Actinocucumis Ludwig, 1875

P. Mark O’Loughlin, Melanie Mackenzie & Didier Vandenspiegel, 2014, New dendrochirotid sea cucumbers from northern Australia (Echinodermata: Holothuroidea: Dendrochirotida), Memoirs of Museum Victoria 72, pp. 5-23 : 17-19

Actinocucumis Ludwig, 1875

Actinocucumis Ludwig, 1875: 91 .— Théel, 1886: 125.— H. L. Clark, 1946: 402–403.— Heding and Panning, 1954: 70–72.— A. M. Clark and Rowe, 1971: 204.

Type species. Actinocucumis typica Ludwig, 1875 (type locality Queensland, Bowen, 20°S 148°E)

Other species and type localities. Actinocucumis chinensis Liao and Pawson, 2001 (off Hainan, South China Sea ) ; A. cornus ( Heding, 1934) (Hong Kong); A. difficilis Bell, 1884 (Torres Strait, north-east Australia); A. longipedes Clark, 1938 (Broome, north-west Australia); A. simplex ( Sluiter, 1914) (Indonesia) ; A. solanderi O’Loughlin sp. nov. (off King George River , northern Australia) (see below).

Remarks. Heding and Panning (1954) listed numerous synonymies for Actinocucumis typica , with lengthy discussion. We have not examined the relevant type specimens but based on the figures and descriptions in the literature, and on our sensu stricto diagnosis of A. typica below, we raise all of these species out of synonymy.

We note that in discussing their synonymies Heding and Panning (1954) observed in their slide preparations from Actinocucumis typica and Actinocucumis cornus specimens small elongate plates with two long mid-plate perforations and two small distal ones. This form of ossicle was illustrated by H. L. Clark (1938) for Actinocucumis longipedes . Ludwig (1875) did not illustrate this form of ossicle and we have never observed such ossicles in our preparations from specimens of A. typica from the region of the type locality and across northern Australia. It appears to us that Heding and Panning were not examining specimens of A. typica .

Two ossicles are drawn for Actinocucumis typica in Clark and Rowe (1971 ; fig. 95 e and e’). We have seen only the left hand side form (e) in the specimens of A. typica that we have examined, and this is the only form in the original description by Ludwig (1875). The right hand side form (e’) appears to be typical of Actinocucumis longipedes and was referred to by Heding and Panning (1954) above. The two ossicle forms appear to have been drawn from a specimen of A. longipedes .

We note that the Clark and Rowe (1971) illustration of ossicles from A. typica (pl. 30 fig. 4) is in fact from a type specimen of Actinocucumis difficilis Bell that was judged to be a con-specific with A. typica . The ossicles appear to us to exemplify A. typica , and that adds weight to the probability of a synonymy (NHMUK type information confirmed by Andrew Cabrinovic). There are no small elongate plates with two long mid-plate perforations and two small distal ones in this preparation.

The single type specimen from Hong Kong of Phyllophorus cornus Heding, 1934 has tube feet all over the body, five inner tentacles and 15 outer, and five anal teeth. Ossicles from the type of Actinocucumis cornus were used for the illustration in Heding and Panning (1954, fig. 19) of the ossicles of A. typica . The original illustration of ossicles for A. cornus ( Heding 1934) did not show fenestrated ellipsoids. That in Heding and Panning (1954) did show fenestrated ellipsoids. Neither illustrated the small plates with two long and two small distal perforations that Heding and Panning (1954) indicated were present. We judge that the status of A. cornus as conspecific with A. typica remains uncertain, and we raise it out of synonymy as an Actinocucumis species.

Pseudocucumis quinqangularis Sluiter, 1901 from Indonesia has posterior prolongations on the radial plates of a composite calcareous ring, 12 large outer and six small inner tentacles, and an absence of figure-8 ossicles and fenestrated ellipsoids. It is not a species of Actinocucumis and we raise the species out of synonymy in the original combination to await further study.

The single small type specimen from Ceylon of Actinocucumis donnani Pearson, 1903 does not have the tentacles present, has a composite calcareous ring with long posterior prolongations on the radial plates, and has body wall ossicles that are not fenestrated ellipsoids or any form of table. It is not an Actinocucumis species. In the absence of tentacles it is not possible to re-assign the species that we regard as incertae sedis.

The illustrations for Phyllophorus simplex Sluiter, 1914 indicate ossicles that do not include fenestrate ellipsoids and typical figure-8 plates, and the description reports tube feet covering the body. It is not conspecific with Actinocucumis typica , and we raise it out of synonymy with reservations as an Actinocucumis species.

H. L. Clark (1938, 1946) examined numerous specimens of Actinocucumis from northern Australia and was convinced of the existence of four species: A. typica , A. difficilis , A. longipedes , A. quinuangularis. We reject A. quinuangularis as an Actinocucumis species (above), but accept the judgment by Clark who recognized the other three species. We raise A. difficilis and A. longipedes out of synonymy here. In the case of A. difficilis we defer to the experience of H. L. Clark (1938, 1946) who had an abundance of material to examine, but we also judge that the morphological characters that he used to distinguish this species are probably variable characters. We think that a confirmed synonymy requires more consideration. The presence in A. longipedes of small elongate plates with two long mid-plate perforations and two small distal ones is apparently systematically distinctive.

We note the absence of fenestrated ellipsoids and radial papillae in Actinocucumis chinensis and continue to refer this species to Actinocucumis with reservation, as did Liao and Pawson (2001).