Syllis antoniae, Salcedo, Diana L. & Solís-Weiss, Guillermo San Martín And Vivianne, 2012

Salcedo, Diana L. & Solís-Weiss, Guillermo San Martín And Vivianne, 2012, The genus Syllis (Polychaeta: Syllidae: Syllinae) in the southern Mexican Pacific, with the description of two new species and three new records, Zootaxa 3263, pp. 47-62 : 51-54

Syllis antoniae n. sp.

( Figs 1 A–C, 2A–F, 3A–F)

Material examined. 76 specimens: Holotype complete specimen (CPICML POH-37-005), Palmitas, E2B1 16°49.420’N, 99°54.733’W, 25 May 2006, 10.5 m, coarse sand. Paratypes: 15 specimens (CPICML POP-37-006), Palmitas, E2B1 16°49.420’N, 99°54.733’W, 25 May 2006, 10.5 m, coarse sand. 15 specimens ( MNCN 16.01/ 13252), Palmitas E2B2, 16°49.420’N, 99°54.733’W, 25 May 2006, 10.5 m, coarse sand. 15 specimens ( NHMLA LACM-AHF Poly 3032), 15 specimens (AM W38809), Palmitas, E2B1 16°49.420’N, 99°54.733’W, 25 May 2006, 10.5 m, coarse sand. 15 specimens, Caleta E1B2, 16°49.797’N, 99°54.062’W, 25 May 2006, 12 m, coarse sand.

Additional material. 240 specimens (CPICML PO-37-082): 59 specimens, Caleta E1B1, 16°49.797’N, 99°54.062’W, 25 May 2006, 12 m, coarse sand. 79 specimens, Caleta E1B2, 16°49.797’N, 99°54.062’W, 25 May 2006, 12 m, coarse sand. 41 specimens, Palmitas E2B1, 16°49.420’N, 99°54.733’W, 25 May 2006, 10.5 m, coarse sand. 57 specimens, Palmitas E2B2, 16°49.420’N, 99°54.733’W, 25 May 2006, 10.5 m, coarse sand. 2 specimens, El Jardín E3B1, 16°49.436’N, 99°54.981’W, 26 May 2006, coarse sand. 2 specimens, El Jardín E3B2, 16°49.436’N, 99°54.981’W, 26 May 2006, coarse sand.

Comparative material examined. Syllis prolifera , 1 specimen ( MNCN 16.01/8287). SPAIN: Mediterranean Sea, Chafarinas Is., Is. S. Isabel II Island, 0.5 m. Syllis prolifera 1 specimen ( MNCN 16.01/4383). SPAIN: Mediterranean Sea, Denia, Alicante. Syllis vivipara , 1 specimen ( MNCN 16.01/11264). CUBA: Caribe, Antonio Beach, Guanahacabibes Peninsula, Pinar del Rio, 1.5 m.

