

lower St. Lawrence estuary to off Massachusetts

bathyal of the Gulf and estuary