Syllis patagonica, Soto & Martín & Lucas, 2020

Soto, Eulogio H., Martín, Guillermo San & Lucas, Yolanda, 2020, Three new species of Syllis Savigny in Lamarck, 1818 (Annelida, Syllidae) from Chilean Patagonia, Zootaxa 4878 (1), pp. 145-158 : 147-150

Syllis patagonica new species

Figures 2 , 3 , 4

Material examined. Holotype. St. 50 ( MNCN 16.01 /18723), 1 Paratype ( MNCN 16.01 /18724). St. 41, 1 Paratype ( MNCN 16.01 /18725) and 2 specimens used for SEM. St. 41, 5 Paratypes ( LBUV 001 /2020). St. 50, 5 Paratypes ( LBUV 002 /2020). Dates of collections: 19 October 2009 (St. 41) and 8 November 2010 (St. 50). Coordinates: St. 41 50°16’37” S 74°53’21’’W, St. 50 55º08´39.4” S 68º49´34.0” W.

Description. Body robust, with wide, well marked segments ( Figs 2A ; 3A ; 4A, B ) yellowish pale on alive specimens; anterior segments with one transversal dark brown slender stripe on middle and two lateral ones, slender and shorter, located posteriorly on each segment ( Fig. 3 A–D); color pattern easily disappears after fixation. Holotype complete, 8 mm long, 0.42 mm wide, 67 chaetigers. Prostomium subcircular, with two pairs of small eyes in open trapezoidal arrangement; median antenna similar in length to prostomium and palps together, inserted between posterior eyes, on posterior margin of prostomium, with about 11–13 articles; lateral antennae inserted in front of anterior eyes, near anterior margin of prostomium ( Figs 2A ; 4A, B ), slightly shorter than median antenna, with 10–11 articles. Peristomium slightly shorter than subsequent segments; dorsal tentacular cirri similar in length to median antenna, with 14-15 articles; ventral tentacular cirri shorter than dorsal ones, with 10 articles. Dorsal cirri shorter than body width, fusiform, thick ( Figs 2A , 3 A–D, 4A, B), dark by numerous glands inside articles; anterior dorsal cirri somewhat longer than remaining, with about 15-13-11-14-16 articles on first five chaetigers; dorsal cirri of proventricular segments with 8–11 articles, thicker than those of anterior segments; midbody dorsal cirri markedly fusiform and thick, alternating long ones with 10–11 and slightly shorter ones, with 8–9 articles ( Fig. 4C ). Parapodia conical, distally bilobed; ventral cirri short, thick, oval. Compound chaetae heterogomph falcigers with elongated, slender bidentate blades, proximal teeth small, distinctly smaller than distal ones, and short spines on margin, similar throughout, and marked dorsoventral gradation in length, more marked on anterior segments ( Fig. 2 B–D). Anterior parapodia each with 10–12 compound chaetae, blades 40 µm above, 18 µm below ( Figs 2B ; 4D ); midbody parapodia each with 8–10 compound chaetae, 38 µm above, 18 µm below ( Fig. 2C ); posterior parapodia each with 8–9 compound chaetae, 38 µm above, 13 µm below ( Fig. 2D ). Solitary dorsal capillary chaetae on posterior parapodia, slender, slightly bidentate ( Fig. 2E ); ventral simple capillary chaetae on far posterior segments, similar to dorsal one, slightly thicker ( Fig. 2F ). Anterior parapodia with four slender, pointed aciculae ( Fig. 2G ), three or four on midbody parapodia ( Fig. 2H ), and single in posterior parapodia, thicker than anterior and midbody ones, acuminate ( Fig. 2I ). Pharynx wide, through nine segments; pharyngeal tooth conical, on anterior margin. Proventricle similar in length to proventricle, through 10 segments, with 35 muscle cell rows and midline ( Fig. 2A ). Intestine clearly visible, with marked segmental caeca. Pygidium small, with two short anal cirri, with 11 articles.

