Trypanosyllis mercedesae, Rodríguez & Martín & Fiege, 2019

Rodríguez, Yolanda Lucas, Martín, Guillermo San & Fiege, Dieter, 2019, A new species and nine new records of Syllidae (Annelida) from the Socotra Archipelago (Indian Ocean), Zootaxa 4651 (2), pp. 235-258 : 242-247

Trypanosyllis mercedesae n. sp.

Figures 4–7

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Material examined. Socotra Archipelago , 12º26.049N 52º08.07E, Kal Farun rock outcrop, 9.5-12.5 m, 03.04.2000 .

Holotype (including 3 permanent slides with parapodia) ( SMF 24983) and one paratype (including 1 permanent slide of a parapodium) ( NHCY 005 ).

Diagnosis. Body long, distinctly flattened, with pigmented dorsal cirri, two thin, clearly marked, red-garnet dorsal bands on each anterior segment, up to the proventricular level, relatively short and thick, pigmented dorsal cirri, and almost triangular teeth on the trepan.

Description. Holotype longest and complete specimen, 44 mm long, 1.25 mm wide, 281 chaetigers ( Fig. 4A ); paratype incomplete, without pygidium, 7.8 mm long, 1.28 mm wide, 69 chaetigers. Antennae and tentacular cirri white-yellowish ( Fig. 4A, B ); dorsal cirri pigmented in garnet or red-wine. Body markedly dorso-ventrally flattened, ribbon-like, and tapered posteriorly. Dorsum of each anterior segment with two transverse red-garnet lines ( Fig. 4 A–B,) disappearing progressively some segments after proventricle. Prostomium oval, wider than long, posteriorly bilobed with a conspicuous cleft; two pairs of garnet coloured eyes, in open trapezoidal arrangement; anterior pair larger than posterior one. One pair of palps slightly shorter than prostomium, completely separated, kidney-shaped. Median antenna inserted frontally, near anterior margin of prostomium, with 23–24 articles. Lateral antennae shorter, with 20 articles, emerging slightly behind median antenna. Tentacular segment small, reduced dorsally, with two pairs of tentacular cirri. Dorsal tentacular cirri with 23 articles, ventral ones with 13–15 articles. Dorsal cirri alternating in length; longest cirri slightly longer than body width. First long dorsal cirri about 32–34 articles next ones 27–30 articles; anterior short dorsal cirri about 17–19 articles. Midbody long dorsal cirri with 22–25 articles; midbody short dorsal cirri 11–19. Posterior long dorsal cirri with 23–25 articles; short ones 13–16. Ventral cirri digitiform, shorter than parapodial lobes ( Fig. 5 A–C). Anterior parapodia with about 12–13 compound chaetae, with falcigerous blades, bidentate, short spines along margin ( Fig. 6A ); gradation in length of blades 48 μm long above, 38 μm below. Number and shape of chaetae varying gradually from anterior to posterior parapodia. Midbody parapodia with 6–7 falcigers each, 44 μm above 28 μm below ( Fig. 6C ), bidentate, proximal tooth small, acute ( Fig. 6C ), distal tooth larger and also pointed; interspace between distal and proximal tooth wide; proximal part of the blade with small spines on edge; most dorsal ones somewhat elongated and more similar to those of anterior parapodia, with both teeth similar and short spines along edge. Posterior parapodia with similar falcigers as midbody, six per parapodium, 38 μm above ( Fig. 6E ), 26 μm below. Anterior parapodia with four aciculae each of different sizes, one of them slightly oblique at tip ( Fig. 6B ); from midbody parapodia, three straight acicula per parapodium, one of them distinctly smaller than other ones ( Fig. 6D ); posterior aciculae also straight and slightly pointed ( Fig. 6F ), two per parapodium, one of them smaller. Pharynx brownish, in holotype across approximately 12 segments; proventricle through 16 segments. Pharynx and proventricle of paratype dissected ( Fig. 7B ); pharynx brownish, through 16 segments, slightly contracted, 1.28 mm long, 0.42 mm surrounded on anterior margin by a crown of 8 finger-shaped papillae ( Fig. 7A ); trepan with 9–10 brownish triangular teeth ( Fig. 7C ); proventricle through 13–16 segments ( Fig. 7B ), 2.1 mm long, 0.57 mm wide, with about 29 muscle cell rows. Pygidium in process of regeneration.

Remarks Trypanosyllis mercedesae n. sp. is characterized by having a long body, distinctly flattened, with dorsal cirri pigmented in garnet or red-wine, two slender but clearly marked reddish bands on each anterior segment, up to the proventricular level, relatively short and thick pigmented dorsal cirri, and short almost triangular teeth on trepan. Trypanosyllis richardi is similar and lives in the nearby area of the Red Sea; however, that species has distinctly longer and slender dorsal cirri, which are unpigmented, the two reddish bands on the dorsum of anterior segments are larger, appearing almost as a single, broad band, also present posteriorly to proventricle, and the pharyngeal teeth are longer, not so acute as those of T. mercedesae n. sp.

According to WORMS (2019) and Álvarez-Campos et al. (2017, 2018), the genus Trypanosyllis currently consists of about 40 valid species (excluding the species transferred to Trypanedenta Imajima & Hartman, 1964 ; Trypanoseta Imajima & Hartman, 1964 and Pseudosyllis Grube, 1863 ). Álvarez-Campos et al. (2017, 2018) revised this genus, and described or re-described numerous species. There are many species of Trypanosyllis with a similar colour pattern, formed by two reddish dorsal bands per segment, at least on anterior segments. Most of the species have both bands slender or one slender and the other larger. Only T. luzonensis ( Pillai, 1965) , from Philippines, China and Australia, has a similar pattern of pigmentation than T. mercedesae , n. sp., formed by two large bands per segment, appearing to be a single band. However, T. luzonensis has the two bands more marked (sometimes almost fused to each other) and larger than those of T. mercedesae n. sp. and they continue almost to the posterior part of body, while disappearing after the proventricle in T. mercedesae n. sp., the dorsal cirri are long and lacking pigmentation, being much shorter, thicker and pigmented in T. mercedesae n. sp. The compound chaetae in both species are similar, but relatively shorter and less elongated in T. luzonensis .

Trypanosyllis krohnii , from W Mediterranean, has a similar colour pattern, but it is proportionally wider, with shorter, unpigmented dorsal cirri, and the compound chaetae are more markedly bidentate (see the re-description in Álvarez-Campos et al. 2017).

Habitat. In dead corals at shallow bottoms (9.5 to 12.5 m).

Distribution. Only known in Kal Farun rock outcrop, Socotra Archipelago.

Etymology. Named after Mª de las Mercedes Rodríguez del Olmo, beloved mother of YLR.

Figures

FIGURE 4. Trypanosyllis mercedesae n. sp., Holotype (SMF 24893); A complete specimen, dorsal view; B anterior end, dorsal view.

FIGURE 5. Trypanosyllis mercedesae n. sp., Holotype (SMF 24893) A anterior parapodium; B midbody parapodium; C posterior parapodium; D Trypanosyllis richardi paratype (SMF 24990) midbody parapodium and long cirri; E midbody short cirri.

FIGURE 6. Trypanosyllis mercedesae n. sp., Holotype (SMF 24893) compound chaetae A anterior; C midbody; E posterior; aciculae, B anterior; D midbody; F posterior.

FIGURE 7. Trypanosyllis mercedesae n. sp., Paratype (NHCY 005) A pharynx detail, papillae and teeth; B pharynx and proventicle; C trepan detail.