Acaudina spinifera, 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 : 112-115

Acaudina spinifera sp. nov.

Figures 6–9

Material examined. Holotype. USMCRC-Echi 029, Middle Bank, intertidal, on sandbank, hand collected by Teoh V. Y.J., 13th December 2019.

Paratype. USMCRC-Echi 030, Middle Bank, intertidal, on sandbank, hand collected by Teoh V. Y.J., 13th December 2019 .

Description. Specimen length 180–220mm ( Figure 6–7 ). Body stout and cylindrical. Posterior end tapering when relaxed. Mouth and anus terminal; tend to turn upwards when relaxed. Body wall smooth and not translucent. Body color dark pink with dark brown and orange flecks. Tube feet absent. Respiratory tree and anal papillae present. Anal papillae small. Fifteen digitate tentacles; no terminal digits; a pair of lateral digits. Calcareous ring ( Figure 8 ) solid. Radial piece with bifurcated prolongations at posterior; two ridges running longitudinally converging and connecting at median anterior, forming a notch. Interradial piece with no prolongations at posterior.

Ossicles. Dorsal body wall ossicles consist of doughnut-shaped bodies, perforated plates, and sub-spherical bodies. Doughnut-shaped bodies in dorsal body wall ( Figure 9A–B ) spinose with 31–35μm in length; a single median perforation. Perforated plates in dorsal body wall ( Figure 9C ) spinose with 33–35μm in length. Sub-spherical bodies ( Figure 9D ) spinose with 35–38μm in length. Caudal region body wall ossicles consist of perforated plates, sub-spherical bodies, rosette-like plates, and rods. Perforated plates in caudal region body wall ( Figure 9E ) spinose with 30–40μm in length. Sub-spherical bodies in caudal region body wall ( Figure 9F ) spinose with 30–40μm in length. Rosettes in caudal region body wall ( Figure 9G ) 33–38μm in length. Rods in caudal region body wall present in three forms: rosette-like, thick and rounded, and dumbbell-shaped. Rosette-like rods in caudal region body wall ( Figure 9H ) 40μm in length. Thick rounded rods in caudal region body wall ( Figure 9I ) smooth with 20–35μm in length. Dumbbell-shaped rod in caudal region body wall ( Figure 9J ) 43μm in length. Tentacle ossicles consist of rosettes. Rosette in tentacle ( Figure 9K ) 24μm in length.

Etymology. The epithet spinifera (nominative, feminine) is derived from the Latin word spina– meaning “thorn” with –fera meaning “bearing” that refers to the spinose doughnut-shaped ossicle present in the dorsal body wall.

Remarks. The tentacles with only a pair of lateral digits and the absence of the caudal appendage fits with the description of the genus Acaudina as described by Clark (1908) and Clark & Rowe (1971).

A. spinifera sp. nov. can be distinguished from its congeners based on the presence of spinose doughnutshaped bodies in the body wall ( Figure 9A–B ). Acaudina leucoprocta ( Clark, 1938) , Acaudina punctata ( Sluiter, 1887) , and Acaudina molpadioides ( Semper, 1867) all have smooth doughnut-shaped bodies in the body wall instead.

The presence of rosettes and smooth rods differentiates A. spinifera sp. nov. from Acaudina suspecta Cherbonnier & Féral, 1981 which was described by Cherbonnier & Féral (1981) to only have spinose perforated plates and spinose rods. The spinose rods found in the body wall of Acaudina bacilla Cherbonnier & Féral, 1981 were absent in A. spinifera sp. nov.

The species Acaudina demissa ( Sluiter, 1901) was initially described to only have spinose perforated discs. However, Cherbonnier & Féral (1981) remarked that the ossicles described by Sluiter (1901) was not typical for A. demissa . Instead of spinose perforated discs, Cherbonnier & Féral (1981) re-examined the holotype and described the majority of the ossicles were either more irregular, very spinous, and often sub-spherical in shape, or rods that were finely spinose with both ends expanded. Regardless, A. spinifera sp. nov. can still be differentiated from A. demissa based on the rosettes, smooth rounded rods, and spinose doughnut-shaped bodies, all of which were absent in A. demissa .

Semper (1867) remarked that Acaudina pellucida ( Semper, 1867) does not have any ossicles. Acaudina rosettis O’Loughlin & Ong, 2015 was described to have no ossicle in the tentacles, phosphatized ossicles present in the caudal body wall, and having a “semi-translucent gray to opaque white body wall”. Instead, A. spinifera sp. nov. have rosettes in the tentacles, but phosphatized ossicles were absent, and the body wall was dark pink.

Table 1 provides a summary on the differences between A. spinifera sp. nov. and its congeners based on the ossicles. The following is the identification key to the genus Acaudina .

Figures

FIGURE 6. Acaudina spinifera sp. nov., USMCRC-Echi 029; lateral view. A=Anterior; P=Posterior.

FIGURE 7. Acaudina spinifera sp. nov., USMCRC-Echi 030; lateral view. A=Anterior; P=Posterior.

FIGURE 8. Calcareous ring of Acaudina spinifera sp. nov. viewed from the body cavity, USMCRC-Echi 029. R=Radial plate; IR=Interradial plate; A=Anterior; P=Posterior.

FIGURE 9. Ossicles of Acaudina spinifera sp. nov. USMCRC-Echi 029. A–B. Spinose doughnut-shaped bodies from dorsal body wall; C. Spinose perforated plates from dorsal body wall; D. Spinose sub-spherical bodies from dorsal body wall; E. Spinose perforated plates from caudal region body wall; F. Spinose sub-spherical bodies from caudal region body wall; G. Rosettes from caudal region body wall; H. Rosette-like rods from caudal region body wall; I. Thick rounded rods from caudal region body wall; J. Dumbbell-shaped rod from caudal region body wall; K. Rosette in tentacle.