Syllis gantheaumensis ( Hartmann-Schröder, 1979 ) Martín & Lucas & Hutchings, 2024

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 : 4-6

Syllis gantheaumensis ( Hartmann-Schröder, 1979) , n. comb.

Figure 3

Typosyllis (Typosyllis) filidentata gantheaumensis Hartmann-Schröder, 1979: 91 , figs. 73-76; 1981: 26.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberley region , Broome, Gantheaume Point, coll. G. Hartmann-Schröder, 9 Sept 1975, coralligene, eulittoral ZMH-P-0015467, Holotype.

Additional material examined. Typosyllis filidentata Hartmann-Schröder,1962 . ARGENTINA, Santa Cruz, Magallanes, Puerto San Julián, coll. G. Hartmann-Schröder 2 Nov 1960, ZMH-P-0014660, Holotype.

Description. Holotype incomplete specimen, 2.75 mm long, 0.4 mm wide, 53 chaetigers. Body wide, without colour markings. Prostomium oval, with two pairs of small eyes in open trapezoidal arrangement not seen (fide Hartmann-Schröder, 1979) (probably unpigmented after years in alcohol). Palps shorter than prostomium. Median antenna inserted in middle of prostomium, with 15 articles (22 fide Hartmann-Schröder, some articles probably lost), longer than combined length of prostomium and palps; lateral antennae originating near anterior margin of prostomium, markedly shorter than median antenna, with 13 articles ( Fig. 3A ). Peristomium shorter than subsequent segments; dorsal tentacular cirri similar in length to median antenna, with 17–19 articles; ventral cirri with about 9–11 articles. Dorsal cirri of first chaetiger long, with more than 20 articles ( Fig. 3A ); dorsal cirri markedly coiled, relatively short, alternating long and short ( Fig. 3B ); long cirri of midbody with about 22 articles, short cirri with 13 articles; articles full of spiralized glands ( Fig. 3A, B ), making dorsal cirri dark. Parapodia bilobed. Ventral cirri digitiform. Compound chaetae all bidentate falcigers, distally slightly hooked and acute, and proximal teeth very slender and short, with moderately long, curved spines on margin on basal part becoming gradually shorter distally ( Fig. 3C–E ). Anterior parapodia with 7–8 chaetae, blades 28 µm above, 13 µm below ( Fig. 3C ); midbody parapodia with 6–7 chaetae, blades 33 µm above, 16 µm below ( Fig. 3D ); posterior parapodia with 4–5 compound chaetae similar to those of midbody, 30 µm above, 15 µm below ( Fig. 4E ). Spines on margin of compound chaetae, proportionally longer in long blades. Dorsal simple chaetae on posterior segments, fine, distally with thin spines on margin and slightly bidentate ( Fig. 3F ). Ventral simple chaetae not seen. Anterior parapodia with three thin aciculae, one straight and two slightly curved distally ( Fig. 3G ); midbody with two aciculae ( Fig. 3H ); posterior parapodia with solitary, acuminate acicula ( Fig. 3I ). Pharynx long and slender, partially everted, through 13 segments ( Fig. 3A ); pharyngeal tooth on anterior margin of pharynx. Proventricle also long, through 11 segments, with 33 muscle cell rows.

Remarks. Hartmann-Schröder (1979) described it as a subspecies of Typosyllis filidentata , described from Patagonia, Argentina, as she regarded the proximal teeth of the Australian specimens as filiform. However, we do not consider them as filiform; they are very thin and short, but straight. Also, the blades of the compound chaetae have longer spines on margin, which however in the Argentinian species are very short. The holotype of the T. filidentata is in very poor condition, but we could observe that the chaetae have short spines. So, we consider them as two different species.

Syllis gantheaumensis , n. comb. is very similar to S. hyalina Grube, 1863 , and S. armillaris (O. F. Müller, 1776) also reported from Australia. However, they seem to be different species, since this species has proportionally longer dorsal cirri and longer spines on margin of compound chaetal blades.

Habitat. Coralligenous algae, eulittoral.

Distribution. Only known from the type-locality.

Figures

FIGURE 3. Syllis gantheaumensis (Hartmann-Schröder, 1979), n. comb. A, anterior end, dorsal view. B, long and short midbody dorsal cirri. C, compound chaetae, anterior parapodium. D, compound chaetae, midbody parapodium. E, compound chaetae, posterior parapodium. F, dorsal simple chaeta. G, aciculae, anterior parapodium. H, aciculae, midbody parapodium. I, acicula, posterior parapodium. ZMH-P-0015467. Scale. A: 0.2 mm; B, 0.1 mm, C-I: 20 µm.

FIGURE 4. Syllis heronislandensis (Hartmann-Schröder, 1991) n. comb.A, anterior end, dorsal view. B, long and short dorsal cirri from midbody. C, compound chaetae, anterior parapodium. D, compound chaetae, midbody parapodium. E, compound chaetae, posterior parapodium. F, dorsal simple chaeta. G, ventral simple chaeta. H, aciculae, anterior parapodium. I, acicula, midbody parapodium. J, acicula, posterior parapodium. AM W.54219. Scale. A, B: 0.1 mm. D-J: 20 µm.