Holothuria platei Ludwig, 1898

Yves, 2003, The holothurian subgenus Mertensiothuria (Aspidochirotida: Holothuriidae) revisited, Journal of Natural History 37, pp. 2487-2519 : 2508-2512

Holothuria platei Ludwig, 1898

(figures 9A–G, 10A–F)

Holothuira platei Ludwig, 1898 , 432, pl. 56, figures 1–14.

Holothuria Platei : Deichmann et al., 1924: 381, text figure 1.

Holothuria (Holothuria) platei: Panning, 1935d: 11 , text figure 118.

Mertensiothuria platei: Deichmann, 1958: 229 , pl. 3, figures 10–12; Codoceo, 1976: 91; Rozbaczylo and Castilla, 1987: 185; Ramirez and Osorio, 2000: 7.

Holothuria (Mertensiothuria) platei: Rowe, 1969: 149 ; Samyn et al., 2001: 104, 107.

Original name. Holothuria platei Ludwig, 1898 .

Name-bearing type. Holotype,? ZMH (according to Deichmann 1958: 300); existence of type undetermined (Rowe, personal communication).

Type locality. Chile (Juan Fernández) .

Current status. Holothuria (Mertensiothuria) platei Ludwig, 1898 .

Material examined. Chile ( Juan Fernández Island , Bahia del Pade, stat. 39), 26 August 1908, coll. Svenska Mag. Exped. 1907–1908, ZM 30/5 (one specimen) ; Chile ( Juan Fernández Island , Massatierra), April 1917, coll K. Bäckstrom, ZM 30/5-29 (one specimen) ; Chile ( Juan Fernández Island ), MNUHB 3932 (two specimens) and MNUHB 3933 (one specimen) .

Description. Medium size to large specimens (100–230 mm long), cylindrical with mouth and anus terminal. Colour in life varying from brown to almost black dorsally and from light brown to pale greyish white ventrally; tentacles dark brown. Colour in alcohol nearly the same but somewhat faded. Tube feet densely crowded ventrally, present in ambulacral and interambulacral areas. They are wide, short with a terminal disc 0.8–1.2 mm across. Dorsally the tube feet are small, much less numerous than ventrally, without terminal disc and scattered without alignment. Mouth surrounded by 20 very large, bushy tentacles; anus surrounded by five groups of three to four papillae. Calcareous ring with radial plates at least twice as long as the interradial ones; interradial plates with a sharp central tooth, radial plates quadrangular with a central notch on the anterior margin (figure 9A). One very long Polian vesicle (one-quarter of body length) and very long tentacle ampullae (one-fifth to one-sixth of body length). One very short stone canal ending in an ovoid madreporic plate. Longitudinal muscles very large (10–11 mm wide), undivided. Right respiratory tree going up to the calcareous ring. Cuvierian tubules present, but not observed in all specimens.

Ossicles: in the body wall, tables and buttons. Tables very few, with only a single broken one observed in one specimen. Dorsal body wall with buttons (figure 9B); early buttons as rods (figure 9B). Ventral body wall with irregular (figure 9C) and regular (figure 9D) buttons. Buttons generally 100–120 m m long with six to seven pairs of holes. Ventral tube feet with perforated plates (figure 10A; from 70× 140 m m up to 125× 190 m m) located close to the end plate, regular (figure 9E) and irregular (figure 9F) buttons, some rod-like with perforated extremities (figure 9G); end plates ± 800 m m across. Dorsal tube feet with a small end plate (± 250 m m across), buttons (figure 10B) and rods (figure 10C); rods longer (up to 210 m m long) than in the ventral tube feet (up to 130 m m long). Few ossicles in the tentacles, in the shaft as well as in the extremities: spiny and knobbed rods, 125–400 m m long (figure 10D, E), sometimes with forked or tree-like extremities (figure 10F). No ossicles observed in the longitudinal muscles.

Diagnosis. Present note.

Ecology. The species lives in the intertidal zone (Codoceo, 1976; Ramirez and Osorio, 2000). It is attached to rocks in the surf zone or concealed under large stones. When it lives in coarse sand bottoms it is covered with various debris (pebbles, pieces of algae, calcareous tube worms, etc.). The bushy tentacles are extended in the water column. However, intestinal content reveals mainly coarse detrital material (Codoceo, 1976). The species reaches high population densities: 20– 25 specimens per m 2 (Ramirez and Osorio, 2000).

Geographical distribution. At present only known from the type locality (Juan Fernández Is.).

Proposed status. Holothuria platei Ludwig, 1898 (provisionally not referred to a known subgenus).

Comments. With its huge bushy tentacles, the very large perforated plates in the tube feet, the large regular buttons with up to six or seven pairs of holes and the absence of ossicles in the longitudinal muscles, Holothuria platei does not fit well within the genus Mertensiothuria . The bushy tentacles are very similar to the ones of Holothuria (Semperothuria) cinerascens (Brandt, 1835) (see Massin, 1996) and to those of several species belonging to the subgenus Selenkothuria (Deichmann, 1938, 1958; Caso, 1954). This is most probably a convergence indicating a suspension feeding role of the tentacles. The ossicles of H. platei are very different from H. cinarescens and from all the known species belonging to the subgenus Selenkothuria . As already noted by Deichmann (1958), H. platei occupies a rather isolated position. Reduced tables and large buttons seem to belong to Mertensiothuria . However, because of the absence of ossicles in the longitudinal muscles, because of the huge size of the perforated plates of the tube feet and because of the size and shape of the tentacle ossicles, the species can no longer be maintained in the subgenus Mertensiothuria . Provisionally, it will not be referred to a known subgenus.