Stichopus fusiformiossa Woo

Woo, Sau Pinn, Yasin, Zulfigar, Tan, Shau Hwai, Kajihara, Hiroshi & Fujita, Toshihiko, 2015, Sea cucumbers of the genus Stichopus Brandt, 1835 (Holothuroidea, Stichopodidae) in Straits of Malacca with description of a new species, ZooKeys 545, pp. 1-26 : 9-15

Taxon classification Animalia Aspidochirotida Stichopodidae

Stichopus fusiformiossa Woo sp. n. Figs 10, 11, 12, 13, 14

Material examined.

Three specimens: Holotype, USM/MSL/PSS001, collected from Pulau Songsong (5°48'31.2"N, 100°17'38.0"E), Kedah, Malaysia, 6m depth, on sand, fixed in 99% ethanol. Paratype 1, USM/MSL/PSS002, collected from Pulau Songsong (5°48'31.2"N, 100°17'38.0"E), Kedah, Malaysia, 8m depth, on sand, fixed in 99% ethanol. Paratype 2, USM/MSL/PP003, collected from Pulau Songsong (5°48'31.2"N, 100°17'38.0"E), Kedah, Malaysia, 7m depth, on sand, fixed in 99% ethanol.

Type locality.

Straits of Malacca, Malaysia: Pulau Songsong, Kedah, 05°48'31.2"N, 100°17'38.0"E, on sandy substrate adjacent to a reef area, at a depth of 6-8 m, collected by Woo SP and Zulfigar Y.

Description.

External morphology: Body quadrangular in cross-section with slight rounded four sides. Body wall firm, rugose, and wrinkled surface; variously-sized tiny warts regularly-arranged on dorsal body (Fig. 10). Dorsal body brown in background colour, with patchy beige areas and black patches; latter usually running from anterior to posterior ends and concentrated in middle part of body, and absent in some specimens. Ventral body wall light beige background with two orange, narrow lines spreading from oral to aboral. Large dorsal papillae 0.5-1.0 cm in width at base in the holotype, but highly variable between specimens, more or less arranged in two continuous rows; smaller dorsal papillae scattered on dorsal body; colour of dorsal papillae black, with apex always white. Two rows of large (about 2 cm), white-coloured papillae aligned and arranged in straight line along ventro-lateral edges. Minute pa pillae forming ring surrounding oral opening. Tube feet in ambulacral areas, more numerous in central ambulacral areas than in lateral ones. Two interambulacral areas very narrow, with lesser number of tube feet. Tube feet fairly long, 3-5 mm in length. All specimens examined having 20 peltate-shaped tentacles. Anus terminal.

Spicules: Spicules in dorsal body consisting tables and rosettes (Fig. 11 A–D). Many tables in dorsal body having large base with four central perforations and mul tiple peripheral perforations; four pillars erected from base forming a spire connected by a cross beam, with spines at the tip (Fig. 11A). Some tables in dorsal body having smaller base with less peripheral perforations; pillars connected incompletely with a crossbeam, tip of spire without crown of spines (Fig. 11D). Tables in dorsal body sometimes with pillars reduced to knobs and disc with four central perforations and limited peripheral perforations (Fig. 11B). Papillae consisting large tables, reduced tables, rosettes, C-shape rods, X-shaped rods, and rods (Fig. 13 A–I). Large tables in papillae with multiperforated base disc; four pillars forming spire connected with a crossbeam, tip of pillar very spiny (Fig. 13A). Reduced tables in papillae larger compared to reduced tables in dorsal body (Fig. 13B). Rosettes in papillae form simple curving to extensive bifurcations at both ends (Fig. 13D); smaller rosettes more complex in bifurcations (Fig. 13G). C-shaped rods in papillae simple, some modified to S-shaped rods (Fig. 13E). X-shaped rods in papillae have bifurcate endings in each arms; some with five arms (Fig. 13H). Rods in papillae with rough surface (Fig. 13I). Spicules in tube feet mainly large rods with perforated central plate, multiperforated plates, and tables (Fig. 12 E–G). Surface of rods in tube feet rough, covered with spinelets; numbers and sizes of perforations on central plates of tube feet vary between rods. Tables in tube feet simpler compared to tables in dorsal body and papillae; tip of pillars less spinous and forming small crowns. Spicules in the tentacles consisting of fusiform spicules and rods (Fig. 11A, B). Fusiform spicules spindle-like in shape with dense spines interconnected to each other forming some hollow spaces in between (Fig. 14B). Rods in tentacles rough, slightly curved, and densely covered with spinelets at both ends.

