Holothuria (Mertensiothuria) leucospilota (Brandt, 1835)

Yves, 2003, The holothurian subgenus Mertensiothuria (Aspidochirotida: Holothuriidae) revisited, Journal of Natural History 37, pp. 2487-2519 : 2502-2505

Holothuria (Mertensiothuria) leucospilota (Brandt, 1835)

(figures 6A–P, 11D, 12G) Holothuria (Mertensiothuria) leucospilota: Massin, 1999: 27 (synonymy and records before

1999); Conand, 1998: 1178, text figure; Liao, 1998: 80; Lane et al., 2000: 489; Samyn,

2000: 15, table 1; Samyn and Vanden Berghe, 2000; Samyn et al., 2001: 104, 107.

Original name. Stichopus (Gymnochirota) leucospilota Brandt, 1835 .

Name-bearing type. Status and whereabouts undetermined (Rowe and Gates, 1995); neotype, NHM 1968.7.3.105–6 (by present designation).

Type locality. Solomon Islands .

Current status. Holothuria (Mertensiothuria) leucospilota (Brandt, 1835) .

Material examined. Solomon Islands, date of collection unknown, depth unknown, coll. H. G. Vevers, NHM 1968.7.3.105–6 (three specimens, including the neotype: 80 mm in length) ; Solomon Islands, date of collection unknown, depth unknown, coll. H. G. Vevers, NHM 1968.7.3.104 (two specimens) ; Kenya ( Kanamai ), July 1997, 2 m depth, coll. Y. Samyn, MRAC 1667 /KKan9701 (one specimen) ; Tanzania (Pemba Island, Mesali ), July 1998, 1– 5 m depth, coll. Y. Samyn, MRAC 1668 /TMes9954-55-56 (three specimens) ; Kenya ( Kiunga Marine Reserve ), April 1999, 1– 3 m depth, coll. Y. Samyn, IRSNB IG28268 /KKiun9932–33 (two specimens) ; Republic of South Africa (Durban, Vetch Peer ), 3 m depth, coll. Y. Samyn, MRAC 1669 /RSAKZN0016 (two specimens) ; Republic of South Africa ( Sodwana Bay ), 8 m depth, coll. Y. Samyn, MRAC 1670 /RSAKZN00131 (one specimen) .

Description. Intermediate to large cylindrical and elongate species, length in alcohol up to 300 mm. Colour in life: very dark brownish red to black (figure 12G); colour in alcohol brownish with the ventral side somewhat lighter. Ventral tube feet large, relatively short, with brown to grey sucking disc, distributed in the ambulacral areas, and scattering into the interambulacral areas. Bivium with soft, brown papillae in the ambulacral areas. Mouth ventral surrounded by 20 large, black tentacles. Anus terminal, unguarded. Calcareous ring stout with very large radial plates more than three times as wide as the pointed interradial plates. Single club-shaped Polian vesicle. Single stone canal. Cuvierian tubules very thin, abundant, readily ejected.

Ossicles: body wall with tables (figure 6A–C, F, G, J) and buttons (figure 6D, E, H, K). Tables (figure 6A–C, F, G, J) numerous; disc 40–70 m m across, perforated by four central holes and 4–12 peripheral holes of similar size; disc round to quadrangular in outline, rim smooth to spiny; pillars long (one to three cross-beams) in small specimens and short (single cross-beam) in longer specimens; spiny crown with a large central opening, crown narrow in small individuals and wider in longer individuals. Buttons (figure 6D, E, H, K) absent in the body wall of the smallest specimen, more numerous with increasing body length, 40–70 m m long, with two to four (occasionally five) pairs of irregular holes; rim of buttons smooth but irregular; generally larger in the dorsal (figure 6D, E) than in the ventral body wall (figure 6H, K). Dorsal tube feet with rods, buttons and tables (figure 6Q–V). Rods from 50 to 190 m m variously perforated; buttons and tables similar to those of the body wall. Ventral tube feet with large plates, buttons and tables (figure 6L–P). Plates 60–120 m m long, buttons and tables similar to those of the body wall. No ossicles in the tentacles. Longitudinal muscles with simple or perforated rods and rings (figure 11D).

Diagnosis. See Cherbonnier, 1988: 112, figure 45; present note.

Ecology. This species often displays a semi-cryptic behaviour, whereby it hides two-thirds of its body under a coral block (see also figure 12G). Sometimes it can be found exposed on coral rubble or coarse sand. It is mainly an eulittoral species, never observed deeper than 8 m.

Geographical distribution. Tropical and subtropical Indo-Pacific Ocean (see also distribution map Massin, 1999: 29).

Proposed status. Holothuria (Mertensiothuria) leucospilota (Brandt, 1835) .

Comments. As the status and whereabouts of the type material of H. (M.) leucospilota was undetermined until now (Rowe and Gates, 1995) we find it opportune to create a neotype in the present note. We believe that such designation is obligatory to define the nominal taxon objectively. Unfortunately attempts to obtain specimens of H. (M.) leucospilota from the original type locality, i.e. Marshall Island (Ualan), were not successful. However, a search through the huge collection of the Natural History Museum, London resulted in several specimens from the Solomon Islands. The largest specimen in NHM 1968.7.3.105–6 is here designated as the neotype. Following article 76.3 of the International Code of Zoological Nomenclature, the Solomon Islands are now considered the type locality of H. (M.) leucospilota .

It has been documented for several species in Holothuria that the size, appearance and prevalence of ossicle types changes with age (Cutress, 1996; Massin, 1999; Massin et al., 2000). Examination of several specimens of H. (M.) leucospilota of different lengths reveals that as the holothurian increases in size: (1) buttons become more abundant (the smallest specimen, 33 mm in length, has no buttons in the body wall) and tables tend to disappear; (2) the rim of the disc of the tables becomes more spiny; (3) the spire of the tables decreases in length; and (4) the crown becomes wider.

Until now, Erwe (1913) and Panning (1931, 1935e, 1944) described pseudobuttons (as ‘unvollkommene Schnallen’ and ‘falsche Schnallen’) from the longitudinal muscles of H. leucospilota . Erwe (1913, figure 13b) also mentioned rods in these muscles. It is remarkable that these important systematic accounts were ignored for so long.