Distribution. Only known from Chilean Patagonia. Concepción channel, Drumond Hay island and Ponsonby sound, Beagle channel ( Fig. 1 ).

Habitat. Inside tubes (non-empty and empty) of Chaetopterus cf. variopedatus , from boulders and sediment bottoms and associated to M. pyrifera holdfasts in fjords, islands and channels from Chilean Patagonia. Salinity: from 30.2 to 35 PSU, temperature: from 8.5 to 8.9°C. Shallow subtidal, between 14 and 30 metres depth.

Type locality. Concepción channel, Drumond Hay island, southern Chile (Patagonia) .

Remarks. Syllis patagonica , n. sp. is characterized by its color pattern (alive specimens), robust body with short, fusiform dorsal cirri whose articles are plenty of dark glandular inclusions, short, ovoid ventral cirri, and compound chaetae with elongated blades, similar throughout body, with short, small proximal tooth and short spines on margin. The arrangement of dorsal cirri is similar to those of Syllis armillaris (O. F. Müller, 1771) , a widely reported species but probably only inhabiting Atlantic European and Mediterranean coasts; however, S. armillaris has an elongated and slender body, the anterior chaetae are similar to those of S. patagonica n. sp. but those of midbody are different, with much shorter, almost unidentate blades ( Licher 1999; San Martín 2003). Syllis hyalina Grube, 1863 is also similar but the body is elongated and slender, the midbody dorsal cirri are more elongated, and the blades of compound chaetae are not so elongated as in S. patagonica n. sp., with blades more markedly bidentate ( Licher 1999; San Martín 2003). Syllis monilaris Savigny in Lamarck, 1818 , the type species of the genus, also has short dorsal cirri, but the body is also elongated, the dorsal cirri are slender than those of S. patagonica n. sp. and the compound chaeta are short and unidentate or almost unidentate ( Álvarez-Campos et al. 2015a; San Martín et al. 2017b). Syllis qamhiyn Lucas, San Martín & Fiege, 2020 , from Socotra (Indian Ocean), also has thickened, short dorsal cirri on midbody and short, ovoid ventral cirri, but the body is elongated and slender, the dorsal cirri ends more pointed, and the midbody and posterior chaetae have short blades ( Lucas et al. 2020). Finally, Syllis hampirmenyatu Martínez & San Martín, 2020 , from Timor, also has short dorsal cirri on midbody, but the body is slender and elongated, the dorsal cirri are not thick, and the compound chaetae have shorter blades ( Martínez & San Martín 2020).

There are additional species of Syllis having short, thickened dorsal cirri on the midbody, but they have partially or totally fused shafts with short blades.

Etymology. This species is named in honor of the Patagonian region currently considered a “Hotspot” of biodiversity, being type locality for many marine species.

Figures

FIGURE 1. Study area showing the sampling stations. Map modified from Google Earth©

FIGURE 2. Syllis patagonica n. sp. (Holotype, MNCN 16.01/18723). A, anterior end, dorsal view. B, compound chaetae, anterior parapodium. C, compound chaetae, midbody parapodium. D, compound chaetae, posterior parapodium. E, dorsal simple chaeta. F, ventral simple chaeta. G, aciculae, anterior parapodium. H, aciculae, midbody parapodium. I, aciculum, posterior parapodium. Scale: A, 0.2 mm; B–I, 20 µm.

FIGURE 3. Live specimens of Syllis patagonica n. sp. A–D, anterior end, dorsal view. Scale: A–D: 400 µm.

FIGURE 4. SEM of Syllis patagonica n. sp. A, anterior end, dorsal view. B, detail of prostomium and anterior segments, dorsal view. C, dorsal cirri and parapodia, midbody. D, anterior compound chaetae. Scale: A, 500 µm; B, 200 µm; C, 100 µm; D, 30 µm.