Paradiopatra longicappa, Paxton, Hannelore & Budaeva, Nataliya, 2013

Paxton, Hannelore & Budaeva, Nataliya, 2013, Paradiopatra (Annelida: Onuphidae) from eastern Australian waters, with the description of six new species, Zootaxa 3686 (2), pp. 140-164 : 148-150

Paradiopatra longicappa n. sp.

Figures 5 , 6 ; Table 2

Material examined. Type material—SLOPE 39: holotype (MV F192518); 18 paratypes (MV F192519); 4 paratypes (AM W43546); 1 paratype, mounted for SEM (AM W43546.001).

Non-type material—SLOPE 40: 20 specimens (MV F192520), SLOPE 46: 32 specimens (MV F192521); SLOPE 47: 3 specimens (MV F192525).

Type locality. Pacific Ocean, Bass Strait, off eastern Victoria, 38º19.10’E, 149º14.30’S, 600 m.

Diagnosis. Ovoid frontal lips; ceratophores without lateral projections; peristomial cirri present; first 2 pairs of parapodia with pseudocompound, bidentate falcigers with very long pointed hoods, shafts and appendages with scattered spines; subacicular hooks equal, starting from chaetiger 9; branchiae absent; delicate protomandibles.

Description. All examined specimens lacking posterior ends. Length of holotype 10.5 mm for 38 chaetigers, width 0.8 mm (at chaetiger 10, excluding parapodia); paratypes ranging from 4–20 mm long (20–80 chaetigers), 0.3–1.0 mm wide. Non-type material ranging from 0.2–0.8 mm in width. Alcohol stored specimens overall creamcoloured. Colour pattern of light brown dorsal segmental bands on chaetigers 2–37 visible in holotype and few other specimens, bleached or absent in most.

Prostomium anteriorly rounded, wider than long with paired ovoid frontal lips, separated by small gap ( Fig. 5 A–C). Palps of holotype reaching chaetiger 1 (paratypes: peristomium–chaetiger 1); lateral antennae reaching chaetiger 5 (chaetigers 3–5); median antenna reaching chaetiger 2 (chaetigers 1–2), style slenderer than those of lateral antennae ( Fig. 5 A, C). Ceratophores with well developed annulation, lacking lateral projections; ceratophores of lateral antennae with 4 (3–4) rings, median antenna with 3 (2–4) rings; terminal ring as long as three lower ones combined. Nuchal grooves short and slanted, with wide middorsal separation. Small eyespot at base of lateral antennae, present in holotype and 60% of paratypes, bleached or absent in remaining specimens. Peristomium as long as first chaetiger. Peristomial cirri present, short and tapering, about half as long as peristomium.

First two pairs of parapodia modified, projecting anterolaterally ( Fig. 5 A, B). Prechaetal lobes rounded on all parapodia; postchaetal lobes triangular to subulate in first chaetigers, decreasing rapidly in size, absent from chaetiger 8–9. Dorsal cirri well developed and subulate in anterior parapodia, becoming smaller and digitate in median region. Ventral cirri subulate on first three chaetigers, third one shorter than first two, replaced by rounded ventral lateral pads from chaetiger 4, changing to transverse ridges some chaetigers thereafter ( Fig. 5 B).

Parapodia supported by two aciculae projecting less than about half as far as falcigers and limbate chaetae from prechaetal lobes ( Fig. 6 A, C). First two pairs of parapodia with dorsal fascicle of 1–2 dorsal simple limbate chaetae and 4–5 bidentate pseudocompound falcigers with delicate subterminal tooth and very long pointed hoods ( Figs 5 D, 6B), hoods ranging from half to twice as long as appendage of falciger; shafts and appendages of falcigers with scattered small spines ( Fig. 5 D). Two fascicles of simple limbate chaetae starting from chaetiger 3 ( Fig. 6 C). Ventral fascicle of limbate chaetae replaced by paired, bidentate subacicular hooks ( Fig. 6 D) from chaetiger 9, hooks about equal in length and thickness. Pectinate chaetae slightly oblique with 14–18 teeth ( Fig. 5 E). Branchiae absent. Posterior end and tubes unknown.

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

Remarks. Most Paradiopatra species have three pairs of parapodia with falcigers. Besides P. longicappa , only five other species with two or two to three pairs of parapodia with falcigers are known and are here considered for their similarity to the new species. Paradiopatra capbretonensis Aguirrezabalaga et al., 2002 differs greatly in having ceratophores with lateral projections, and P. pauli ( Annenkova, 1952) in having branchiae. Paradiopatra longicappa shares with the remaining three species ( P. unica Imajima, 1999 ; P. fiordica ( Fauchald, 1974) ; P. spinosa n. sp.) the absence of branchiae, but differs in having bidentate rather than uni- to bidentate or tridentate falcigers and subacicular hooks from chaetiger 9 rather than after chaetiger 11. Paradiopatra longicappa n. sp. can further be distinguished from P. u n i c a and P. f i o rd i c a by having short antennae with the median antenna being very short and thinner than the laterals, and from P. s p i n o s a n. sp., by the very long hoods of its falcigers.

Etymology. The specific name longicappa refers to the very long hoods of the falcigers.

Distribution. Paradiopatra longicappa n. sp., was collected in two transects: off eastern Victoria in Bass Strait, and off Freycinet Peninsula, eastern Tasmania, in 400– 720 m.

Figures

FIGURE 5. SEM images of Paradiopatra longicappa n. sp. (AM W 43546.001). Anterior end, dorsal view; B, same, ventral view; C, enlarged anterior end, lateral view; D, distal part of parapodium 1 showing pseudocompound falcigers; E, pectinate chaetae from chaetiger 18.

FIGURE 6. Line drawings of Paradiopatra longicappa n. sp. (AM W 43546). A, Parapodium 1, anterior view; B, pseudocompound falciger from chaetiger 1; C, parapodium 3, anterior view; D, subacicular hook from chaetiger 20; E, mandibles; F, maxillae.