Trypanosyllis richardi Gravier, 1900

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 : 247-250

Trypanosyllis richardi Gravier, 1900

Figures 5 , 8 and 9

Trypanosyllis richardi Gravier, 1900: 168 , pl. 9, figs. 12–13.

Material examined. Socotra, Shanitan , 600 m off cold store, 12º40.156N 54º02.850E, 8 m, from almost completely dead Acropora cf. valida , 22.03.1999; 1 specimen (broken in two parts) ( SMF 24985) . Farun rock outcrop, 12º26.049N 52º08.07E, 9.5–12.5 m, 03.04.2000, 3 specimens ( SMF 24986) . Ras Qataninh Bay , dredge, 12º21.789N 53º31.399E to 12º21.780N 53º31.390E, 18-20 m, 09.04.2000, 1 specimen ( SMF 24987) . Hawlaf , off the jetty, 12º41.062N 54º04.508E, Galaxea sp. colonies on sand, 12–14 m, 19.03.1999, 1 specimen ( NHCY 006 ) . Off Hawlaf dune, 12º40.519N 54º04.170E, from dead Acropora cf. valida , 4-5 m, 21.03.1999, 1 specimen ( SMF 24989) . Off Quadub , fishery village, in front of airport, 12º38.945N 53º56.028E, from dead Galaxea sp., 6-8 m, 18.03.1999, 1 specimen (including 5 permanent slides of parapodia) ( SMF 24990) .

Comparative material examined: Type material of Trypanosyllis richardi Gravier, 1900 was loaned from the Museum National d’Histoire Naturelle, Paris ( MNHN- IA-TYPE 1400).

Description. Longest and complete specimen from Socotra ( SMF 24990) 36.4 mm long (including a female stolon in formation), 2 mm wide, 207 chaetigers; remaining specimens all incomplete; one specimen ( SMF 24985) about 22 mm long, 1 mm wide; three specimens ( SMF 24986) about 21.42, 8.86, 18.57 mm long, and 1.78, 1.27, 1.57 mm wide respectively; longest incomplete specimen ( SMF 24987) 40.7 mm long, 1.7 mm wide with 140 chaetigers; one specimen ( NHCY 006) about 7.2 mm long, 1 mm wide; one specimen ( SMF 24989) 18.5 mm long, 1.4 mm wide. Holotype ( SMF 24990) incomplete, 42 mm long, 2 mm wide, 170-175 chaetigers, antennae and tentacular cirri white or showing only light brownish coloration, dorsal cirri unpigmented ( Fig. 8A ). Body strongly dorso-ventrally flattened, ribbon-like, tapered posteriorly. Dorsum of each anterior segment with two transverse brownish lines, very close to each other, leaving only a thin unpigmented area in-between reaching posterior segments of proventricle, progressively less pigmented, reaching to most posterior segments. Prostomium oval, almost wider than long; posteriorly bilobed, each part showing a dark oblique mark, with a conspicuous cleft on posterior margin; two pairs of brown eyes in open trapezoidal arrangement; anterior pair larger than posterior. One pair of pear-shaped palps, similar in length to prostomium, completely separated. Median antenna inserted frontally, near anterior margin of prostomium, with 28 articles. Lateral antennae shorter, with 15 articles, emerging slightly posterior to median antenna. Tentacular segment small, reduced dorsally, with two pairs of tentacular cirri. Dorsal tentacular cirri with 63 articles, ventral ones with 14–15 articles. Dorsal cirri alternating in length ( Fig. 5 D–E); longer cirri slightly longer than body width. First long dorsal cirri about 71 articles, next ones 51–71 articles; anterior short dorsal cirri about 19–33 articles. Midbody long dorsal cirri 22–25 articles; midbody short dorsal cirri 10–15. Posterior long dorsal cirri 40 articles; short ones 17–18. Ventral cirri digitiform, longer than parapodial lobes ( Fig. 5D ). Anterior parapodia with about 12–13 compound chaetae, strongly heterogomph, shafts distally spinose, with falcigerous blades, bidentate, both teeth similar, short spines along margin ( Fig. 9A ); gradation in length of blades 67 μm long above, 39 μm below. Number of chaetae per parapodium, and shape, varying gradually from anterior to posterior parapodia. Midbody parapodia each with 9–11 falcigers, similar to anterior ones but shorter, 54 μm above 38 μm below ( Fig. 9C ); most dorsal chaetae similar to anterior ones, remaining chaetae, bidentate, proximal tooth small, acute ( Fig. 9C ), distal tooth bigger and also pointed; interspace between distal and proximal tooth wide; blade with short spines on edge. Posterior parapodia with similar falcigers than midbody but slightly shorter, 8–9 in each parapodium 38 μm above ( Fig. 9E ), 30 μm below. Anterior parapodia each with 4 straight aciculae of differ- ent sizes ( Fig. 9B ); from midbody parapodia, 4 straight acicula per parapodium, one of them distinctly smaller than the others ( Fig. 9D ); posterior parapodia with 2 similar aciculae, pointed ( Fig. 9F ), one of them smaller. Pharynx and proventricle dissected ( Fig. 8B ). Pharynx brownish, through 15 segments, slightly contracted, 2 mm long, 0.64 mm wide, surrounded anteriorly by a crown of 23–25 digitiform papillae ( Fig. 8 B–C). Trepan with 7–8 brownish triangular teeth ( Fig. 8 B–C). Proventricle through 16 segments, 2.64 mm long, 0.88 wide with about 31–33 muscle cell rows.

