Melithaea arborea Kuekenthal , 1908

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 : 6-7

Taxon classification Animalia Alcyonacea Melithaeidae

Melithaea arborea Kuekenthal, 1908 Figures 8, 9a, 10, 11

Melitodes arborea : Kükenthal 1908: 193; 1909: 59, figs 61-63, Pl. 4 fig. 26 (Japan); Kükenthal 1919: 150; 1924: 62; Hickson 1937: 122.

Material examined.

Holotype ZMH C3305, Sagami Bay (collection number in Kükenthal (1908) incorrect as 63305), coll. A. Austin.

Re-description.

Colony bushy (Fig. 9a). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 10a). These platelets are up to 0.10 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 10b). Coenenchyme with capstans (Fig. 10c), about 0.05 mm long, the bigger ones are spheroids (Fig. 10d); small clubs of similar length; spindles, 0.10-0.30 mm long, with simple or complex tubercles (Figs 10e, 11). The axis has smooth and sparsely tuberculate rods (Fig. 10f).

Color.

Red with paler polyps, sclerites orange, tentacle sclerites colorless.

Distribution.

The name of collector A. Austin could actually be Alan Owston ( Isono 1988), an English trader (import and export merchant and naturalist), who used to collect material of deep-water species. Therefore we suspect Melithaea arborea to grow in deeper water. So far it is only found in Sagami Bay (Fig. 8).

Remarks.

The colony depicted by Kükenthal (1908) could actually be the basal part of a much larger colony. As with Melithaea japonica , many sclerites are disintegrated, and therefore we could not depict the small clubs of the coenenchyme. Also, the sample available to us had hardly any polyp sclerites, since only a few tentacle rods were present (Fig. 10a). Therefore, we assume that they also had disintegrated. Kükenthal (1908) described collaret and point sclerites as being 0.20 mm long, the tentacle rods 0.15 mm long. He did not mention the presence of capstans and small clubs. We found no sclerites resembling clubs referable to calyces and only a few sclerites with a tendency to be unilaterally spinose.

According to Kükenthal (1908) the species resembles mostly Melithaea japonica . Indeed the sclerites of these two species are very similar, Melithaea japonica showed somewhat more developed unilaterally spinose sclerites and some sclerites resembling clubs. Bearing in mind the colony fragment of Melithaea arborea resembles a basal part we do not exclude the possibility Melithaea arborea and Melithaea japonica represent one and the same species. Therefore, they were given the same position in the key to species identification.