Syllis mercedesae, Lucas, Yolanda, Martín, Guillermo San & Parapar, Julio, 2012

Lucas, Yolanda, Martín, Guillermo San & Parapar, Julio, 2012, Two new species of Syllidae (Annelida: Polychaeta) from DIVA-Artabria I project (cruise 2002) to deep areas off NW Spain, Zootaxa 3589, pp. 77-88 : 83-86

Syllis mercedesae sp. nov.

Figures 5–6 , Table 1

Type material: A total of 8 specimens were obtained from three DIVA-Artabria I samples. Sample AT-1000, holotype ( MNCN 16.01/12018) and 5 paratypes ( MNCN 16.01/12021-25). Sample AT-600, 1 paratype, 11/09/ 2002, 629– 631 m, nodules and stones, 43º53.457’N; 08º48.461’W ( MNCN 16.01/12019). Sample DRN-800, 1 paratype, 11/09/2002, 827– 819 m, stones, 43º51.265’N; 08º54.480’W ( MNCN 16.01/12020).

Diagnostic characters: Midbody parapodia with straight aciculae and moderately long spiniger-like chaetae having indistinct subdistal tooth and appearing almost unidentate.

Description based on holotype: Body long, thin; holotype 15 mm long, 0.5 mm wide, 72 chaetigers; longest specimen 20 mm long, 1 mm wide, 94 chaetigers. Prostomium semicircular to pentagonal, with four eyes in trapezoidal arrangement, anterior eyes larger than posterior; apparently without eyespots ( Figs. 5 A, B). Median antenna longer than prostomium and palps together, inserted between posterior eyes with 12–14 articles ( Fig. 5 B); lateral antennae inserted near anterior margin of prostomium, similar in shape to median antenna, with 12 articles. Peristomium somewhat shorter than subsequent segments; dorsal tentacular cirri long, with 17–23 articles; ventral cirri shorter than dorsal ones with about 10 articles. First dorsal cirri longer than remaining ones (20–26 articles), then alternating short (11–12 articles) and long (17–18 articles), becoming progressively shorter and fusiform after proventricle, with 8–9 articles, at midbody to 7–8 articles in posterior-most cirri ( Figs. 5 A–C). Anterior parapodia with 10–14 compound heterogomph chaetae; dorsal-most ones with relatively long blades (70 µm long) with short marginal spines, slightly bidentate ( Fig. 6 A); remaining chaetae with shorter blades, decreasing progressively in length from dorsal (27–28 µm long) to ventral (22 µm long), with short marginal spines and distinct subdistal tooth ( Fig. 6 B). Number of compound chaetae per parapodium progressively decreasing to 8 from midbody: 1–2 dorsal, with elongated blades (70 µm long), spiniger-like, bidentate, with subdistal tooth small, and short marginal spines ( Figs. 6 D, E); remaining chaetae with marked dorsoventral gradation in blade length (from 40 to 20 µm), bidentate. Posterior parapodia with 8 compound chaetae, one with slightly elongated blade (44 µm long) and short marginal spines, bidentate, with subdistal tooth distinct ( Fig. 6 G); remaining chaetae with shorter articles (27–28 µm to 19–20 µm long), with short marginal spines and distinct subdistal tooth ( Fig 6 H). Dorsal simple capillary chaeta on posterior parapodia, bidentate, smooth ( Fig. 6 I). Ventral simple chaeta on posterior parapodia, slender, bidentate, with subdistal tooth small, smooth ( Fig. 6 J). Anterior parapodia with four aciculae, three of them thin, with straight, blunt tips; one with truncate tip ( Fig. 6 C); then progressively decreasing to two at midbody ( Fig. 6 F) and one in posterior parapodia, straight, acute distally, protruding from parapodial lobes ( Fig. 6 K). Pygidium small, with two long anal cirri with 14 articles ( Fig. 5 C). Pharynx long and slender, through about nine segments ( Fig. 6 A); middorsal pharyngeal tooth located on anterior margin. Proventricle shorter than pharynx, through seven segments with about 27–28 muscle cell rows.

Etymology: The species is named after Mercedes Lucas Rodríguez, sister of first author.

Type locality: Continental slope off Ártabro Gulf (Galicia, NW Spain), on hard substrates (dead corals and stones), from 1091 to 1132 m deep.

Remarks. Thirty two species of Syllis are currently known for the Iberian Peninsula ( San Martín 2003; Del Pilar Ruso & San Martín 2012), none combining the presence of straight aciculae, protruding from parapodial lobes in posterior-most parapodia with the midbody moderately long spiniger-like chaetae with indistinct subdistal tooth, appearing almost unidentate. The new species resembles Syllis parapari San Martín and López, 2000 ( San Martín & López 2000) , but the pseudo-spiniger chaetae in Syllis mercedesae sp. nov. have shorter articles and indistinctly bidentate distal ends; the posterior dorsal and ventral simple chaetae are bidentate, smooth (with broad tip and spinulated in S. parapari ); the dorsal cirri are somewhat thicker and less sharpened distally (more elongated and sharpened in S. parapari ); and, finally, the 6–8 anterior aciculae differ in shape in both species. Syllis beneliahuae Campoy and Alquézar, 1982 ( Campoy & Alquézar 1982) also resembles the new species in having falciger chaetae very similar in shape, but differs in the acicular shape (slender, acuminate in S. beneliahuae ; straight, acute, protruding out of the parapodia in S. mercedesae sp. nov.) The spiniger-like chaetae of the new species are similar to those of Syllis rosea ( Langerhans, 1879) , but differs in their length and, also, in the shape of its posterior aciculae (broad, ending in right angle in S. rosea ). Syllis cornuta Rathke, 1843 (species wrongly reported in the Iberian Peninsula) differs from S. mercedesae sp. nov. in having longer, slender dorsal cirri, as well as in some chaetal details. The differences among all these species in blade length of pseudospiniger chaetae, together with some other relevant characters are summarized in Table 1 . Furthermore, no other species of the genus worldwide ( Licher 1999) has the peculiar combination of characters of S. mercedesae sp. nov., allowing the description of a new species.

Figures

FIGURE 5. Syllis mercedesae sp. nov. A. Anterior end dorsal view; B. Prostomium, dorsal view (paratype); C. Pygidium dorsal view. Scale: 0.38 mm.

FIGURE 6. Syllis mercedesae sp. nov. A, B. Anterior compound chaetae; C. Anterior aciculae; D and E. Midbody compound chaetae; F. Midbody aciculae; G and H. Posterior compound chaetae; I. Posterior dorsal simple chaeta; J. Posterior ventral simple chaeta; K. Posterior acicula. Scale: 20 μm.