Syllis joaoi, Martín, Guillermo San, Álvarez-Campos, Patricia & Hutchings, Pat, 2017

Martín, Guillermo San, Álvarez-Campos, Patricia & Hutchings, Pat, 2017, The genus Syllis Savigny in Lamarck, 1818 (Annelida: Syllidae: Syllinae) from Australia (second part): four new species and re-description of twelve previously described species, Zootaxa 4237 (2), pp. 201-243 : 210-212

Syllis joaoi n. sp.

Figure 5

Material examined. AUSTRALIA, NORTHERN TERRITORY: Darwin Harbour, off Nightcliff , Old Man's Rock , 12° 28' 30" S, 130° 54' 12" E, holotype, AM W.48533, coll. 17 July 1993.

Description. Holotype incomplete, lacking most posterior segments, 7 mm long, 0.45 mm wide, with 55 chaetigers. Body slender, elongated, darker on anterior segments, with reddish spots, extending also to prostomium. Prostomium pentagonal; 4 eyes in open trapezoidal arrangement. Palps similar in length to prostomium ( Fig. 5 A). Antennae, tentacular and dorsal cirri distinctly short and slender. Median antenna arising from middle of prostomium, with about 13 articles, shorter than combined length of prostomium and palps; lateral antennae similar to median one, with 12–14 articles. Segmental furrows indistinct ( Fig. 5 A). Peristomium dorsally reduced. Dorsal tentacular cirri longer than median antenna, with about 20 articles; ventral tentacular cirri much shorter, with 10 articles. Dorsal parapodial cirri distinctly short and slender, shorter than body width ( Fig. 5 A), anteriormost parapodial cirri slightly shorter than dorsal tentacular cirri, with about 15–12 articles; midbody long dorsal parapodial cirri with 12–13 articles and short parapodial dorsal cirri with 8–9 articles. Parapodia conical. Ventral parapodial cirri shorter than parapodial lobes. Compound chaetae with elongated bidentate blades, proximal tooth shorter than distal tooth; dorsal chaetae with long and slender blades with short spines on margin, except on the distal regions, where they are longer, reaching the level of the proximal tooth; intermediate chaetae of each fascicle with shorter blades with long, distally curved spines; ventral chaetae with short blades, provided with short spines on margin ( Fig. 5 B–D). Anterior parapodia each with 1–2 compound chaetae of the first type, 3–4 of the second one, and 2–3 of the third type, with blades 36 µm long above, 15 µm long below ( Fig. 5 B); midbody parapodia with 1 compound chaetae of the first type, 3 of second type, and 2 of the third type, with blades 35 µm long above, 15 µm long below ( Fig. 5 C); posterior parapodia with 1 compound chaetae of the first type, 2 of the second one, and 1 of the third type, with blades 34 µm above, 15 µm below ( Fig. 5 D). Dorsal and ventral simple chaeta not seen. Aciculae slender, anterior parapodia with 3 aciculae, 2 acute and 1 distally curved ( Fig. 5 E), 2 aciculae in midbody parapodia, 1 straight and 1 acuminate ( Fig. 5 F), and solitary acicula in posterior parapodia, subdistally inflated, acuminate ( Fig. 5 G). Pharynx extending through about 11 segments; pharyngeal tooth on anterior margin of pharynx ( Fig. 5 A). Proventricle through 10–11 segments, with about 55 muscle cell rows. Pygidium unknown.

Remarks. Although having one single and incomplete specimen available, it is here describe as a new species as it is the only known species in the genus to present such slender and short dorsal cirri, together with the described distribution of the compound chaetae, with elongated blades with short spines in margin dorsally combined with blades with long, distally dressed spines on the middle of the fascicle, and short blades with short spines in the chaetae of the ventral bundle.

The most similar species is Syllis aciculigrossa ( San Martín, 1990) , with elongated, slender body and short, delicate dorsal cirri; however, S. aciculigrossa has distinctly thick aciculae, distally pointed, protruding from parapodial lobes, and elongated spiniger-like chaetae ( San Martín, 1990). Syllis nigricirris Grube, 1863 has similar compound chaetae, but lacks the long spines on margin, and the aciculae are straight, protruding from parapodial lobes (see Licher, 1999).

Etymology. The new species is named after Dr João Miguel do Matos Nogueira, colleague and friend, for his contributions to the knowledge of some families of polychaetes, including the Syllidae .

Habitat. Dead coral substrate in shallow waters.

Distribution. Australia (Northern Territory).

Figures

FIGURE 5. Syllis joaoi, n. sp. (AM W. 48533). A, anterior end, dorsal view. B, compound chaetae, anterior parapodium. C, compound chaetae, midbody parapodium. D, compound chaetae, posterior parapodium. E, aciculae, anterior parapodium. F, aciculae, midbody parapodium. G, acicula, posterior parapodium. Scale bars: A: 0.4 mm. B – G: 20 µm.