Hyalopomatus macintoshi (Gravier 1911)

Hyalopomatus macintoshi (Gravier, 1911)

Cystopomatus macintoshi Gravier, 1911a, pp. 315–316; 1911b, pp. 149–152. pl. 11: figs. 145–152.—Fauvel, 1936, pp. 39–40—Hartman, 1959, p. 572; 1966, pp. 128–129, 131, pl. 43: figs. 8–11.

MATERIAL EXAMINED.—West coast of Antarctic Peninsula: 1 spec., incomplete, Second French Antarctic Expedition (“Pourquoi-Pas”), 1908–1910 (MNHN). Bellingshausen Sea: 2 spec., incomplete, “Belgica” Expedition, 1897–1899 (IRSN).

DESCRIPTION.—Tube white, smooth and of circular cross section, more or less curved or straight and erect distally for some length. The whole length of the tube may attain 50 mm, its diameter 750 μ. Length of the animal up to 12 mm, including 4 mm for the gill tuft. About 40 abdominal segments. Collar large and divided into 3 lobes, the laterodorsal ones continued into short thoracic membranes ending at the limit of segments 2 and 3. Gill tuft composed of about 12 filaments on each side. Operculum a transparent almost globular vesicle fixed to a very thin, smooth, non-pinnate opercular stalk. The specimens studied are in too poor condition to show the insertion of the opercular stalk or the existence of a gill membrane.

First thoracic segment with capillary setae and stronger special setae, with a distal limbate zone and a proximal more coarsely denticulate wing, the two zones not well separated. The following 5 segments with only two types of setae: capillary and limbate; no thoracic sickle-setae. The posterior abdominal setae are long and almost capillary, with their distal tips (about one-fifteenth of their length) slightly geniculate. The setae of the more anterior segments are shorter and more geniculate (geniculate part corresponding to about one-tenth of their whole length). Thoracic uncini rasp-shaped with 2 or 3 teeth in transverse rows, in lateral view with about 20 teeth; the most anterior tooth large and bifurcate. The number of thoracic neuropodial uncini decreases in the posterior segments: there may be 110 in the second setigerous segment but only 80 in one row in segment 6. Abdominal notopodial uncini in rows of 20 to 30, rasp-shaped, with a more curved profile than the rather rectangular thoracic uncini and with more teeth in transverse rows.

DISTRIBUTION.—The type specimens collected by the Second French Antarctic Expedition (“Pourquoi-Pas,” 1908–1910) are from Peterman Island off the west coast of Antarctic Peninsula (about 67°S, 69°W, no indication of depth, mixed with Serpula vermicularis var. narconensis). The specimens from the “Belgica” Expedition are from a large zone in the Bellingshausen Sea (between 80°48′W and 87°37′W, 70°00′S and 71°19′S, in about 400–500 m). No other records are known.