Paradiopatra imajimai n. sp.

Figures 3, 4; Table 2

Material examined. Type material—SLOPE 67: holotype (MV F189431); 12 paratypes (MV F189432); 2 paratypes (AM W43551), 2 paratypes, mounted for SEM (AM W43551.001).

Non-type material—SLOPE 25: 2 specimens (MV F189433); SLOPE 27: 1 specimen (MV F189434); SLOPE 53: 8 specimens (MV F189435); SLOPE 81: 3 specimens (MV F189436).

Type locality. Pacific Ocean, Bass Strait, off eastern Victoria, 38º23.95’S, 149º17.02’E, 1277 m.

Diagnosis. Ovoid frontal lips; ceratophores without lateral projections; peristomial cirri present; first three pairs of parapodia with pseudocompound, weakly bidentate falcigers with moderately long pointed hoods, shafts with spines in rows and scattered, appendages smooth; subacicular hooks equal, starting from chaetiger 9; branchiae absent; very large protomandibles.

Description. All examined specimens lacking posterior ends. Length of holotype 16 mm for 41 chaetigers, width 0.9 mm (at chaetiger 10, excluding parapodia); paratypes ranging from 3.5–17 mm long (16–40 chaetigers), 0.4–1.0 mm wide. Non-type material ranging from 0.4–0.8 mm in width. Alcohol stored specimens overall creamcoloured, lacking colour pattern.

Prostomium anteriorly rounded, wider than long, with paired ovoid frontal lips, positioned closely together (Fig. 3 A–C). Ceratostyles slender; palps of holotype reaching chaetiger 1 (paratypes: peristomium–chaetiger 1); lateral antennae reaching chaetiger 3 (chaetigers 3–5); median antenna reaching chaetiger 2 (chaetigers 1–3). Ceratophores with well developed annulation, lacking lateral projections; ceratophores of lateral antennae with 5 (4–6) rings, median antennae with 4 (4–5) rings; terminal ring twice as long as proximal ones. Nuchal grooves weakly curved, medially widely separated. Eyes absent. Peristomium shorter than first chaetiger. Peristomial cirri short and tapering, about half as long as peristomium, inserted subdistally (Fig. 3 C).

First three pairs of parapodia modified, projecting anterolaterally, directed slightly ventrally (Fig. 4 A, B). Prechaetal lobes rounded on all parapodia; postchaetal lobes triangular to subulate in first chaetigers, decreasing rapidly in size, absent from chaetiger 9 (8–9). Dorsal cirri long and slender in anterior parapodia, becoming very short in median region. Ventral cirri subulate on first three chaetigers, third one shorter than first two, replaced by ovoid ventral lateral pads from chaetiger 4 (Fig. 3 B).

Parapodia supported by three aciculae projecting about half as far as falcigers and limbate chaetae from prechaetal lobe (Fig. 4 A, B). First three pairs of parapodia with dorsal fascicle of one simple limbate chaeta and ventral fascicle of 4–6 weakly bidentate pseudocompound falcigers with moderately long pointed hoods (Fig. 4 C); shafts of falcigers with scattered small spines and rows of spines (Fig. 3 D), appendages smooth (Fig. 3 E). Two fascicles of simple limbate chaetae starting from chaetiger 4. Ventral fascicle of limbate chaetae replaced by paired, bidentate subacicular hooks from chaetiger 9 (Fig. 3 F), hooks about equal in length and thickness. Pectinate chaetae (Fig. 3 G) slightly oblique with 13–15 teeth. Branchiae absent. Posterior end and tube unknown.

Mandibles (Fig. 4 D) slender, with high calcareous cutting plates and remarkably large protomandibles visible through cutting plates. Maxillae (Fig. 4 E) delicate, hardly sclerotised. Maxillary formula (based on one paratype): MI = 1 + 1; MII = 8 + 8; MIII = 6 + 0; MIV = 6 +7; MV = 1 + 1.

Remarks. Paradiopatra imajimai n. sp., resembles P. fragosa (Ehlers, 1887) and P. o k a i Imajima, 1999 in having bidentate falcigers, three pairs of modified parapodia, subacicular hooks starting from chaetigers 9, and lacking branchiae. It can be distinguished from both species by having much slenderer antennal styles, longer, slenderer dorsal cirri and weakly rather than clearly bidentate falcigers, and furthermore from P. fragosa in having ceratophores with a much longer terminal ring and ovoid rather than globular frontal lips, and from P. o k a i in lacking eyes rather than having them.

Etymology. It is a pleasure to dedicate this new species to Dr. Minoru Imajima in recognition of his contributions to the study of polychaetes.

Distribution. Paradiopatra imajimai n. sp., was collected in all three transects: south of Sydney, NSW, off eastern Victoria in Bass Strait, and off Freycinet Peninsula, eastern Tasmania, in 996–1850 m.