Ilyphagus hirsutus Monro, 1937

Salazar-Vallejo, Sergio I., 2012, Revision of Ilyphagus Chamberlin, 1919 (Polychaeta, Flabelligeridae), ZooKeys 190, pp. 1-19 : 9

Ilyphagus hirsutus Monro, 1937 Figure 4

Ilyphagus hirsutus Monro, 1937:304-305, textfig. 22.

Type material.

Central Indian Ocean, South Arabian Sea. Holotype (NHML-1937.9.2.455), John Murray Expedition, H.E.M.S. Mabahiss, Stat. 133(01°25'54"S, 66°34'12"E → 01°19'42"S, 66°35'18"E), 15 Feb. 1934, 3385 m (station data after Sewell 1935).

Description.

Holotype pale, globose, widened in the posterior half (Fig. 4A, B); 37 mm long, 10 mm wide, cephalic cage chaetae broken, 19 chaetigers. Body surface densely papillated, with abundant fine sediment particles; papillae long, cylindrical, each covered by a thin layer of fine sediment particles.

Cephalic hood not exposed; specimen not dissected to avoid further damage. Cephalic cage chaetae length unknown. Chaetiger 1 involved in the cephalic cage; chaetae arranged in short rows, notochaetae dorsal, 5-7 per bundle (bases damaged, difficult to count); neurochaetae ventrolateral, 3-4 per bundle.

Anterior dorsal margin of first chaetiger projected anteriorly (Fig. 4C), large rounded lobe, bent ventrally. Anterior chaetigers without especially long papillae. Chaetiger 1 largest, chaetigers 2-3 of about the same size. Chaetal transition from cephalic cage to body chaetae abrupt; chaetiger 2 with shorter neurochaetae, directed ventrolaterally. Gonopodial lobes present in chaetiger 5, low rounded dark, displaced ventrally, and positioned towards posterior segmental margin.

Parapodia lateral; median neuropodia ventrolateral. Notopodia scarcely noticed; neuropodia thick low muscular lobes, without especially longer papillae. Noto- and neuropodia close to each other.

Median notochaetae mostly broken; one anterior notopodia with 3 notochaetae, arranged in a tuft, median notochaetae as long as 1/5 body width, about 3 per fascicle; all notochaetae multiarticulated capillaries, articles short basally, medium-sized medially, long distally (Fig. 4D). Neurochaetae probably multiarticulated capillaries in chaetiger 1; from chaetiger 2, anchylosed aristate spines (Fig. 4E), arranged in transverse rows, in two series, with about 8 chaetae per fascicle. Neurospines basally cylindrical with very short articles, medially flat, distally tapering with slightly longer articles; neurospines basally smooth, subdistally and distally with fibers separated from the main stem, giving hirsute appearance to chaetal surface (Fig. 4F).

Posterior end globose, damaged; pygidium with anus terminal, without anal cirri.

Remarks.

Ilyphagus hirsutus Monro, 1937 resembles Ilyphagus bythincola because of their dense coverage with fine, long papillae. They differ because Ilyphagus hirsutus has a projected lobe in the first neuropodia, which is not present in Ilyphagus bythincola , and because the neurochaetae of the former are markedly hirsute distally, whereas those in Ilyphagus bythincola are either distally hyaline or slightly hirsute.

Distribution.

Originally described from the Central Indian Ocean, in deep water (3385 m); it has not been recorded since.