Melithaea abyssicola ( Kuekenthal , 1909)

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 : 4-5

Taxon classification Animalia Alcyonacea Melithaeidae

Melithaea abyssicola ( Kuekenthal, 1909) Figures 1, 2, 3, 4, 5, 6, 7, 8

Acabaria modesta var. abyssicola : Kükenthal 1909: 68 (Sagami Bay, Japan); Kükenthal 1919: 184; 1924: 79; Aurivillius 1931: 28 (Sagami Bay, 400-500 m).

? Acabaria modesta abyssicola: Rho et al. 1980: 55 (Korea Strait).

Material examined.

Holotype ZSM 20040057, Sagami Bay, 600 m, coll. Doflein 1904/05; previously unidentified museum material: BMNH 1921.10.26.5, Misaki, Sagami Bay, 333 fms (609 m), coll. A.V. Insole, May 1921; UMUTZ-CnidG-21, Gokeba, Sagami Bay, 150-20 hiro (227-29 m), coll. K. Aoki, 18 June 1902; UMUTZ-CnidG-28, Kahiwajima Is., Tosa, Kochi Prefecture, coll. K. Kinoshita, June 1909; UMUTZ-CnidG-29, same data as UMUTZ-CnidG-28; UMUTZ-CnidG-30, same data as UMUTZ-CnidG-28; UMUTZ-CnidG-33, same data as UMUTZ-CnidG-28; UMUTZ-CnidG-101, St.5, 170 fms (possibly Japanese fms) (243-257 m), coll. I. Ijima, 2 April 1895; UMUTZ-CnidG-232, same data as UMUTZ-CnidG-28; RMNH Coel. 41900 (AKM 430), Zeni-su, off Izu Islands, 33°53'N 138°43'E, R/V Tansei-maru, KT04-06, st. ZN-3, 267.3-288.3 m, coll. A.K. Matsumoto, 3 April 2004; RMNH Coel. 41901 (AKM 571), Otsuki, Tosa, Kochi Prefecture, 32°43'N, 132°48'E, local fishermen’s boat, Kiryo-maru, st. 3, coral-net, 84.75-83.1 m, coll. A.K. Matsumoto, 7 October 2004;?BMNH 1921.10.26.24-2, Misaki, Sagami Bay, 500-600 fms (715-1097 m), coll. A.V. Insole No. 45.

Description.

Colony branched in one plane with few anastomoses (Fig. 1a). Points with slightly bent spindles up to 0.17 mm long, distal end with more developed tubercles (Fig. 2a). Collaret with bent spindles up to 0.30 mm long, middle part with more developed tubercles (Fig. 2b). Tentacles with platelets, the larger ones crescent-shaped with irregular projections (Fig. 2c). These platelets are up to 0.15 mm long. Pharynx with straight spiny rods, up to 0.05 mm long (Fig. 2d). Coenenchyme with predominantly capstans (Fig. 3a), double disks (Fig. 3b) and disk spindles (Fig. 3c), 0.05-0.10 mm long, and small clubs of similar length (Figure 2e). Spindles, 0.10-0.20 mm long, with simple tubercles, are also present (Fig. 3d); some sclerites are intermediate between clubs and spindles (Fig. 3e). The calyces with additional clubs, up to 0.14 mm long (Fig. 2f).

Color.

Colony white, sclerites colorless.

Variation.

RMNH Coel. 41900, UMUTZ-CnidG-28 (Fig. 1d), UMUTZ-CnidG-30, UMUTZ-CnidG-33, RMNH Coel. 41900 and BMNH 1921.10.26.24-2 are yellow with yellow sclerites; UMUTZ-CnidG-21, UMUTZ-CnidG-101 and UMUTZ-CnidG-232 are orange colonies; UMUTZ-CnidG-29 is red. RMNH Coel. 41901 is orange with red polyps (Fig. 1b), polyp sclerites pink, all others yellow. The sclerites of RMNH Coel. 41901 are similar to the holotype (Figs 4, 5) but it has somewhat longer coenenchymal spindles, up to 0.25 mm long (Fig. 5d).

Distribution.

Melithaea abyssicola occurs in Sagami Bay, off the Izu Islands, and Tosa (Kochi Prefecture)(Fig. 8).

Remarks.

Kükenthal (1909) probably made this a variety of Acabaria modesta Kükenthal, 1908 because the colonies and sclerites of these two species have the same color. However, morphologically the sclerites of these two species are completely different by Melithaea modesta lacking clubs, double disks and disk spindles.

The species resembles Melithaea sagamiensis sp. n., but differs in having much smaller double disks, up to 0.05 mm long.

We have tentatively included BMNH 1921.10.26.24-2 (Fig. 1c) in Melithaea abyssicola as it was collected together with BMNH 1921.10.26.5 by the same collector at the same locality, only at different depths. However, the specimen has clubs and disk spindles but lacks the double disks and shows sclerite damage caused by formalin (Figs 6, 7).