Exogone martinsosai, Núñez & Martín, 2024

Núñez, Jorge & Martín, Guillermo San, 2024, Syllidae Grube, 1850 (Annelida) from Conception, Amanay and Banquete Banks off Canary Islands, with the description of two new species, Zootaxa 5477 (1), pp. 43-65 : 50-52

Exogone martinsosai n. sp.

Figure 2

Material examined. INCOECO station: BC3 0611, 645 m depth, Holotype ( MNCN 16.01 /18955) ; INFUECO station: BC5 0710, 2 Paratypes ( MNCN 16.01 /18956), 237 m depth. Additional material . INFUECO station: BC6 0611, 1 specimen, 254 m depth.

Description. Body long, slender, filiform; Holotype incomplete, 3.7 mm long, 0.1 mm wide, 38 chaetigers; longest Paratype complete, 6 mm long, 55 chaetigers. Prostomium ovate to subrectangular, wider than long; apparently without eyes (probably lost after fixation). Antennae apparently lost; holotype with a short, ovate median antenna and one paratype with a similar lateral antenna, all similar in length. Palps broad, longer than prostomium, fused along their length, with a distinct dorsal notch. Peristomium shorter than subsequent segments; tentacular cirri ovoid, small. Dorsal cirri similar to tentacular cirri but longer, shorter than parapodial lobes, absent on chaetiger 2 ( Fig. 2A ). Anterior three parapodia each with about 6–7 compound falcigers, with spinose shafts and somewhat elongated, bidentate blades, subdistal tooth long and minute, indistinct distal tooth, with fine, moderately long marginal spines, 10 μm long, without compound spiniger-like chaetae ( Fig. 2B ). From about chaetiger four, parapodia each with solitary spiniger-like chaeta, shaft enlarged, distally expanded, with numerous spines, and proportionally short, thin, unidentate, filiform, triangular on bases blade, appearing like a long spine under low magnifications, apparently smooth, 35–40 μm long ( Fig. 2C, E ); in addition, 5–6 (4- 3 in midbody) falcigers, similar to those of anteriormost parapodia but slightly shorter ( Fig. 2D, F ); posterior parapodia each with solitary compound spiniger-like chaetae similar to those of midbody segments ( Fig. 2G ); in addition, three falcigers with short blades, 7–8 μm long ( Fig. 2H ). Dorsal simple chaetae from chaetiger 1, with rounded tips and finely spinulose subterminally, thicker posteriorly ( Fig. 2I–L ). Ventral simple chaetae on most posterior parapodia, thick, sigmoid, smooth, bidentate, with small distal tooth and large subdistal tooth ( Fig. 2M ). A single aciculae per parapodium along the body, slender, distally rounded, apparently hollow in tip ( Fig. 2N ). Pharynx long, everted in all specimens, through about five segments; pharyngeal tooth long, on anterior rim ( Fig. 2A ). Proventricle similar in length to pharynx, through four segments, with 15 very thick muscle cell rows ( Fig. 2A ). Pygidium with 2 long anal cirri.

Remarks. Exogone martinsosai n. sp. belongs to a group of this genus sharing some characters, having shafts of spiniger-like compound chaetae distally enlarged, spinose and blades relatively short, triangular, which are absent on most anterior segments, and absence of dorsal cirri on the second chaetiger. The related species are Exogone heterosetosa McIntosh, 1885 , from sub-Antarctic seas, Philippines and Australia ( San Martín 2005; San Martín et al. 2021), E. heterosetoides Hartmann-Schröder, 1979 from Australia, New Zealand, Philippines, and southern areas of Chile ( San Martín 2005; San Martín et al. 2021), and E. mompasensis Martínez, Adarraga & San Martín, 2002 , which is known only from the type locality Mompás (Guipúzcoa, Spain) ( Martínez et al. 2002; San Martín 2003). The new species, Exogone martinsosai n. sp., has an appreciable smaller thickening of the distal end of the shaft of the spiniger-like chaetae, similar to E. heterosetosa , but in the new species the blades are appreciably longer and unidentated. Also it is remarkable the wide muscle cell rows of the proventricle, being much slender in the other species.

None of the examined specimens have all the antennae; the holotype has only the median one and one of the paratypes has only a lateral one, being similar to the median antenna of the holotype in size; so, we assume that the species has three antennae, short, but longer than the dorsal cirri.

Etymology. We dedicate the species to Pablo Martín-Sosa, a researcher at IEO-Canarias who directed the oceanographic campaigns that provided the material studied in this work.

Habitat. In deep bottoms where coarse sand substrates dominate, from 237 to 833 m.

Distribution. Amanay and Banquete Banks, to the south of Fuerteventura and Conception Bank to the north of Lanzarote (Canary Islands).

Figures

FIGURE 2. Exogone martinsosai n. sp. A, anterior end, dorsal view. B, falcigers, most anterior parapodium. C, spinigerlike compound chaeta, anterior parapodium. D, falcigers, anterior parapodium. E, spiniger-like compound chaetae, midbody parapodium.F, falcigers, midbody parapodium.G, spiniger-like compound chaetae, posterior parapodium. H, falcigers, posterior parapodium. I, dorsal simple chaeta, most anterior parapodium. J, dorsal simple chaeta, anterior parapodium. K, dorsal simple chaeta, midbody parapodium. L, dorsal simple chaeta, posterior parapodium. M, ventral simple chaeta. N, acicula, posterior parapodium. Scale. A: 0.05 mm. B–N: 20 µm.