Pionosyllis heterochaetosa, 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 : 331-334

Pionosyllis heterochaetosa n.sp.

Figs 62D–F, 63A–O, 64A–F

Material examined. HOLOTYPE ( AM W21629) AUSTRALIA: NEW SOUTH WALES: S of airport runway extension, Botany Bay , 33°58.13'S 151°11.16'E, muddy sand, 5 m, coll. Australian Museum party, 6 Apr 1992 . PARATYPES S of airport runway extension, Botany Bay , 33°58.13'S 151°11.16'E, muddy sand, 5 m, Australian Museum party, 27 July 1992, 3 on SEM stub ( AM W22117) ; S of airport runway extension, Botany Bay , 33°58.10' 151°11.16'E, muddy sand, 5 m, coll. Australian Museum party, 27 July 1992, 2 ( AM W22110) ; S of airport runway extension, Botany Bay , 33°58.13'S 151°11.16'E, muddy sand, 5 m, Australian Museum party, 6 Apr 1992, 2 ( AM W22112) ; S of airport runway extension, Botany Bay , 33°58.13'S 151°11.16'E, muddy sand, 5 m, coll. Australian Museum party, 27 July 1992, 1 on SEM stub ( AM W22116) . S of airport runway extension, Botany Bay , 33°58.13'S 151°11.16'E, muddy sand, 5 m, coll. Australian Museum party, 27 July 1992, 2 ( AM W22115) .

Description. Body 4.6 mm long, 0.2 mm wide, with 54 chaetigers. Prostomium circular, with 4 eyes in open trapezoidal arrangement (Fig. 63A); median antenna long, about 3 times longer than combined length of prostomium and palps, inserted between posterior eyes; lateral antennae

Fig. 62. SEM of Pionosyllis koolalya n.sp. (A) compound chaeta, midbody; (B) dorsal simple chaeta; (C) ventral simple chaeta and falciger, posterior parapodium. SEM of Pionosyllis heterochaetosa n.sp. (D) anterior end, dorsal view; (E) compound chaetae, anterior parapodium; (F) fascicles of chaetae, midbody. A–C: paratype, AM W28409; D–F: paratype, AM W22117.

about half or third length of median antenna, inserted near anterior margin. Palps broad, longer than prostomium (Figs 62D, 63A). Peristomium shorter than subsequent segments; dorsal tentacular cirri elongated, filiform, similar to median antenna, ventral tentacular cirri smaller. Dorsum of anterior segments each with transverse band of cilia (Figs 62D, 63A); double row from proventricle segments onwards. Dorsal cirri elongated, slender, smooth, filiform, varying in length in different specimens and in each specimen, some cirri long, several times longer than body width, and some cirri shorter than body width, alternating irregularly (Figs 62D, 63A). Anterior parapodia broad, becoming conical and slender from proventricle segments posteriorly. Ventral cirri digitiform, shorter than parapodial lobes anteriorly, elongated on posterior parapodia, longer than parapodial lobes. Most anterior parapodia with numerous compound chaetae, about 10–15, slightly enlarged shafts, and short, bidentate blades, provided with long spines on margin (Figs 62D,E, 63B), especially on more dorsal chaetae, extending beyond distal tooth, and dorsoventral gradation in length within fascicle, about 16 µm in length dorsally, 5–6 µm in length ventrally. Progressively along body, number of compound chaetae per parapodium decreasing, and blades of more dorsal compound chaetae becoming elongate and more strongly bidentate (Fig. 63C); on chaetiger 5, blades about 22 µm in length dorsally, 12 µm in length ventrally. From proventricular segments, parapodia with 2–3, sometimes only 1, compound chaetae with elongate,

Fig. 63. Pionosyllis heterochaetosa n.sp. (A) anterior end, dorsal view; (B) compound chaetae, anteriormost parapodium; (C) compound chaetae, anterior parapodium; (D) spiniger-like compound chaeta, mid-anterior parapodium; (E) compound chaetae, mid-anterior parapodium; (F) spinigerlike compound chaeta, midbody; (G) compound chaetae, midbody; (H) spiniger-like compound chaeta, posterior parapodium; (I) compound chaetae, posterior parapodium; (J) dorsal simple chaeta, anterior parapodium; (K) same, midbody; (L) same, posterior parapodium; (M) ventral simple chaeta; (N) aciculae, anterior parapodium; (O) acicula, posterior parapodium. AM W21629 (holotype). Scales: A 0.18 mm, B–O 20 µm.

spiniger-like blades (Fig. 62F), about 112 µm in length, weakly bidentate distally, with moderate spines on margin (Fig. 63D,F,H), and 5–6 compound chaetae with falcigerous, bidentate blades, slender, margin with long, distinct, distally pointed basal spines and thin, fine, spines distally (Figs 62F, 63E,G,I, 64B–D), reaching level of distal tooth, and dorsoventral gradation in length within fascicle, 25 µm dorsally, 15 µm ventrally. Dorsal simple chaetae from proventricle segments, distally broad, provided with short spines on margin (Figs 63J–L, 64E). Ventral simple chaetae on posterior segments, bidentate, proximal tooth prominent, slightly longer than distal tooth, and some thin spines on margin, 2–3 distal ones longer than others, reaching to level of distal tooth (Figs 63M, 64F). Aciculae distally knobbed, with 2 lateral, unequal lobes (Fig. 63 O); 2 aciculae on anterior parapodia (Fig. 63N). Pharynx slender, through about 6–7 segments (Fig. 63A). Proventricle through 6 segments, with about 24 muscle cell rows. Pygidium small, with 2 filiform anal cirri.

Remarks. Pionosyllis heterochaetosa n.sp. is characterized by having anterior parapodia without spiniger-like compound chaetae, which appear in post- proventricle segments. Pionosyllis serrata and P. koolalya , described above, also lack spiniger-like chaetae anteriorly, and posteriorly. All other species of the genus ( P. hartmannschroederae and P. augeneri described below, as well as P. spinisetosa San Martín, 1990 , from Cuba, and P. anophthalma Capaccioni & San Martín, 1989 , from the western Mediterranean Sea), have spiniger-like compound chaetae from chaetiger 1 (see San Martín, 1990, 2003), as well as P. longisetosa ( Hartmann-Schröder, 1965) from Chile (see Hartmann-Schröder, 1965).

Distribution. Australia (New South Wales).

Habitat. Occurring in muddy sand at about 5 m depth.

Etymology. The specific name refers to the presence of different chaetae on anterior segments compared to others.