Astreptosyllis similiseta Hartmann-Schröder, 1986

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 : 269

Astreptosyllis similiseta Hartmann-Schröder, 1986

Fig. 9A–H

Astreptosyllis similiseta Hartmann-Schröder, 1986: 40 , figs 16–21.

Material examined. AUSTRALIA: SOUTH AUSTRALIA: Port Augusta , 32°30'S 137°13'E, intertidal sediments, 6 Dec 1975, holotype ( HZM P-18624) and 3 paratypes ( HZM P- 18625), coll. G. Hartmann-Schröder.

Description. Body, delicate, fragile, entire, without colour markings, 1.8–2.0 mm long, 0.1 mm wide, with 23–28 chaetigers. Prostomium semi-circular, with 4 eyes in open trapezoidal arrangement; antennae fusiform to club-shaped, smooth; median antenna longer than combined length of prostomium and palps, inserted on middle of pharynx, between anterior eyes; lateral antennae similar in shape to median antenna, but shorter, inserted near anterior margin of prostomium ( Fig. 9A). Palps small, shorter than prostomium, fused basally ( Fig. 9A). Peristomium similar in size to subsequent segments; tentacular cirri smooth, slightly club-shaped ( Fig. 9A); dorsal tentacular cirri similar in length to lateral antenna, ventral ones shorter than dorsal ones. Dorsal cirri of anterior 2 chaetigers similar in shape to antennae and tentacular cirri, and slightly longer; dorsal cirri from chaetiger 3 onwards articulated, with some dark granular inclusions on some articles ( Fig. 9A,B), 5–7 articles on midbody chaetigers. Parapodia slender, elongated; ventral cirri digitiform, longer on posterior parapodia ( Fig. 9B) becoming of similar length to parapodial lobes. Compound chaetae heterogomph falcigers, with conspicuous spines subdistally on shafts, and unidentate blades with short, apparently smooth spines on margin. Anterior parapodia (1–5 chaetigers) each with several compound chaetae, with slight dorsoventral gradation in length of blades within fascicle, 40 µm in length dorsally, 20 µm in length ventrally ( Fig. 9D); on midbody blades of compound chaetae longer, more marked gradation (65 µm dorsally and 23 µm ventrally) ( Fig. 9F); posterior parapodia with less marked dorsoventral gradation in length of blades within fascicle (40 µm dorsally and 23 µm ventrally) ( Fig. 9G). Dorsal simple chaetae thick, distally unidentate, with distinct distal hood longitudinally striated, similar throughout ( Fig. 9C,E,H), present from anterior parapodia. Ventral simple chaetae absent. Pharynx through about 5 segments; proventricle through 4.5 segments ( Fig. 9A), with 38–40 muscle cell rows. Pygidium rounded, with single digitiform