Sclerothyone nozawai ( Mitsukuri, 1912 ) Thandar, 2021

Thandar, Ahmed S., 2021, Nomenclatural changes in some sea cucumbers with the erection of a new genus and description of a Thyone? juvenile (? n. sp.) from the Gulf of California (Echinodermata: Holothuroidea: Dendrochirotida), Zootaxa 5026 (4), pp. 507-526 : 509-511

Sclerothyone nozawai ( Mitsukuri, 1912) n. comb.

Figures 1–3

Cucumaria nozawai Mitsukuri, 1912 ; 249, text fig 50.

Havelockia nozawai Panning, 1949 ; 466 (passim, transferred to Thyone in addendum but accepted in Havelockia by WoRMS (529494, accessed 16 June 2021).

Material examined. USNM E2285 , North Pacific Ocean, Japan, Hokkaido, Hakodate Bay , 41° 45’ N 140° 40’ E, USFC, Albatross R /V, 19 IX 1896, 21 m, det. W.K Fisher as Havelockia nozawai , 2 spec.

Distribution. Japan, shallow.

Remarks. This species was originally based on a single specimen and judging from available literature has not been recorded since. Despite the singularity of the specimen the type is well described and illustrated by Mitsukuri (1912). The two current specimens in the Smithsonian collection are clearly referable to this species but both have been previously dissected, the larger one (35 mm) lacks the calcareous ring whereas, in the smaller specimen (30 mm), the ring is intact and quite conspicuous, displaying the characteristic features of the calcareous ring of the type species of the genus. The tube feet are distinctly serially arranged in two distinct rows per ambulacrum with naked interambulacra, a feature not characteristic of Havelockia which has scattered podia. The body wall ossicles comprise tables ( Figure 2 & 3A ) with an elongated disc perforated by many holes and an ill-formed 2-pillared spire as well as multilocular spire-less plates which obviously are reduced tables. The introvert deposits ( Figure 1B & 3C ex holotype) comprise only well-formed tables with an irregular smooth disc perforated by six or more holes (up to 16), a well-formed spire of moderate height with a single cross-bar, terminating in few short teeth. The tentacle deposits are of two types: tables with an elongated, sometimes spinose, curved disc with four central perforations and several at each end and a short spire ending in several teeth ( Figure 1A ), as well as minute, thin-walled, usually multilocular plates with or without a serrated margin ( Figure 1C ). The tube feet ossicles comprise tables with a slightly curved disc and a short, multi-dentate spire (as in holotype - Figure 3A ). The tube feet end plates are remarkably reduced or mostly absent.

The ambulacral restriction of the tube feet, the form of the calcareous ring and body wall ossicles strongly suggest that the species can neither be ascribed to Thyone nor to Havelockia .

It is therefore now transferred to the genus Sclerothyone in the family Sclerothyonidae . Arumugam (2011), in a yet unpublished work and on my advice, transferred the species to Temparena . Now having looked at the ossicles of the holotype of C. nozawai , this view cannot be upheld as there are no distinct plates in the body wall but just reduced tables resembling plates, although the calcareous ring does resemble that of the type species of Temparena . Sclerothyone nozawai n. comb. differs from the type species of Sclerothyone in possessing distinct tables in the tube feet, tentacles and introvert, whereas the type species ( S. velligera ) possesses only plates in the introvert and tentacles and some sort of reduced tables in the tube feet. The ossicles of the USNM specimen are illustrated in Figures 1 & 2 and those of the holotype in Figure 3 .

Figures

FIGURE 1. Sclerothyone nozawai (Mitsikuri, 1912) n. comb. USNM E2285. A. Tables from tentacles; B. Introvert tables; C. Tentacle plates. (All to same scale).

FIGURE 2. Sclerothyone nozawai (Mitsikuri, 1912) n. comb. USNM E2285, SEM of body wall ossicles.

FIGURE 3. Sclerothyone nozawai (Mitsikuri, 1912) n. comb. Holotype. SEM of table ossicles of A. Tube feet; B. Body wall; C. Introvert.