Remarks. Knox (1960) synonymized Trypanosyllis richardi with T. taeniaeformis ( Haswell, 1886) , which was previously synonymized with T. zebra by Haswell (1920), including T. richardi in the same synonymy. Trypanosyllis taeniaeformis has a different colour pattern, although similar, with several slender transversal brown rows and other narrow bands of the same colour between the joints of the dorsal cirri ( Haswell, 1886). Probably these two species are different but it is difficult to prove because the type species of T. taeniaeformis was lost (Australian Museum, pers. com.). In the present paper, we consider that T. richardi is a valid species, based on the study of the type specimen, and the new material from Socotra that indeed is geographically close to Djibouti, the type-locality of T. richardi . Trypanosyllis leivai Álvarez-Campos, Riesgo & San Martín, 2017 , from the Philippines, has proportionally more slender body, with similar colour pattern, but slightly different, having two reddish transversal bands per segment, one longer and slender, and the other shorter and wider (see Álvarez-Campos et al. 2017). Trypanosyllis californiensis Álvarez-Campos & Rouse, 2017 , from California, also has long dorsal cirri, but the body is markedly more slender than T. richardi , and the two bands per segment are much thinner (see Álvarez-Campos et al. 2017). Trypanosyllis cristoboi Álvarez-Campos, Taboada, San Martín, Leiva & Riesgo, 2018 , from the Philippines, also has long dorsal cirri, but the body is also slender, there is a single, broad, pigmented band per parapodium on dorsum, and the chaetae have distinctly longer and slender articles (see Álvarez-Campos et al. 2018).

Compound chaetae of all these species are very similar, although having small differences. Only molecular data and differences in details of body and pigmentation pattern allow to distinguish these similar species (see Álvarez- Campos et al., 2017, 2018).

Habitat. On Socotra Island on corals and algae on hard substrate.

Distribution. Djibouti. New record for Socotra.

Figures

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 8. Trypanosyllis richardi Paratype (SMF 24986); A anterior end, dorsal view; B pharynx and proventricle; C pharynx papillae and trepan detail. Odontosyllis polycera (SMF 24991); D pharynx and proventricle.

FIGURE 9. Trypanosyllis richardi Paratype (SMF 24990); compound chaetae; A anterior; C midbody; E posterior; aciculae, B anterior; D midbody; F posterior.