Euthyonidiella zulfigaris, Teoh & Woo, 2022

Teoh, Vincent Yong Jian & Woo, Sau Pinn, 2022, Two new species of sea cucumbers (Echinodermata: Holothuroidea) from the seagrass meadow of Penang, Malaysia, Zootaxa 5128 (1), pp. 107-118 : 108-112

Euthyonidiella zulfigaris sp. nov.

Figures 2–5

Material examined. Holotype. USMCRC-Echi 010, Middle Bank, intertidal, buried under mud, hand collected by Teoh V. Y.J., 10th February 2020.

Paratype. USMCRC-Echi 009, USMCRC-Echi 011, Middle Bank, intertidal, buried under mud, hand collected by Teoh V. Y.J., 10th February 2020 . USMCRC-Echi 026, Middle Bank, intertidal, buried under mud, hand collected by Teoh V. Y.J., 13 th December 2019 .

Description. Diameter 80–110mm ( Figure 2–3 ). Mouth and anus on dorsal plane. Body expands into a sphere when disturbed. Tube feet scattered densely all over the body; denser ventrally; darker in color near the base. Body color mixture of gray and white. Body wall thin and slightly translucent when expanded. Twenty dendritic tentacles; 15 larger tentacles and five smaller tentacles. Calcareous ring ( Figure 4 ) short and strong. Anterior of radial plate split into three notches; one deep notch down the middle and two shallow notches situated on the left and right. Posterior of radial plate split into two short tapering projections; posterior projections solid and not composed of smaller pieces. Interradial plates tapering sharply at anterior. Two short projections at posterior of interradial plates.

Ossicles. Dorsal body wall ossicle consists of tables in two forms. First form of table ( Figure 5A–B ) 48–62μm in diameter, spire low with 3–4 pillars; crown with 3–4 spines. Disc of first form table smooth and rounded, surface with numerous irregular perforation. Second form of table ( Figure 5I ) 88μm in diameter, spire low with four pillars; crown with four spines. Disc of second form table round; disc surface smooth with eight peripheral perforations; disc margin denticulate. Ossicles in anal region consist of tables ( Figure 5H ) measuring 74–78μm in diameter with low spire and four pillars. Disc surface smooth with eight peripheral perforations and one central perforation; disc margin denticulate. Crown of table in anal region rounded with few spines. Tube feet ossicles consist of the endplate. Endplate in tube feet ( Figure 5C ) 417μm in diameter with multiple perforations. Tentacle ossicles consist of large rods, spinose rods, small rods, and rosettes. Large rods in tentacle ( Figure 5D ) 250–367μm in length; perforated on both ends. Spinose rod in tentacle ( Figure 5F ) 242μm in length. Small rod in tentacle ( Figure 5E ) smooth with 107μm in length. Rosettes in tentacle ( Figure 5G ) 75–155μm in length.

Etymology. Species named after Prof. Zulfigar Yasin who has greatly contributed to the biodiversity study in Malaysia and one of the pioneer scientists to study Pulau Gazumbo and Middle Bank.

Remarks. The number of tentacles (20 tentacles) and the solid posterior prolongations of the calcareous ring of the holotype and paratypes of E. zulfigaris sp. nov. best fits with the description of the genus Euthyonidiella by Heding & Panning (1954). Currently the genus Euthyonidiella have 12 valid species. This species can be differentiated from its congeners based on the table ossicles with round disc and spire formed with four pillars, absence of support tables in the tube feet, and the morphology of the calcareous ring.

The table ossicles with spires formed with four pillars is an important morphology feature that can be used to distinguish the species E. zulfigaris sp. nov. from most of its congeners that have table ossicles with spires formed with two pillars only. Euthyonidiella ambigua ( Heding, 1942) , Euthyonidiella destichada ( Deichmann, 1930) , Euthyonidiella huwi O’Loughlin in O’Loughlin et al., 2014, Euthyonidiella kyushuensis Heding & Panning, 1954 , Euthyonidiella occidentalis ( Ludwig, 1875) , Euthyonidiella trita ( Sluiter, 1910) , and Euthyonidiella zacae ( Deichmann, 1938) all have table ossicles with spires formed with two pillars only.

The remaining congeners having table ossicles with spires formed with four pillars can be differentiated from E. zulfigaris sp. nov by the disc shape of the table ossicles and the presence of support tables in the tube feet. Comparison of the disc shape of the table ossicles of the species E. zulfigaris sp. nov. and Euthyonidiella arenicola ( Pawson & Miller, 1992) revealed that they were distinct: the disc shape of E. zu lfigaris sp. nov. was circular while E. arenicola has a square or rectangular shaped disc. Subsequently, E. zulfigaris sp. nov. can be distinguished from Euthyonidiella aculeata ( Ludwig, 1894) , Euthyonidiella dubia Cherbonnier, 1958 , and Euthyonidiella tungshanensis ( Yang, 1937) based on the absence of support modified table ossicles which consist of a spire found in the tube feet. The species E. zulfigaris sp. nov. lacks the support modified table ossicles in the tube feet which was present in E. aculeata , E. dubia , and E. tungshanensis .

The following is the identification key to the genus Euthyonidiella .

Figures

FIGURE 2. Euthyonidiella zulfigaris sp. nov. USMCRC-Echi 010; dorsal view. A=Anterior; P=Posterior.

FIGURE 3. Euthyonidiella zulfigaris sp. nov. USMCRC-Echi 010; ventral view. A=Anterior; P=Posterior.

FIGURE 4. Calcareous ring of Euthyonidiella zulfigaris sp. nov. viewed from body cavity. USMCRC-Echi 010. R=Radial plate; IR=Interradial plate; A=Anterior; P=Posterior.

FIGURE 5. Ossicles of Euthyonidiella zulfigaris sp. nov. USMCRC-Echi 010. A. Tables in dorsal body wall; B. Tables with three-pillared spires in dorsal body wall; C. Endplate in tube feet; D. Large rods in tentacle; E. Small rod in tentacle; F. Spinose rod in tentacle; G. Rosettes in tentacle; H. Tables in body wall near anus; I. Table in dorsal body wall.