Odontosyllis robustus, Aguado, M. Teresa, Murray, Anna & Hutchings, Pat, 2015

Aguado, M. Teresa, Murray, Anna & Hutchings, Pat, 2015, Syllidae (Annelida: Phyllodocida) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 35-60 : 39-41

Odontosyllis robustus n. sp.

( Figs 1 B, D, F, 2A–C, 3A–E)

Material examined. Holotype, AM W.44768, MI QLD 2380. Paratype, AM W.44755, MI QLD 2387 (1 on 2 SEM pins).

Description. Holotype, AM W.44768 is 5 mm long, 1.3 mm wide, with 29 chaetigers, adult specimen. Body broad and robust, dorsally spherical, ventrally flattened ( Figs 1 B, D, F). Live specimens with distinct colour pattern consisting of segments with and without lateral reddish-brown pigmentation. Colouration especially conspicuous in segments 2–3, 7–8, 13, 19, 23; all segments with a pair of reddish-brown spots laterally on dorsum; and chaetigers 4–6 each with one red spot in the midline of dorsum ( Figs 1 B, 2A). Some segments with dorsal bumps ( Fig. 1 D). Parapodia with distal white colouration ( Figs 1 D, F). Ventral colour pattern consisting of irregular redbrown pigment ( Fig. 1 D). Integument full of glandular material. Some segments and parapodia with fibrillar material arising from the surface. Prostomium wider than long, anterolaterally expanded, with two pairs of red eyes in trapezoidal arrangement, one pair of anterior eye spots ( Fig. 2 A). Antennae short and digitiform, lateral ones inserted on anterior margin of prostomium; middle antenna slightly posterior. Large white occipital flap semicircular, covering half of prostomium. Palps broad, shorter in length than prostomium. Peristomium shorter than subsequent segments. Tentacular cirri digitiform, anteriorly directed, longer than parapodia. Dorsal cirri of first chaetiger anteriorly directed. Subsequent dorsal cirri fusiform, slightly shorter than dorsal tentacular cirri, alternating in orientation up and down, those pointing up arising more dorsally from segment. Ventral cirri wide, shorter than parapodial lobes, proximally inserted. Parapodia rectangular in shape, with one rounded postchaetal lobe. Chaetal fascicle with approximately 20 compound heterogomph falcigers in midbody parapodia. Compound chaetae with bidentate blades, distal tooth minute, shorter than proximal one, distal blade edge with spines, blades exhibiting dorsoventral gradation in length ( Figs 2 B, 3A–E). Blades ~ 16 µm in length dorsally, ~ 10 µm in length ventrally on midbody. Anterior, midbody and posterior blades similar in length. Parapodia with one acicula, distally curved ( Fig. 2 C). Pharynx short, through approximately 5 segments in holotype, with 5 teeth directed backwards and two lateral plates. Proventricle through ~ 5 segments. Pygidium with two short anal cirri.

Remarks. The animals are quite broad and robust, with dorsal bumps and a distinct colour pattern. The chaetae are different to any described species. The species with the most similar chaetae is O. freycinetensis , which has unidentate blades; however, blades of O. robustus n. sp. are bidentate in all chaetigers, also shorter and distally wider.

Habitat. Halimeda algae, in shallow waters.

Distribution. Australia (Queensland).

Etymology. The name comes from the Latin word “ robustus ” and refers to the robust body shape of this animal.

Figures

FIGURE 2. Odontosyllis robustus n. sp. AM W. 44768; A. Anterior end, dorsal view; B. Mid-body chaetigers, bidentate chaetae; C. Acicula, posterior chaetiger. Scale bars: A = 0.1 mm; B, C = 2 µm.

FIGURE 1. A. Amblyosyllis sp. AM W. 47194, dorsal view; B. Odontosyllis robustus n. sp. AM W. 44768, dorsal view; C. Odontosyllis sp. 1, AM W. 47187, dorsal view; D. Odontosyllis robustus n. sp., lateral view, arrows pointing parapodia with a distal white ring and dorsal bump; E. Odontosyllis sp. 1, ventrolateral view; F. Odontosyllis robustus n. sp., ventral view.