Inermosyllis pseudohaploides, Martín & Hutchings & Aguado, 2008

Martín, Guillermo San, Hutchings, Pat & Aguado, María Teresa, 2008, Syllinae (Polychaeta, Syllidae) from Australia. Part. 2. Genera Inermosyllis, Megasyllis n. gen., Opisthosyllis, and Trypanosyllis, Zootaxa 1840, pp. 1-53 : 3-5

Inermosyllis pseudohaploides n. sp.

Fig. 1 A–D

Material examined. Holotype ( AM W31384), paratype 1 ( AM W31385) AUSTRALIA: WESTERN AUS- TRALIA: Exmouth Gulf , Bundegi Reef, N end of beach, 21° 49' S, 114° 11' E, rocky rubble, brown algae with epiphytic growth, sticky sediment, 0–2 m, 4 Jan. 1984, coll. H.E. Stoddart. Paratype 1 ( AM W31386). NORTHERN TERRITORY: Darwin Harbour, East Point , 12° 24' 36" S, 130° 39' 57" E, dead coral rubble & algal washings, 7–10 m, 17 July 1993, coll. P.A. Hutchings.

Description. Holotype incomplete specimen, 15 mm long, 0.9 mm wide, with 44 chaetigers; paratypes also incomplete. Body elongate, slender, dark pigmented, with dorsal, rounded pale area on each segment, more marked after proventricular segments ( Fig. 1A, B). Prostomium oval to hexagonal, wider than long, with two pairs of eyes in trapezoidal arrangement. Antennae shorter than dorsal cirri, whip-shaped; median antenna inserted between posterior eyes, longer than prostomium and palps together, with about 25 articles; lateral antenna about half length of median antenna, similar in shape, inserted on anterior margin of prostomium, with about 19 articles. Palps broad, slightly longer than prostomium, fused for about half their length. Peristomium distinct, about half as long as following segments ( Fig. 1A). Dorsal tentacular cirri similarly shaped to median antenna, but longer, with about 27–30 articles; ventral tentacular cirri similar in length and shape to lateral antennae. Dorsal cirri longer than body width, slender, whip-shaped; those of chaetiger 1 distinctly longer than following ones, with about 45 articles; remaining dorsal cirri alternating in length, about 40–45 long and 20–25 short ones ( Fig. 1A, B); articles usually with 2 dark inclusions. Parapodial lobes conical, slightly bilobed distally. Ventral cirri digitiform. Compound chaetae on each parapodium, about 3–6, large, thick, apparently simple, but blades and shafts only partially fused, articulation still visible ( Fig. 1C); shafts short, markedly enlarged sub-distally, forming triangular fang; blades short, smooth, unidentate, more curved and shorter ventrally ( Fig. 1C), 30– 17 µm long. Chaetae similar on all parapodia. Three aciculae on anterior parapodia, 2 from midbody, 1 slender, almost straight, and 1 thicker, with distally oblique tip ( Fig. 1D). Capillary chaetae not seen. Pharynx through 5 segments. Proventricle slightly longer than pharynx, through 4–5 segments, with about 37 muscle cell rows. Pygidium lacking. Holotype mature female, with oocytes in posterior segments.

Remarks. All other described species of Inermosyllis differ from I. pseudohaploides n. sp., in having compound chaetae with shafts and blades well separated, not fused totally or partially. It resembles Haplosyllis in terms of general body shape, and possessing short, thick, apparently simple chaetae, but Inermosyllis pseudohaploides has compound chaetae, with both shafts and blades differentiated. While these chaetae are considered as compound they appear to represent an intermediate stage leading to fused blades and shafts ( Fig. 1C). Several recently described species of Haplosyllis seem to confirm the origin of their typical simple chaetae with the fusion of the blade and the shaft, these include: Haplosyllis anthogorgicola ( Martín et al. 2002) or H. loboi ( Paola et al., 2006) . The lack of a pharyngeal tooth has been confirmed after dissection of the pharynx of one of the paratypes of the new species.

Etymology. The specific name is derived from the Greek words pseudo, meaning false, and haplos, meaning simple, and refers to the presence of apparently simple chaetae, which are in fact compound.

Habitat. Found in amongst dead corals, rubble, algae, sediment; from intertidal to 10 m.

Distribution. Australia (Western Australia, Northern Territory).