Hana hanagasa, Lau, Yee Wah, Stokvis, Frank Robert, Ofwegen, Leendert Pieter van & Reimer, James Davis, 2018

Lau, Yee Wah, Stokvis, Frank Robert, Ofwegen, Leendert Pieter van & Reimer, James Davis, 2018, Stolonifera from shallow waters in the north-western Pacific: a description of a new genus and two new species within the Arulidae (Anthozoa, Octocorallia), ZooKeys 790, pp. 1-19 : 4-5

Hana hanagasa sp. n. Figures 2a, 3

Material examined.

All specimens are from Okinawa Island, Okinawa, Japan. Holotype: OKA170711-15, Canyon, Cape Hedo (26°52.326'N, 128°15.995'E), 17 m depth, coll. YW Lau, 11 July 2017 (MH845555; MH845545). Paratype 1: OKA170629-01, Iheya, Iheya Island (27°5.710'N, 128° 1.828'E), coll. R Janssen, 29 June 2017 (MH845559; MH844382). Paratype 2: OKA170711-06, Hedo Dome, Cape Hedo (26°51.125'N, 128°15.027'E), 6 m depth, coll. YW Lau, 11 July 2017 (MH845552). Paratype 3: OKA170711-07, Hedo Dome, Cape Hedo (26°51.125'N, 128°15.027'E), 6 m depth, coll. YW Lau, 11 July 2017. Paratype 4: OKA170711-08, Hedo Dome, Cape Hedo (26°51.125'N, 128°15.027'E), 10 m depth, coll. YW Lau, 11 July 2017 (MH845553). Paratype 5: OKA170711-10, Hedo Dome, Cape Hedo (26°51.125'N, 128°15.027'E), 11 m depth, coll. YW Lau, 11 July 2017 (MH845554; MH845544). Paratype 6: OKA170711-16, Hedo Dome, Cape Hedo (26°51.125'N, 128°15.027'E), 7 m depth, coll. FR Stokvis, 11 July 2017. Paratype 7: OKA170711-17, Canyon, Cape Hedo (26°52.326'N, 128°15.995'E), 16 m depth, coll. FR Stokvis, 11 July 2017 (MH845546). Paratype 8: OKA170711-20, Hedo Dome, Cape Hedo (26°51.125'N, 128°15.027'E), coll. JD Reimer, 11 July 2017 (MH845556; MH845547; MH844383). Paratype 9: OKA170818-11, Canyon, Cape Hedo (26°52.326'N, 128°15.995'E), collected by JD Reimer, 18 August 2017 (MH845558). Paratype 10: OKA170818-03, Futagami-iwa, Cape Hedo (26°52.177'N, 128°14.847'E), 22 m depth, coll. YW Lau, 18 August 2017 (MH845557; MH844384). Paratype 11: OKA170818-05, Futagami-iwa, Cape Hedo (26°52.177'N, 128°14.847'E), 11 m depth, coll. JD Reimer, 18 August 2017.

Description.

The colony consists of numerous small polyps (~50) growing on hard coral rock. Polyps are spaced apart irregularly (0.3-2.5 mm), connected by stolons that are 0.5 mm in diameter and flat thin ribbon-like in cross-section. Polyps have anthocodia fully retracted into calyces of 2.5-3 mm tall and up to 1.0 mm diameter at the widest point; calyces are slightly club-shaped or barrel shaped, wider near the distal end than at the proximal point of attachment to the stolon.

The oral disk expands into a broad circular membrane by fusion of the proximal regions of the adjacent tentacles. The margin of the oral membrane has eight broad lobes, with eight deep furrows, which run from the intertentacular margin to the mouth of the polyp, giving a plump appearance (Figure 2a). The distal two-thirds of the tentacles extend from fused margins of the oral membrane. Tentacles are long and thin, with 10 pairs of widely spaced pinnules, which are arranged in a single row on either side of the rachis.

Anthocodial sclerites are small rods with simple tubercles around margins 0.10-0.18 mm long (Figure 3a). Calyx containing small 6-radiates 0.05-0.06 mm long (Figure 3b) and table-radiates ranging 0.03-0.17 mm, giving the largest table-radiates a spindle- and sometimes club-like appearance (Figure 3c). Stolons with fused table-radiates form a flat network (Figure 3d).

The oral disk is white and the tentacles are brown in life (Figure 2a), yellowish-white in ethanol (Figure 2h). Zooxanthellate.

Morphological variation.

Paratypes are colonies consisting of 50-100 polyps, growing on hard substrates and sponges. Colonies show variations in number of pinnules, having 8-10 pairs lining either side of the rachis.

Distribution.

Northwest coast of Okinawa Island and southeast coast of Iheya Island in the East China Sea.

Remarks.

Arula and Hana are the only two genera within the family Arulidae . Arula petunia and H. hanagasa have very similar polyp morphologies with only a clear difference in polyp colour. Oral disk and tentacles of A. petunia are blue in life and white and brown in H. hanagasa , respectively. This would suggest assignment to the same genus, however, the combination of differences in genetic data and sclerite morphology indicate that they should be separate from each other at the generic level. The possibility that there are similar species or previous descriptions and reports on arulid species has previously been discussed ( McFadden and Ofwegen 2012) and so far, no reports have been made on possible congeners.

Etymology.

From the Japanese language ' hanagasa ' (花笠), the traditional Okinawan ceremonial dance headpiece worn by female performers; denoting the shape of the polyps, which resembles the flower headpiece.