Syllis similisunzima, 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 : 282-285

publication ID 10.11646/zootaxa.5230.3.1

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scientific name

Syllis similisunzima

sp. nov.

Syllis similisunzima View in CoL n. sp.

Figures 17 View FIGURE 17 , 18 View FIGURE 18

Material examined. AUSTRALIA. NEW SOUTH WALES: NSW 3382 , Pittwater, pontoon 400 m east of The Basin, 33° 36’ 09” S, 151° 17’ 49” E, coll. 4 May 2009, 11.9 m, hand collected on SCUBA, scraping of pontoon, Holotype AM. W.35404; Sydney Harbour , White Bay Berth 3, 33° 51’ 47” S, 151° 11’ 00” E, coll. 5 March 2009, 11.8 m, hand collected on SCUBA, scraping of wharf, AM W.53806, 5 paratypes. GoogleMaps

Diagnosis. Single transversal, purple to brown, band on anterior segments; double band from segments anterior to proventricle backwards. Dorsal cirri long and slender, alternating in length in midbody. Compound chaetae bidentate falcigers, with small proximal tooth and short spines on margin. Posterior aciculae distally rounded, apparently hollow on tips. Pharyngeal tooth located back from anterior margin of pharynx.

Description. Longest complete paratype, broken into two pieces, 7 mm long, 0.47 mm wide, 61 chaetigers. Holotype smaller, an anterior part with regenerating posterior end, 4.2 mm long, 31 chaetigers. Body of medium size, elongate, cylindrical, with a distinctive colour pattern, anterior segments dorsally dark, each segment with a purple to brown or reddish band, anteriorly less marked; from proventricle onwards two slender transverse bands, anterior larger and less marked, posteriorly thin and darker; from midbody, only one thin transverse band, present just before intersegmental furrow, and some scattered spots of pigment dorsally on segments ( Fig. 17A View FIGURE 17 ), or forming two rows, anterior light and posterior darker; some scattered pigment on prostomium. Prostomium oval, with two pairs of red eyes in trapezoidal arrangement and pair of anterior eyespots ( Fig. 17A View FIGURE 17 ). Palps triangular, as long as prostomium. Antennae, tentacular and dorsal cirri slender and distinctly articulated ( Fig. 17A, B View FIGURE 17 ). Median antenna much longer than prostomium and palps together, with about 37 articles, arising between posterior pair of eyes; lateral antennae distinctly shorter than median one, about half the length, with about 30–32 articles, originating in front of anterior pair of eyes ( Fig. 17A View FIGURE 17 ). Peristomium shorter than subsequent segments; dorsal tentacular cirri similar to median antenna, with about 30 articles, ventral pair shorter, with about 18 articles. Dorsal cirri longer than body width, longer on anterior segments, with about 40, 15, 34, 37 articles on first four segments, and alternating in length in midbody and posteriorly, with about 36 articles longer, 20 articles shorter ones ( Fig. 17B View FIGURE 17 ), diminishing in length posteriorly. Ventral cirri short, digitiform, not extending beyond parapodial lobes. Parapodial lobes distally bilobed ( Fig. 17A View FIGURE 17 ). All falcigers heterogomph, bidentate with proximal tooth small, distally hooked, with long, thin spines on margin, numbering 7–8 per parapodium throughout; slight dorso-ventral gradation on anterior parapodia ( Fig. 18A View FIGURE 18 ), 40 µm above, 25 µm below; compound chaetae of midbody all similar ( Fig. 18B View FIGURE 18 ), broader than those of anterior segments, 33 µm above, 25 µm below; posterior compound chaetae ( Fig. 18C View FIGURE 18 ) with smaller blades, 23–16 µm. Dorsal simple chaeta on posterior chaetigers, slender, subdistally spinulated, finely bidentate ( Fig. 18D View FIGURE 18 ); ventral simple chaetae thin, sinuous, finely bidentate ( Fig. 18E View FIGURE 18 ). Three aciculae in each anterior parapodium, distally rounded, difficult to see ( Fig. 18F View FIGURE 18 ), two in midbody, distally rounded and hollow ( Fig. 18G View FIGURE 18 ) and solitary in midposterior and posterior parapodia, distally hollow ( Fig. 18H View FIGURE 18 ). Pharynx long, extending through 8–10 segments; large, conical tooth distinctly distant to anterior margin ( Fig. 17A View FIGURE 17 ). Proventricle similar in length to pharynx, extending through 6–8 segments, with about 40–48 muscle cell rows, with midline ( Fig. 17A View FIGURE 17 ). Pygidium rounded, with a digitiform median stylus and two long anal cirri, with about 40 articles.

Remarks. Syllis similisunzima n. sp. is very similar to Syllis unzima Simon, San Martín & Robinson, 2014 , from South Africa; both have similar colour pattern, size, shape of dorsal cirri, bilobed parapodial lobes, long and distinct pharyngeal tooth located distally from anterior margin of pharynx, and compound chaetae with slightly hooked blades. However, S. similisunzima n. sp. has darker pigmentation on anterior segments, the transverse row of pigment on midbody and posterior segments is just in front of the subsequent intersegmental furrow, not after, as happens in S. unzima , the blades of compound chaetae in S. similisunzima are bidentate (although the proximal tooth is small), whereas they are unidentate in S. unzima , the anterior chaetae in S. similisunzima are longer than those of S. unzima , the compound chaetae of S. unzima have longer spines on the margin than those of S. similisunzima , and finally, S. similisunzima has a longer proventricle than S. unzima , with more muscle cell rows and a marked midline, which is lacking in S. unzima .

Furthermore, S. unzima is a viviparous species living associated with sea cucumbers of the genus Holothuria ; none of the specimens of S. similisunzima shows any sign of viviparity, and they are free living.

Etymology. The species is named after its similarity to Syllis unzima Simon, Robinson & San Martín, 2014 ; similis is a latin word that means “similar to”.

Habitat. Scrapings of pylons in 12 m depth.

Distribution. Australia (NSW).


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