Melithaea isonoi, Matsumoto, Asako K. & van Ofwegen, Leen P., 2015

Matsumoto, Asako K. & van Ofwegen, Leen P., 2015, Melithaeidae of Japan (Octocorallia, Alcyonacea) re-examined with descriptions of 11 new species, ZooKeys 522, pp. 1-127 : 17-19

Taxon classification Animalia Alcyonacea Melithaeidae

Melithaea isonoi sp. n. Figures 28c, 33, 34, 35

? Acabaria sp. A: Aguilar-Hurtado et al. 2012: 63, fig. 7 (Okinawa).

Material examined.

Holotype UMUTZ-CnidG-34, Coral Reef, Cape Chinen, Okinawa Prefecture, Japan, 15 April 1901; paratype UMUTZ-CnidG-256, same data as holotype.

Description.

The holotype is 12 cm long and 11 cm wide, branching is in one plane and a holdfast is lacking (Fig. 28c). The stem is 10 mm wide, the end branches only 2 mm wide. The colony has no anastomoses. The polyps are situated biserially on the branches, the calyces are dome-shaped, and the polyps retracted.

Points with slightly bent spindles up to 0.20 mm long, distal end with leaves (Fig. 33a). Collaret with bent spindles up to 0.20 mm long, middle part with more developed tubercles (Fig. 33b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 33c). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 33d). Coenenchyme with capstans (Fig. 34a), and unilaterally spinose spheroids, 0.05-0.10 mm long (Fig. 34b). Furthermore spindles are present, 0.10-0.25 mm long (Fig. 34c). All with simple and complex tubercles. The calyces with additional leaf clubs, up to 0.20 mm long (Fig. 33f). The axis has smooth and sparsely tuberculate rods (Fig. 33e).

Color.

The colony is orange as are most sclerites; a few are yellow colored.

Distribution.

Only known from Okinawa Prefecture (Fig. 35). The material is probably collected during the Ryukyu (= Okinawa) expedition by K. Mitsukuri and I. Ikeda, in April, 1901.

Etymology.

The species is named after the late Prof. Naohide Isono who has worked on Japanese zoological history from the Edo to Meiji period, in appreciation of informing the first author about the collectors data in this publication.

Remarks.

The species resembles Melithaea japonica but differs in having leaf clubs in the calyces. It resembles Melithaea tenuis regarding the unilaterally spinose spheroids, but it has longer spindles in the coenenchyme. It could be Acabaria sp. A. of Aguilar-Hurtado et al. (2012), but in that case we must accept that these authors did not illustrate the remarkable unilaterally spinose spheroids that we found among the sclerites. The “spines” of these spheroids are very rounded, hardly resembling spines. However, a more appropriate term than spinose spheroids is not available ( Bayer et al. 1983). Moreover, all colonies of Aguilar-Hurtado et al. (2012) had anastomoses while Melithaea isonoi has none.