Syllis noolinga, Martín & Lucas & Hutchings, 2023

Martín, Guillermo San, Lucas, Yolanda & Hutchings, Pat, 2023, The genus Syllis Savigny in Lamarck, 1881 (Annelida: Syllidae: Syllinae) from Australia (Part 3): new species and redescription of previously described species, Zootaxa 5230 (3), pp. 251-295 : 270-273

Syllis noolinga n. sp.

Figures 10 , 11

Material examined. AUSTRALIA, NEW SOUTH WALES: Newport 33° 39’S, 151° 19’ E, coll. 22 July 2005, Corallina sp. in rock pools, AM W.53780, Holotype . Port Jackson, Fairlight , 33° 48’ S, 151° 17’E, coll. 19 Feb 2006, 0.5 m, subtidal brown algae, AM W.53781, Paratypes 2 specimens .

Diagnosis. Body slender. Two dark, almost black, transversal bands on each segment; most anterior segments with only one band. Dorsal cirri long, alternating in length in midbody segments. Compound chaetae with short, strongly bidentate blades. Posterior aciculae thick, slightly oblique distally. Pharynx and proventricle long.

Description. Holotype incomplete, only lacking most posterior segments and pygidium, with a stolon developing two heads ( Fig. 10C ), 9.2 mm long, 0.4 mm wide, 69 chaetigers (stolons included). Body elongated, with a distinctive colour pattern; anterior segments each with a single wide dark grey to black band of pigment, becoming a double band after 5–6 segments ( Fig. 10A ); after segments of proventricle, posterior band disappears, remaining as a single, anterior band on mid-posterior segments, and finally absent on most posterior segments. Prostomium semicircular, with two pairs of eyes in open trapezoidal arrangement, and two anterior eyespots ( Fig. 10A ). Palps robust, similar in length to prostomium. Median antenna inserted between eyes, longer than combined length of prostomium and palps together, with 16–18 articles; lateral antennae much shorter, with about 15 articles, inserted in front of anterior eyes. Peristomium shorter than subsequent segments, forming a small lobe dorsally ( Fig. 10A ). Dorsal tentacular cirri similar in length to lateral antennae, with 15 articles; ventral tentacular cirri shorter than dorsal ones, with 10 articles; both dorsal and ventral tentacular cirri difficult to see, covered by dorsal cirri of anterior segments. Dorsal cirri of anterior segments distinctly long and thick, with about 25–20 to 23–25 articles on most anterior segments; subsequent segments also with long dorsal cirri, longer than body width, alternating long and short, long ones with 23–25 articles, short ones with 15–18 articles ( Fig. 10A, B ). Parapodial lobes subrectangular, slightly bilobed distally; ventral cirri digitiform, shorter than parapodial lobes. Compound chaetae distinctly bidentate falcigers, relatively short, with proximal tooth acute, shorter than distal one, and short, slightly distally curved, spines on margin ( Fig. 11A–C ). Anterior parapodia each with 10–12 chaetae, blades with dorso-ventral gradation, 35 µm above, 25 µm below ( Fig. 11A ); midbody parapodia with eight chaetae, thicker than those of anterior segments, and less marked dorso-ventral gradation in length, 27 µm above, 22 µm below ( Fig. 11B ); posterior parapodia each with six chaetae, with thick shafts and relatively short, large blades, all similar, 25–22 µm long ( Fig. 11C ). Anterior parapodia each with three slender aciculae, one acute, one distally blunt and one forming almost a right angle ( Fig. 11D ); midbody parapodia with two aciculae each, one slender, distally slightly oblique and one much thicker, almost straight, distally slightly oblique ( Fig. 11E ), slightly protruding from parapodial lobes; posterior parapodia with single, thick acicula, almost straight, slightly oblique distally ( Fig. 11F ). Dorsal simple chaetae on posterior parapodia, unidentate, distally blunt, smooth ( Fig. 11G ). Ventral simple chaetae on most posterior parapodia, very slender, smooth, distally slightly bidentate ( Fig. 11H ). Pharynx long, through about 14 segments; pharyngeal tooth located on anterior margin ( Fig. 10A ). Proventricle long, through about 7–8 segments; number of muscle cell rows difficult to assess, since the pigmentation covers part of them; about 40.

Holotype is developing an unusual stolon, apparently with two heads separated by two segments ( Fig. 10C ), packed with oocytes; each head is provided with one pair of large dorsal and one pair of ventral eyes, but only the anterior head shows a pair of short, non-articulate ventral appendages ( Fig. 10C ).

Remarks. Syllis noolinga n. sp. is characterized by its distinctive colour pattern, with a single-double-single band of dark, almost black, pigmentation per segment on anterior segments, strongly bidentate blades and thick posterior acicula, with tips extending slightly from the parapodial lobes. No other species of this genus has this combination of characters. The compound chaetae and aciculae are similar to those of Syllis corallicola Verrill, 1900 from the Caribbean region and the Mediterranean, and especially to those of Syllis columbretensis Campoy, 1982 from the Mediterranean, but the colour pattern and simple dorsal and ventral chaetae are different, and the blades of compound chaetae of Syllis noolinga n. sp. have longer spines on margin (see Licher 1999; San Martín 2003). The most similar species is Syllis schulzi ( Hartmann-Schröder, 1960) from the Red Sea and Southern Mediterranean (San Martin 2003, Ba-Akdah et al. 2018); aciculae and chaetae are very similar, but the pigmentation pattern is different, being reddish, with one anterior large band and another narrow one in the posterior segments in S. schulzi ; furthermore, the proventricle is much shorter in S. schulzi , through four segments, being much longer in S. noolinga n. sp. ( Hartmann-Schröder 1960; San Martín 2003; Ba-Akdah et al. 2018). Finally, Syllis marugani Aguado, San Martín & Nishi, 2006 , from Japan, has similar compound chaetae and also thick anterior dorsal cirri, but the aciculae are slender, and the colour pattern is different, being orange-red in S. marugani ( Aguado et al. 2006) .

The holotype of Syllis noolinga n. sp. is developing an unusual stolon, with two heads; only one other has been described with this type of stolon, S. ergeni Çinar, 2005 , from Turkey, but that species is very different, having a bright orange colour and other kinds of chaetae and aciculae (see Çinar 2005).

Etymology. The name noolinga comes from the aboriginal word meaning “dark”, in reference to its distinctive pigmentation pattern.

Habitat. Among algae, intertidal and subtidal.

Distribution. Australia (NSW).

Figures

FIGURE 10. Syllis noolinga, n. sp. Holotype, AM W.53780. A, anterior end, dorsal view. B, midbody long and short dorsal cirri. C, heads of the stolon. Scales. A, B: 0.1 mm. C: 0.2 mm.

FIGURE 11. Syllis noolinga, n. sp. Holotype, AM W.53780. A, falcigers, anterior parapodium. B, falcigers, midbody parapodium. C, falcigers, posterior parapodium. D, aciculae, anterior parapodium. E, aciculae, midbody parapodium, F, acicula, posterior parapodium. G, dorsal simple chaeta. H, ventral simple chaeta. Scale. 20 µm.