Syllis sp.

Martín, Guillermo San, Lucas, Yolanda & Hutchings, Pat, 2024, The genus Syllis Savigny in Lamarck, 1818 (Annelida: Syllidae: Syllinae) from Australia (Fourth part), Zootaxa 5453 (1), pp. 1-32 : 18-21

Syllis sp.

Figure 13

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberley region, Stn. 50, East Montalivet Island , 15° 6’ S, 125° 18’ E, coll. P. A Hutchings, intertidal, 16 Jul 1988, AM W.54220, 1 specimen .

Description. Incomplete specimen, 5.5 mm long, 1.5 mm wide, with 33 chaetigers; lacking posterior segments. Body relatively long, stout anteriorly, with some rounded, small dermal inclusions and two transverse dark reddish bands on dorsum ( Fig. 13A ). Prostomium wider than long, with two pairs of eyes in open trapezoidal arrangement and some small spots of pigment. Median antenna inserted near middle of prostomium, distinctly longer than combined length of prostomium and palps, with about 38 short articles; lateral antennae shorter than median one, inserted in front of anterior eyes, with about 17 articles ( Fig. 13A ). Palps similar in length to prostomium. Peristomium shorter than subsequent segments. Dorsal tentacular cirri longer than lateral antennae, with about 38 articles, ventral tentacular cirri about half as long as dorsal ones, with about 12 articles. First dorsal cirri longer than tentacular dorsal cirri and median antenna, with about 48 articles ( Fig. 13A ). Dorsal cirri, tentacular cirri and antennae all similar, long, very slender, whip-shaped, with short articles. Thereafter, cirri alternating in length, with about 18₋₋30 articles. Parapodia with prechaetal and postchaetal small lobes. Ventral cirri conical, inserted proximally on parapodia, not extending beyond parapodial lobes. Compound heterogomph chaetae numerous on each parapodium, all similar along body, about 18₋₋20 on each anterior parapodia, 16₋₋18 on midbody parapodia, all similar. Compound chaetae with blades bidentate, both teeth similar, acute, well separated from each other, with very short spines on cutting edge, decreasing slightly in length from dorsal (28 µm) to ventral (22 µm) ( Fig. 13B, C ). Dorsal and ventral simple chaetae not seen. Parapodia with two aciculae, one distally blunt and other slender, distally oblique ( Fig. 13 D, E ). Pharynx slender, extending through 6₋₋7 segments; pharyngeal tooth elongated, relatively long, dagger-shaped ( Fig. 13A ). Proventricle large, barrel-shaped extending through six segments, with about 26 muscle cell-rows ( Fig. 13A ).

Remarks. The single specimen shows some unusual characters which do not fit with any other described species of Syllis . However, it is similar to some species described or assigned to the genus Megasyllis San Martín, Hutchings & Aguado, 2008b . Megasyllis eduardoi San Martín, Aguado & Álvarez-Campos, 2014 , from New Zealand, has similar chaetae, but with a shorter pharynx, the prostomium is almost covered dorsally by the peristomium, and is provided with numerous dermal inclusions, without any colour pattern. Megasyllis glandulosa ( Augener, 1913) from Western Australia has a small pharynx with a minute pharyngeal tooth. Probably, the most similar species is Megasyllis subantennata ( Hartmann-Schröder, 1984) , from South and Western Australia, but the shafts of compound chaetae are markedly denticulated on the margin, and the pharyngeal tooth is not as long as in Syllis sp. Finally, Megasyllis tigrina San Martín, Aguado & Álvarez-Campos, 2014 , from New South Wales, has a very similar colour pattern, but the pharyngeal tooth is not as long, and the blades of the compound chaetae have the teeth which are not as separated as in Syllis sp.

We cannot attribute this specimen to the genus Megasyllis since it does not have the segments divided into several sub-segments and the dorsal cirri are well articulated. So, we are not giving a formal name to this species currently.

Habitat. Intertidal.

Distribution. Australia (WA).

Figures

FIGURE 13. Syllis sp.A, anterior end, dorsal view. B, compound chaetae, anterior parapodium. C, compound chaetae, midbody parapodium. D, aciculae, anterior parapodium. E, aciculae, midbody. AM W.54220. Scale. A: 1 mm. B-E: 20 µm