Ilyphagus coronatus Monro, 1939

Salazar-Vallejo, Sergio I., 2012, Revision of Ilyphagus Chamberlin, 1919 (Polychaeta, Flabelligeridae), ZooKeys 190, pp. 1-19 : 8-9

Ilyphagus coronatus Monro, 1939 Figure 3

Ilyphagus coronatus Monro, 1939:130-131, fig. 19; Hartman 1966:41, pl. 12, Figs 4-6, Hartman 1967:127; Rozbaczylo 1985:159-160.

Type material.

Antarctic Ocean. Three syntypes of Ilyphagus coronatus Monro, 1939 (NHML-1941.3.3.99-100), off Princess Elizabeth Land, Stat. 29 (66°28'S, 72°41'E), 1266 m (syntypes complete, one broken in two pieces; the largest one was already dissected by Monro; 23-40 mm long, 5-9 mm wide, cephalic cage (broken) 12-21 mm long, 23-25 chaetigers).

Additional material.

Three specimens (USNM-56696, LACM-AHF unnumb.), R/V Eltanin Cruise, Stat. 138 (62°00'S, 61°09'W), 1437 m, 8 Aug. 1962 (slightly damaged; larger specimen (USNM) 52 mm long, 8 mm wide, cephalic cage broken 10 mm long, 22 chaetigers). Three fragments (USNM-56697), R/V Eltanin Cruise, Stat. 480 (58°06'S, 44°56'W), 2800 m, 15 Feb. 1963 (anterior fragment, 20 mm long, 5.5 mm wide, 13 chaetigers). Two specimens (ZMH-24530), Cruise ANT/ XV-3, R/V PolarStern, South of Vestkapp, St. 48-088 (73°28.5'S, 22°30.0'W), 1681 m, 4 Feb. 1998, B. Hilbig, coll. (42-45 mm long, 10-11 mm wide, cephalic cage 7-18 mm long, 24-25 chaetigers).

Description.

Largest syntype cylindrical, globose, posteriorly rounded (Fig. 3A); 48 mm long, 8 mm wide, remaining cephalic cage chaetae broken, 6 mm long, 24 chaetigers. Body surface densely papillated (Fig. 3B); papillae long, filiform, tapering, or slightly capitate, with many adherent sediment particles over its basal and medial regions.

Anterior end not exposed; observed by dissection of anterior end in anterior fragment of syntypes, or other non-type specimens (USNM-56698, USNM-56696). Prostomium low cone, without eyes. No caruncle (Fig. 3D). Palps massive, as long as branchiae; palp lobes low. Lateral and dorsal lips fused; ventral lip reduced. Branchiae digitate, 14 filaments, arranged in three irregular rows: superior one with 4 filaments, two lateral groups medially placed each with 3 filaments, and two lateral basal ones with 2 filaments each; largest branchiae as long as palps.

Cephalic cage chaetae mostly broken; size relationships with body length or width unknown; syntypes with chaetae at least as long as body width and one with chaetae almost as long as body length; one very long chaetae straight, with successive constrictions but anchylosed articles perpendicular to the main shaft. Chaetiger 1 involved in cephalic cage; notochaetae of chaetiger 2 very long, thin. Chaetiger 1 with 8 notochaetae in transverse short dorsal row; neurochaetae in C-pattern, opening towards the posterior end, looking like two series, with 8 neurochaetae.

Anterior dorsal margin of first chaetiger papillated, projected anteriorly, conical, continued with the longitudinal body opening; anterior chaetigers without especially long papillae. Chaetigers 1-3 of about same length. Chaetal transition from cephalic cage to body chaetae abrupt; aristate neurospines from chaetiger 2. Gonopodial lobes in chaetiger 5, as long as neuropodial width (Fig. 3C), dark in syntypes (paler in other specimens), digitate.

Parapodial development difficult to detect due to papillae cover (USNM-56698); notopodia not detected; chaetae stem from long, rounded neuropodial lobes. Parapodia lateral; median neuropodia ventrolateral. Noto- and neuropodia close to each other.

Median notochaetae arranged in short longitudinal rows, as long as half body width, about 2 per ramus; all notochaetae multiarticulated capillaries, articles very short along most of the chaeta, distally difficult to see (Fig. 3E), hyaline. Neurochaetae anchylosed aristate spines from chaetiger 2, arranged in transverse rows, 4-5 or up to 7-8 per ramus (Fig. 5F). Both noto- and neurochaetae (USNM-56697) with distal portions rough; fibers are individually and irregularly broken off from the main axis (Fig. 3G), not hirsute.

Posterior end (USNM-56696) rounded, pygidium with anus terminal, without cirri.

Remarks.

Ilyphagus coronatus Monro, 1939 can be separated from other cigar-shaped species because of the relative size of body papillae, which appear pilose, and because its neurochaetae, despite possibly appearing hirsute due to fracture, are mostly smooth.

Distribution.

Only known from two localities around Antarctica, in 1200-3500 m.