Parapionosyllis richardi

Guillermo San Martin, 2005, Exogoninae (Polychaeta: Syllidae) from Australia With the Description of a New Genus and Twenty-two New Species, Records of the Australian Museum 57, pp. 39-152 : 107-108

Parapionosyllis richardi n.sp.

Fig. 61A–G

Material examined. AUSTRALIA: WESTERN AUSTRALIA. HOLOTYPE: AM W27398, north end of beach, Bundegi Reef, Exmouth Gulf, 21°49'S 114°11'E, rocky rubble, coralline algae with green epiphyte, 2 m, H.E. Stoddart, 4 Jan 1984. PARATYPES: 2 specimens, AM W26799, north east entrance to Goss Passage, Beacon Island, 28°27.9'S 113°46.7'E, dead plates of Acropora , covered in coralline algae, 8 m, P.A. Hutchings, 25 May 1994.

Description. Body minute, holotype 1.12 mm long, 0.13 mm wide, for 20 chaetigers, paratype in two pieces, 2.5 mm long, 0.1 mm wide, for 27 chaetigers. Prostomium ovate, wider than long, with 4 small eyes in trapezoidal arrangement and 2 anterior small eyespots, anterior eyes larger than posterior eyes, reniform.Antennae thick, spindleto bowling-pin shaped, with distinct median enlargement; median antenna longer than lateral ones, shorter than prostomium and palps together, inserted between posterior eyes; lateral antennae similar in length to prostomium, inserted in front of anterior eyes and just lateral to eyespots, similar in shape to median antenna. Palps similar in length to prostomium, fused for their basal half (Fig. 61A). Peristomium shorter than following segments; tentacular cirri similar to lateral antennae but shorter. Parapodial glands small, with dark, granular material, usually 2 glands per parapodium. Dorsal cirri bowling-pin shaped (Fig. 61A), longer than parapodial lobes. Parapodial lobes conical, with a small, thin distal rounded papilla. Ventral cirri digitiform, shorter than parapodial lobes. Compound chaetae similar throughout, (Fig. 61D,G); blades unidentate, distally distinctly rounded, slightly hooked, marginal spines moderate in length; subdistal spine near tip, similar to other spines but slightly longer and thicker (Fig. 61D,G). Parapodia each with about 6–8 compound chaetae, blades 18 µm above 6 µm below in midbody segments (Fig. 61G); chaetae of anterior parapodia with slightly shorter blades (Fig. 61D), diminishing progressively in length, 10 µm above, 5 µm below; long blades disappearing in posteriormost parapodia. Dorsal simple chaetae from chaetiger 1, unidentate, provided with about 4–5 short spines of similar size (Fig. 61F), anterior dorsal simple chaetae slender (Fig. 61C). Ventral simple chaetae on most posterior parapodia, sigmoid, with short marginal spines and unidentate (Fig. 61E). Solitary acicula in each parapodium, tip enlarged and rounded, slightly hollow. Pharynx similar in length to proventricle, through 2 segments; pharyngeal tooth conical, located on anterior margin (Fig. 61A). Proventricle short, through 2–2½ segments, with about 13 muscle cell rows. Pygidium small, bilobed, with two anal cirri, similar to posterior dorsal cirri, but longer (Fig. 61B).

Remarks. Parapionosyllis richardi n.sp., is characterized by having compound chaetae with a strong gradation in length of blades, provided with moderately long marginal spines and dorsal simple chaetae with few teeth, all similar in size. Parapionosyllis macaronesiaensis Brito, Núñez & San Martín (2000), from Canary and Madeira Islands (see Brito et al., 2000), has similar chaetae, but the dorsalmost compound chaetae are provided with long blades and the remaining are much shorter, with a dorsoventral gradation, and the dorsal simple chaetae have 2 teeth longer than the rest. The most similar species appears to be Parapionosyllis elegans (Pierantoni, 1903) ; both species have compound chaetae with moderately long marginal spines and gradation in size of blades. The antennae of P. elegans , however, have a smaller enlargement, longer the proventricle, the ventral simple chaetae are smooth, and the dorsal simple chaetae have a distinctly longer and thicker tooth (see Pierantoni, 1903; San Martín, 2003). Parapionosyllis uebelackerae San Martín (1991b), from the Gulf of México, is a larger species, with longer blades on the compound chaetae, although the dorsal simple chaetae are similar (San Martín, 1991b).

Distribution. Australia (Western Australia).

Habitat. In dead corals.

Etymology. The species is dedicated to Mr Richard Johnson, of The Australian Museum.