Sphaerosyllis voluntariorum, Guillermo San Martin, 2005

Sphaerosyllis voluntariorum View in CoL n.sp.

Fig. 44A–I View Fig

Material examined. AUSTRALIA: WESTERN AUSTRALIA. HOLOTYPE: AM W26821, Ningaloo reef off Ned’s Camp, Cape Range National Park, 21°59.5'S 113°54.5'E, mixed algae, 2 m, J.K. Lowry, 1 Jan 1984.

Description. Body small, slender, 1.4 mm long, 0.14 mm wide, 26 chaetigers. Papillae numerous ( Figs. 44A,B,C View Fig ) covering dorsum, few papillae on parapodia; papillae long, distinct, with slender stalk and expanded, rounded or slightly trilobed tips, with dark inclusions. Papillae absent on prostomium and palps. Prostomium ovate to trapezoidal, wider than long; 4 large eyes in trapezoidal arrangement. Antennae relatively long, with bulbous bases and long, slender tips, similar to combined length of prostomium and palps ( Fig. 44A View Fig ). Palps similar in length to prostomium, fused along their length, ventrally folded. Peristomium similar in length to following segments, covering posterior half of prostomium; tentacular cirri shorter than antennae. Dorsal cirri similar to tentacular cirri, similar in length to parapodial lobes, with bulbous bases and slender tips ( Fig. 44A,C View Fig ), elongate on midbody. Parapodial lobes conical, provided with 2 subdistal, rounded papillae ( Fig. 44A,C View Fig ), and sometimes few other basal papillae similar to dorsal papillae ( Fig. 44C View Fig ). Ventral cirri relatively long, slender. Parapodial glands small, difficult to see, with granular material ( Fig. 44A,C View Fig ). Anterior parapodia each with 5 compound chaetae with unidentate blades ( Fig. 44D View Fig ); blades of dorsal compound chaetae with moderate, straight marginal spines, about 12 µm long, blades of ventral compound chaetae smooth, about 9 µm long. Number of compound chaetae on each parapodium diminishing posteriorly to 3 on posterior parapodia, with thick shafts provided with strong subdistal spur giving bifurcate appearance, and hooked blades, smooth, provided with a long, distinct subdistal spine on most dorsal compound chaetae ( Fig. 44G View Fig ), about 10–9 µm long. Dorsal simple chaetae from chaetiger 1, unidentate, with few subdistal marginal spines ( Fig. 44F View Fig ). Ventral simple chaetae on posterior parapodia, sigmoid, distally hooked, unidentate, smooth, provided with a long, distinct subdistal spine ( Fig. 44H View Fig ). Parapodia each with solitary, slender acicula, bent to a right angle ( Fig. 44E,I View Fig ). Pygidium small, with numerous, rounded papillae, and 2 anal cirri, similar to dorsal cirri but much longer ( Fig. 44B View Fig ). Pharynx through 3 segments; pharyngeal tooth not seen; probably located on anterior rim ( Fig. 44A View Fig ). Proventricle through 1–2 segments, with 12 muscle cell rows.

Remarks. This species is closely related to Sphaerosyllis bifurcata , S. bifurcatoides and S. rotundipapillata , all Australian endemic species, all characterized by having large, distinct dorsal papillae, distally rounded or trilobed, and shafts of compound chaetae distally bifid. Sphaerosyllis voluntariorum is represented by a single specimen, but it is distinctly different to these three species because it is more densely papillated on anterior segments and by having a long, distinct subdistal spine on the ventral simple chaetae and on the blades of dorsalmost, posterior compound chaetae.

Distribution. Australia (Western Australia).

Habitat. On algae, 2 m depth.

Etymology. This species is dedicated to the volunteers of the Marine Invertebrate section of The Australian Museum, who sorted samples from all around Australia, extracting specimens of syllids for this study.