Syllis truncata Haswell, 1920

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 : 287-289

Syllis truncata Haswell, 1920

Figure 20

Syllis truncata Haswell, 1920: 94 , pl. 10, figs 7–14.

Typosyllis truncata .— Licher 1999: 160, pl. 71.

Typosyllis subterranea .— Hartmann-Schröder, 1962: 93, Figs 72–74; 1965b: 288.

Material examined. AUSTRALIA, QUEENSLAND: 01- Liz 52-2, Outer Yonge Reef, Great Barrier Reef , 14°36’ S, 145°38’E, coll. 24 Jan 1977, 30 m, hand collected on SCUBA, coral rubble, AM W.53808, 6 specimens . NEW SOUTH WALES: Boat Harbour, south of Port Stephens , 32° 46’ 59” S, 152° 06’ E, coll. 14 March 2006, hand collected on snorkel, in amongst Galeolaria caespitosa, AM W. 53811, 4 specimens . Newport , 33° 39’ S, 151° 19’ E. coll. 22 Jul 2005, intertidal rock pools in Corallina sp. , AM. W.53810, 1 specimen . NSW 3399 , Sydney Harbour, White Bay Berth 3, 33° 51’ 47” S, 151° 11’ 00” E, coll. 05 March 2009, 11.8 m, hand collected on SCUBA, scraping on wharf piles, AM W.53812, 3 specimens . WESTERN AUSTRALIA: St. 21, Ningaloo Reef , 22° 17’ 00” S, 118° 48°, coll. 19 June 2008, intertidal algal turf, AM W.53809, 2 specimens . St. 50, Kimberley region, East Montalivet Island , 15° 06’ S, 15° 06’ S, coll. 15 July 1988, intertidal, AM W.53813, 1 specimen .

Additional material examined. AUSTRALIA, NEW SOUTH WALES. Port Jackson , Lectotype, AM W 506 .

Diagnosis. Segments wide and short. Dorsal cirri similar in length to body width or shorter. Compound chaetae with few, usually one, dorsal falcigers with blade bidentate and short spines on margin, slender and longer than remaining, distally broad; remaining chaetae with shorter blades, bidentate and moderately long spines on margin. Dorsal simple chaetae truncate. Posterior aciculae with tip ending in right angle.

Description. Longest complete specimen 10 mm long, 0.5 mm wide, with 114 chaetigers. Body relatively long, thick, with wide and short, well-marked segments, without colour pattern (up to 20 mm long, 120 chaetigers, reddish when alive, according to Haswell 1920); small specimens much more slender, filiform. Prostomium rectangular; four eyes in trapezoidal arrangement. Palps broad, similar in length to prostomium ( Fig. 20A ). Median antenna arising between posterior eyes, with 20–23 articles, almost twice as long as combined length of prostomium and palps; lateral antennae shorter than median one, with 15–17 articles. Peristomium dorsally distinctly shorter than subsequent segments ( Fig. 20A ). Dorsal tentacular cirri similar in length to, or slightly longer than, median antenna, with about 22 articles; ventral tentacular cirri about 2/3 as long as dorsal ones, with 13–14 articles. Dorsal parapodial cirri shorter than body width, with well marked articles; distinct, large, hyaline inclusions inside the dorsal parapodial cirri, especially from proventricular segments onwards ( Fig. 20A ), alternating long and short, no marked difference of length, with about 22 articles long ones, 15 articles on short ones in midbody ( Fig. 20A ). Parapodia conical. Ventral parapodial cirri digitiform, shorter than parapodial lobes. Compound chaetae of each parapodium with 1–2 dorsalmost chaetae provided with distinctly longer and slender blades, distally rounded on tip, and small proximal tooth, close to distal one, straight or slightly curved, and moderate spines on margins ( Fig. 20B, C, D , left), 28μm on anterior parapodia, somewhat longer, 32 μm on midbody and posterior parapodia, and about 8–10 chaetae with shorter blades, distally acute, with proximal tooth smaller than distal one, longer spines on margin, and dorso-ventral gradation in length, 21–13 µm long on anterior parapodia, 25–14 µm on midbody and posterior parapodia. Blades of remaining chaetae of each parapodium with more separated teeth and longer spines on margin ( Fig. 20B, C, D ), and dorsoventral gradation in length. Dorsal simple chaetae only on posterior parapodia, distally truncate ( Fig. 20E ). Ventral simple chaetae only on far posterior segments, minute, apparently unidentate, only seen on one specimen.Anterior parapodia with two slender aciculae each, distally rounded ( Fig. 20F ), reducing to one on midbody and posterior parapodia, distally ending in right angle ( Fig. 20G ). Pharynx long, extending through about 11 segments; pharyngeal tooth elongated, conical, acute, on anterior margin of pharynx ( Fig. 20A ). Proventricle similar in length to pharynx, through eight segments, with about 30 muscle cell rows. Pygidium with two anal cirri, and a median stylus.

Remarks. Syllis truncata belongs to a group of species with truncate dorsal simple chaeta and posterior aciculae ending in right angle (foot-like). Some Australian species of this group are S. albanyensis ( Hartmann-Schröder, 1984) , S. erikae ( Hartmann-Schröder, 1981) , S. macrodentata ( Hartmann-Schröder, 1982) , S. rosea ( Langerhans, 1879) , S. edensis ( Hartmann-Schröder, 1989) , were redescribed in the two previous papers on Australian Syllis (Álvarez-Campos et al. 2015, San Martín et al. 2017) as well as S. pharynxcircunfusata ( Hartmann-Schröder, 1979) (see above). Other species of this group are the European species S. amica Quatrefages, 1865 , S. kabilika BenEliahu, 1977 , S. pulvinata ( Langerhans, 1881) , S. cryptica Ben-Eliahu, 1977 , S. thyrrena (Licher & Kuper, 1998) (see San Martín, 2003) (some also described or reported from other areas). The species of this group in which the sexual stolon is known have the Tetracerous type.

The examined specimens agree with Haswell’ type specimen; such specimen was previously examined by BenEliahu (1977) and was also redescribed by Licher (1999).

Habitat. Coral rubble, amongst serpulids, algae. Intertidal and subtidal.

Distribution. Australia (QLD, NSW).

Figures

FIGURE 20. Syllis truncata Haswell, 1920. AM W.53811. A, anterior end, dorsal view. B, falcigers, anterior parapodium. C, falcigers, midbody parapodium. D, falcigers, posterior parapodium. E, dorsal simple chaeta. F, aciculae, anterior parapodium. G, acicula, posterior parapodium. Scale. A: 0.2 mm. B–G: 20 µm.