Holothuria (Cystipus) yann Samyn

Samyn, Yves & Vandenspiegel, Didier, 2016, Sublittoral and bathyal sea cucumbers (Echinodermata: Holothuroidea) from the Northern Mozambique Channel with description of six new species, Zootaxa 4196 (4), pp. 451-497 : 458

Holothuria (Cystipus) yann Samyn sp. nov.

( Fig. 2 A – H)

Material examined. Type material: IE2007-764 (holotype & 2 paratypes, collected in front of Mahajamba Bay )

Comparative type material. EcHh 3550 (holotype of Holothuria (Cystipus) mammosa Cherbonnier, 1988 ; Nossi-Bé, Ambaro Bay, Madagascar, coll. Crosnier, 4.XII. 1964, 24 m depth).

Type locality. Madagascar, in front of Mahajamba Bay , Station CP 3282 (Decimal coordinates: -14.87; 46.97).

Etymology. This species is named after Yann Samyn , twin-daughter of Reen Tallon and Yves Samyn, in recognition of her patience when her dad is writing up some taxonomic work at home. The species epithet has been put in apposition.

Known geographical distribution. For now only known from the type locality.

Taxonomic description (holotype and paratypes). External anatomy — Holotype 110 mm long and 20 – 50 mm wide, with maximum circumference of 120 mm. First paratype 100 mm long and 15 – 40 mm wide, with maximun circumference of 115 mm. Second paratype 112 mm long and 20 – 30 mm wide with maximum circumference of 85 mm (fig. 2A,B). Body tapering towards both ends, but especially posteriorly. Body wall heavily wrinkled, both dorsally and ventrally. Very gritty to the touch. Bivium convex, high. Trivium flat. Bivium separated from trivium by regular row of small lateral papillae. Mouth ventral, surrounded by collar of small papillae which are very reduced ventrally. Number of tentacles in holotype and paratypes could not be counted due to contraction. Anus subdorsal, narrow, not surrounded by papillae. Color in alcohol: bivium beige, marked with parallel irregular brown lines that become thicker mid-dorsally; trivium beige, also marked with irregular brown lines. Ventral tube feet very scarce, only some in ambulacral areas, posteriorly in two uneven rows. Dorsal podia slightly more numerous and spread over complete surface. Podia and lateral papillae white.

Internal anatomy (paratypes, holotype not dissected)—Calcareous ring with interradial pieces nearly as wide and slightly less long than radial ones; radial pieces with anterior notch, interradial ones slightly convex posteriorly. Stone canal not observed, Polian vesicle single, 20 – 25 mm long. Tentacle ampullae small; 8 – 10 mm long, 12 counted. Gonad not observed. Gut filled with fine muddy sediment. Right respiratory tree well developed reaching oral end of body; left respiratory tree poorly developed going up to mid body. Longitudinal muscles, bifid and flat, 6 mm wide, edges attached. Cuvierian tubules present, extremely thick and positioned in a contracted ball like structure

Ossicles —Tentacles with spinose rods up to 250 µm long (fig. 2C), ventral and dorsal body wall with similar tables and buttons (fig. 2D,E). Tables numerous, rim of disc undulating to spiny, disc knobbed at edge, up to 100 µm across, perforated by four central and up to 16 small peripheral holes, pillars short (30 – 45µm high), with 0 – 1 cross beams, smooth and ending in a spiny crown. Buttons very numerous, nodulous centrally and at rim, 40 to 110 µm long, generally 3 to 4 pairs of holes, but with up to 7 pairs of holes in those from ventral body wall; holes relatively small and often obscured by numerous knobs; few buttons modified into fenestrated ellipsoids (fig 2D,E). Dorsal tube feet, ventral tube feet and lateral papillae with elongated plates up to 180 µm in addition to tables and buttons that are similar to those of body wall (figs 2F – H). Longitudinal and suspensor muscles of cloaca, cloaca, gonad and respiratory trees devoid of ossicles.

Remarks. The ossicle assemblage, with tables with heavily knobbed disc and low spire and with buttons which are irregularly knobbed and which have narrow, sometimes nearly obliterated holes, places this species in the Holothuria subgenus Cystipus Haacke, 1880 . In Cystipus twelve species are currently recognized (Laguerda- Figueras & Solis-Marin 2009). H. (C.) yann can easily be distinguished from the other species in Cystipus by its coloration pattern. Its ossicles resemble those of H. (C.) mammosa Cherbonnier, 1988 , ( Fig. 2 ) but H. yann can easily be differentiated from H. mammosa because the cloaca of the latter holds perforated rods (new observation by authors) whereas H. yann has no ossicles in the cloaca. Moreover, H. mammosa is characterized by having large conical papillae over the complete body wall whereas H. yann only has reduced lateral papillae. H. mammosa , known only from the holotype, was collected at 24 m depth, whereas the three known specimens of H. yann were collected at 261 m depth, making it the deepest Cystipus species ever collected.

Figures

FIGURE 2. Holothuria (Cystipus) yann sp. nov. A – B. Dorsal view (A) and ventral view (B) of paratypes. C – G: SEM photos of ossicles from tentacles (C), dorsal (D) and ventral (E) body wall, dorsal tube feet (F), lateral papillae (G) and ventral tube feet. A, B = 1 cm; C = 50 µm; D – H = 20 µm.