Remarks.

This new species looks very much like Stichopus horrens in its body colouration. They both have similar, grey-brown background with irregular grey and black spots in colour. The live specimens of this species do not have very long papillae as observed in Stichopus horrens reported by Rowe and Gates (1995) and Massin et al. (2002). Stichopus fusiformiossa also lacks tack-like table spicules in the papillae which are the definitive taxonomic feature for Stichopus horrens . The prominent white and black colour of the papillae is distinctive to separate Stichopus fusiformiossa from Stichopus rubermaculosus with the red-coloured papillae, Stichopus quadrifasciatus that has brown to red papillae tip, and from Stichopus chloronotus with yellow-coloured papillae. Furthermore, Stichopus quadrifasciatus has four transverse black-grey bands on the dorsal body wall, which are not seen in Stichopus fusiformiossa . The sporadic arrangement of papillae on the dorsal body of Stichopus fusiformiossa do not have consistent nor specific patterns as similarly observed in Stichopus horrens in this study. However, the two rows of large, black papillae with white tip, arranged in a straight line along ventro-lateral edges are not seen in any other species.

Stichopus fusiformiossa lacks C-shaped rods in the dorsal body, which is commonly seen in the other Stichopus species. Reduced tables are found in the dorsal body in Stichopus fusiformiossa and Stichopus herrmanni , but the former lacks rosettes and C-shaped spicules that are present in the dorsal body of Stichopus herrmanni . The C-shaped rods in the papillae of Stichopus fusiformiossa are strongly modified and do not resemble to any spicules observed in the other Stichopus species except the C-shaped rods of Stichopus chloronotus ( Theel 1886; Sluiter 1887; Ludwig 1887; Mitsukuri 1912). But the colouration and arrangement of papillae easily separate Stichopus fusiformiossa from Stichopus chloronotus .

The X-shaped rods in the papillae of Stichopus fusiformiossa have been only found in Stichopus variegatus (now Stichopus herrmanni ) by Cherbonnier (1988). The X-shaped rods of Stichopus variegatus (now Stichopus herrmanni ) are derived from rosettes ( Cherbonnier 1988). Careful examination of his drawings ( Cherbonnier 1988: fig. 62H) suggested that X-shaped rods of Stichopus fusiformiossa were more rigid and angled compared to the curvy and slender ones of Stichopus variegatus (now Stichopus herrmanni ).

The thick rods with rough surfaces seen in Stichopus fusiformiossa are commonly found in the tentacles of any other species of Stichopus . Fusiform and spindle-liked spicules instead are rare and only shared with Stichopus variegatus (now Stichopus herrmanni ) ( Cherbonnier 1947, fig. C). Since Stichopus variegatus had been separated to either Stichopus herrmanni and Stichopus monotuberculatus by Rowe and Gates (1995), the presence of fusiform and spindle-like spicules can be accorded to Stichopus fusiformiossa as a character differentiating it from both Stichopus herrmanni and Stichopus monotuberculatus because both Stichopus herrmanni and Stichopus monotuberculatus lack the presence of this spicule. A reexamination of specimens of Cherbonnier (1947) collected from the Gulf of Oman, Madagascar, and the Red Sea are necessary to establish the correct species name of those specimens.

Etymology.

The new specific name is a compound descriptive name from the combination of adjective-noun derived from the Latin words of fusiform (fusiformis) and bone (ossa). The name is nominative, neuter, and plural; referring to the distinctive fusiform and spindle-liked spicules found in the tentacles.