Rhodactis indosinensis Carlgren, 1943

Oh, Ren Min, Neo, Mei Lin, Yap, Nicholas Wei Liang, Jain, Sudhanshi Sanjeev, Tan, Ria, Chen, Chaolun Allen & Huang, Danwei, 2019, Citizen science meets integrated taxonomy to uncover the diversity and distribution of Corallimorpharia in Singapore, Raffles Bulletin of Zoology 67, pp. 306-321 : 313-314

Rhodactis indosinensis Carlgren, 1943

( Fig. 6 )

Material examined. 1 specimen (syntype), NRS4020 x14, Poulo Condore, Vietnam ; 7 specimens (vouchers), 6 specimens, ZRC.CNI.1352 (REL341, REL343, REL376, REL377), Pulau Hantu, Singapore, coll. R. M. Oh, January 2018 – February 2018 ; 5 specimens, ZRC.CNI.1351 (REL346, REL348, REL350), Sisters’ Islands , Singapore, coll. R. M. Oh, January 2018 – February 2018 .

Description. Oral and pedal discs outline oval and wide. Column low, with longitudinal ridges extending the entire column. Column colour from purple to brown. Marginal tentacles well developed. Discal tentacles increasingly branched and closely arranged near the oral disc margin. Discal tentacles may cover the entire disc surface, appearing robust despite possessing thin walls. Mesenterial filaments may spill out through discal tentacles. Marginal and discal tentacles brown, usually similar in colour to oral disc. Tips of tentacles often a lighter shade or different in colour (e.g., green). Central mouth elevated, oval, with simple discal tentacles on the mound. Light radial lines corresponding to the mesenterial insertions are seen, extending from the mouth, to the disc margin. Marginal tentacles connected to these radial lines. Mesenteries complete. Cnidom atrichs, holotrichs, microbasic b -mastigophores, microbasic p -mastigophores (see Carlgren, 1943).

Remarks. Description follows Carlgren (1943). This species has been recorded in Cambodia, Vietnam, and Japan (Fautin, 2009, 2016). In Singapore, it is known as the ‘carpet’ or ‘white-tip’ corallimorpharian, depending on tentacle colour. Specimens are only found along the southern shores, attached to coral rock in both subtidal and intertidal habitats ( Table 2). Morphological identification is incongruent with molecular phylogenetic placement for the specimen REL350, which has well-developed discal tentacles with branched tips but is placed in the Rhodactis inchoata clade.

Figures

Fig. 6. Rhodactis indosinensis. A, REL341 ex situ; B, C, REL346 ex situ; D, REL350 in situ. Scale bar = 1 cm.