Paraopisthosyllis ornaticirra, San Martin & Hutchings, 2006

San Martin, G & Hutchings, PA, 2006, Eusyllinae (Polychaeta: Syllidae) from Australia with the Description of a New Genus and Fifteen New Species, Records of the Australian Museum 58, pp. 257-370 : 320-321

Paraopisthosyllis ornaticirra n.sp.

Fig. 54A–K

Material examined. HOLOTYPE ( AM W28949) AUSTRALIA: WESTERN AUSTRALIA: Inshore limestone reef, Ned’s Camp, Cape Range National Park , 21°59'S 113°55'E, Caulerpa sp. , 1 m, coll. J.K. Lowry, 2 Jan 1984.

Description. Complete specimen. Body broad and robust anteriorly, tapered posteriorly, 7.8 mm long, 0.6 mm wide, with 63 chaetigers. Segmented pigmentation absent, but median antenna and anterior dorsal cirri each with 2 dark transverse areas, large dorsal cirri with more extensive pigmented area, anal cirri with single transverse band of pigment ( Fig. 54A,C,D). Dorsal and ventral surfaces densely covered with small, rounded papillae ( Fig. 54A). Prostomium rectangular, with 2 pairs of eyes arranged almost in line. Lateral antennae inserted in front of eyes, relatively short and slender; median antenna longer and thicker than lateral antennae, arising between eyes ( Fig. 54A). Palps broad, as wide as prostomium, ventrally folded ( Fig. 54A,B). Peristomium dorsally reduced, covered by chaetiger 1; dorsal tentacular cirri similar in shape to median antenna slightly longer and thicker, ventral tentacular cirri similar but smaller than dorsal ones. Dorsal cirri of chaetigers 1, 4, and 6 distinctly longer and larger than remaining dorsal cirri, inflated, except for chaetiger 6, with digitiform, non-pigmented terminal lobe, arising dorsolaterally ( Fig. 54A). Remaining dorsal cirri with cirrophores; cirrostyles tapered, fusiform, shorter than half of body width, with 1–2 bands of dark pigment, midbody dorsal cirri lacking such pigment ( Fig. 54D); posterior dorsal cirri oval, shorter than those of anterior chaetigers. Parapodia with anterior and posterior lobes ( Fig. 54D). Compound chaetae with thick shafts, distally provided with strong serration, and short, strongly bidentate blades, with short, few spines on margin; anterior parapodia with about 15 compound chaetae, blades slender ( Fig. 54F), about 13 µm in length. Compound chaetae becoming progressively thicker posteriorly, with blades bidentate; about 10–14 compound chaetae on midbody parapodia, blades 10–12 µm in length, terminal teeth increasing in size ventrally within fascicle ( Fig. 54G). Number of compound chaetae per parapodium decreasing posteriorly, with only 3 on most posterior parapodia, similar to those of midbody ( Fig. 54I). Dorsal simple chaetae on posterior parapodia, distally serrated and bifid ( Fig. 54J). Ventral simple chaetae on most posterior parapodia, thick, strongly bidentate, smooth on margin ( Fig. 54K). Anterior parapodia with 3 aciculae, distally rounded ( Fig. 54E), posteriorly single acicula present, slightly bent at tip ( Fig. 54H). Pharynx wide, through 3–4 segments; pharyngeal tooth located posteriorly. Proventricle similar in size to pharynx, with 30–35 muscle cell rows. Pygidium trapezoidal; anal cirri larger than posterior dorsal cirri, oval to egg-shaped.

Remarks. This species is easily distinguished from the other members of this genus by the shape of the enlarged dorsal cirri of chaetigers 1, 4, and 6, the pigment pattern present on the dorsal cirri and median antenna, and the presence of compound chaetae with strongly bidentate blades.