Syllis monilaris Savigny in Lamarck, 1818

Martín, Guillermo San, Álvarez-Campos, Patricia & Hutchings, Pat, 2017, The genus Syllis Savigny in Lamarck, 1818 (Annelida: Syllidae: Syllinae) from Australia (second part): four new species and re-description of twelve previously described species, Zootaxa 4237 (2), pp. 201-243 : 225-228

Syllis monilaris Savigny in Lamarck, 1818

Figures 14 , 15 , 16 A–C

Syllis monilaris Savigny in Lamarck, 1818: 318 ; Savigny 1822: 44 –45, pl. 4, fig. 3; Savigny 1826: 372 –373, pl. IV, fig. 3; Licher, 1999: 292; Álvarez-Campos et al. 2015b: 322 , figs 1–5.

Syllis moniliformis [sic; lapsus calami] Grube 1869: 502; Licher 1999: 306.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Houtman Abrolhos, NE entrance Goss Passage, Beacon Island , 28° 27' 54" S, 113° 46' 42" E, AM W.29492, 1 specimen, coll. 33 m, 25 May 1994, underneath boulders embedded in coral sand, by P. Hutchings.

Comparative material. EGYPT: El Tor (Sinai Peninsula, Gulf of Suez), C.G. Ehrenberg coll., id. A.E. Grube, 2 specimens: ZMB F1941, NEOTYPE ; ZMB 11529, 1 smaller specimen, broken in two pieces. ENGLAND, off Folkestone, eastern English Channel , 51° 27’ 26’’ N, 13° 03’ 79’’ E, coarse sediment with Sabellaria spinulosa reef, 33 m, 22 June 2014, Folkestone Pomerania Survey, 3 specimens (collection of APEM Ltd.).

Description. Body of large size, elongated ( Fig. 16 A), complete, 33 mm long, 1 mm wide, with 133 chaetigers, tapered posteriorly ( Fig. 16 A, C). Body opaque, dark, without colour pattern ( Figs 14 A, 16A). Prostomium pentagonal; 4 eyes in trapezoidal arrangement. Palps robust, similar in length to prostomium ( Fig. 14 A). Median antenna arising between posterior eyes, with 22 articles, slightly longer than combined length of prostomium and palps; lateral antennae shorter than median one, with 12–14 articles each. Peristomium shorter than subsequent segments ( Fig. 14 A). Dorsal tentacular cirri shorter than median antenna, with about 16 articles each; ventral tentacular cirri about half length of dorsal ones, with 12 articles each. Dorsal parapodial cirri similar or longer than body width on anterior segments, becoming similar to shorter than body width from midbody backwards, and more or less fusiform, especially from midbody backwards ( Figs 14 A–C, 16A–C), with well defined cirrophores and articles; articles basally and distally smaller than medially; anteriormost dorsal parapodial cirri longer than dorsal tentacular cirri, with 23–26 articles the longer ones, 16–17 the shorter ones ( Fig. 14 A); at the proventricular level, all dorsal parapodial cirri become shorter and similar in length, with about 10–16 articles ( Fig. 14 A, B), having 12-15 articles in midbody ( Fig. 14 C, B); in posteriormost segments, dorsal parapodial cirri with 10–14 articles each, being shorter and smaller than those of midbody, ( Fig. 14 D). Parapodia conical, distally bilobed on dorsal view ( Fig. 14 A). Ventral parapodial cirri digitiform, longer than parapodial lobes on anterior parapodia, becoming shorter from midbody onwards ( Fig. 14 B–D). Chaetae compound heterogomph falcigers, with thick shafts and short, triangular, unidentate blades, or very indistinctly bidentate with a minute proximal tooth, sometimes with short spines on margin but usually smooth or almost smooth and of similar shape and size throughout body ( Fig. 15 A–C). Usually dorsalmost falciger of each parapodium with slightly thicker shaft than remaining ones, especially in midbody ( Fig. 15 C). Anterior parapodia each with 9 compound chaetae, with blades slightly elongated, 57–39 µm long ( Fig. 15 A); midbody parapodia with 4–6 compound chaetae each, 43–34 µm long ( Fig. 15 B); posterior parapodia with 4–5 compound chaetae each, blades around 34 µm long ( Fig. 15 C). Dorsal and ventral simple chaetae not seen. Anterior parapodia each with 3–4 small aciculae, distally blunt ( Fig. 15 D); midbody parapodia with three aciculae, similar to those of anterior parapodia, but larger ( Fig. 15 E) two distally blunt and the rest slightly acuminate aciculae in each posterior parapodia ( Fig. 15 F). Pharynx extending through about 14 segments; pharyngeal tooth on anterior margin of pharynx. Proventricle through 13 segments; number of muscle cell rows not possible to count without dissection, since the body wall is quite opaque. Apparently, posterior part of body broken and regenerated ( Fig. 16 C).

Remarks. This specimen agrees perfectly with the description of the neotype ( Álvarez-Campos et al. 2015b), with small differences in size, number of articles of some cirri and other minor details. Distribution. Red Sea, Australia (Western Australia), English Channel; some previous dubious reports from the Mediterranean.

Figures

FIGURE 14. Syllis monilaris Savigny in Lamarck, 1818 (AM W. 29492). A, anterior end, dorsal view. B, anterior parapodium, lateral view. C, midbody parapodium, lateral view. D, posterior parapodium, lateral view. Scale bars: A: 0.4 mm. B – D: 0.2 mm.

FIGURE 15. Syllis monilaris Savigny in Lamarck, 1818 (AM W. 29492). A, compound chaetae, anterior parapodium. B, compound chaetae, midbody parapodium. C, compound chaetae, posterior parapodium. D, aciculae, anterior parapodium. E, aciculae, midbody parapodium. F, aciculae, posterior parapodium. Scale bars: A – F: 20 µm.

FIGURE 16. Syllis monilaris Savigny in Lamarck, 1818 (AM W. 29492). A, complete specimen. B, midbody, dorsal view. C, posterior end, dorsal view. Syllis nigropunctata Haswell, 1886 (AM W. 29505). D, anterior end, dorsal view. E, prostomium and most anterior segments.