Description. Holotype complete, 8 mm long, 0.35 mm wide, 69 chaetigers. Longest complete specimen, 11.1 mm long, 0.3 mm wide, 79 chaetigers. Body medium to large, elongate, cylindrical, without a distinctive color pattern. Prostomium trapezoidal, longer than wide, laterally bilobed, anterior part distinctly longer ( Fig. 1 A). Two pairs of eyes in trapezoidal arrangement, one pair per lobe ( Fig. 1 A). Dorsum with a rough surface and numerous minute pores, visible under SEM ( Fig. 2 B). A pair of ciliated nuchal grooves extending along postero-lateral margin, between prostomium and peristomium ( Figs 1 A, 2A). Palps triangular, as long as prostomium. Antennae, and tentacular and dorsal cirri slender and thin, basally weakly articulated, containing amber fibrillar material in each article, resulting in a dark appearance. Median antenna much longer than prostomium and palps together, with about 43–45 articles, arising between anterior pair of eyes; lateral antennae somewhat shorter than median one, with about 25 articles, originating in front of anterior pair of eyes ( Figs 1 A, 2A). Peristomium well differentiated, slightly extended anteriorly, partially covering posterior part of prostomium and forming a cavity where nuchal organs are located ( Fig. 2 A); two pairs of tentacular cirri, dorsal pair similar to median antenna, with about 48–51 articles, ventral pair shorter, with about 19–22 articles. Dorsal cirri longer than body width, with irregular variations in length on anterior part (first pair with 58 articles, second with 28–31 articles, third with 40 articles, fourth with 44–45 articles, fifth with 27–28, sixth with 59–66, seventh with 21–22 articles, eight with 42–44, ninth with 34 articles, tenth with 27–28 articles) and alternating in length in midbody and posterior part; from proventricle backwards, long dorsal cirri with about 37–63 articles and shorter ones with 20–30 articles, diminishing in length posteriorly. Ventral cirri short, digitiform, not extending beyond parapodial lobes (approximately half of their length). Parapodial lobes relatively long, broad, distally bilobed ( Fig. 1 A) (more evident towards posterior end). Eight to ten compound chaetae per parapodium, up to four chaetae in the most posterior chaetigers. All falcigers heterogomph, bidentate, with the subdistal tooth smaller, sometimes indistinct, similar throughout. Superior and medium falcigers with both teeth distinguishable, former with short and uniform marginal spinulation, latter with coarse and long spines on basal margin ( Fig. 1 B); most inferior chaetae with an indistinct subdistal tooth (that could be confused with a small spine) and inconspicuous marginal spinulation ( Fig. 3 C). Strong dorso-ventral and antero-posterior gradation in subdistal teeth size and in length of blade; blades of anterior falcigers longer and thinner (between 14.8 and 20 Μm) ( Fig. 1 B) and progressively diminishing in length, becoming broader and diminishing in subdistal tooth size ( Fig. 3 A, 3C). Solitary dorsal simple chaeta on posterior chaetigers, broad, unidentate, with short and fine subdistal marginal spines ( Figs 2 E, 3E); ventral simple chaetae thin, bidentate, with two small teeth separated ( Figs 2 F, 3F). Two rounded and distally hollow aciculae in anterior parapodia ( Fig. 1 C), one in midbody ( Fig. 3 B) and posterior parapodia ( Fig. 3 D). Pharynx long and broad, extending throughout 6–7 segments, a conical tooth slightly back from anterior margin ( Fig. 1 A). Proventricle relatively short and broad, extending through 5 segments, with about 25 muscle cell rows ( Fig. 1 A). Pygidium rounded, with a digitiform median stylus and two long anal cirri, with about 22 articles.

Remarks. Syllis antoniae n. sp., is characterized by bidentate compound chaetae (some with coarse and large spines on basal margin and with a small subdistal tooth) and by dorsal and tentacular cirri distinctly slender. This species is closely related to Syllis vivipara Krohn, 1869 which has been recorded from the Mediterranean Sea, the Atlantic Ocean and the Caribbean Sea, and to Syllis prolifera Krohn, 1952 , which seems to be found in circumtropical and temperate areas, and also to Syllis rubicunda Aguado, San Martín and Nishi, 2008 , recorded on the Japanese coasts. In all these species the same kind of aciculae, similar chaetal arrangement and a pharyngeal tooth slightly back from anterior margin are present. Nonetheless, S. vivipara has hooked chaetae and some unidentate chaetae, where the subdistal tooth disappears completely; additionally, the spinulation of the chaetae is shorter and more uniform than in S. antoniae n. sp., which has a shorter pharynx and dorsal cirri and a proventricle with more rows of muscular cells (about 40). Syllis prolifera and S. rubicunda have distinctly bidentate falcigers, with both teeth similar in size and spinulation shorter and uniform, bidentate dorsal simple chaetae and a peristomium extending forward, partially covering the prostomium. Additionally, S. rubicunda has broad dorsal cirri and a distinctive red or orange pattern on the dorsum.

Habitat. Coarse sand, subtidal.

Distribution. Western coast of Acapulco Bay, Southern Mexican Pacific.

Etymology. The species is named in honor of María Antonia Oropeza, first author’s mother.

Figures

FIGURE 1. Syllis antoniae n. sp. (A) Anterior end, dorsal view. (B) Anterior chaetae. (C) Anterior aciculae. Scale 40 µm.

FIGURE 2. SEM of Syllis antoniae n. sp. (A) Anterior end, dorsal view. (B) Detail of dorsum (pores). (C) Superior chaetae, anterior chaetiger. (D) Median and most inferior chaetae, anterior chaetiger. (E) Dorsal simple chaeta. (F) Ventral simple chaeta. Scale: (A) 50 µm. (B, D) 10 µm. (C, E – F) 5 µm.

FIGURE 3. Syllis antoniae n. sp. (A) Midbody chaetae. (B) Midbody aciculae. (C) Posterior chaetae. (D) Posterior aciculae. (E) Dorsal simple chaeta. (F) Ventral simple chaeta.