Hanabira yukibana, Lau & Stokvis & Imahara & Reimer, 2019

Lau, Yee Wah, Stokvis, Frank R., Imahara, Yukimitsu & Reimer, James D., 2019, The stoloniferous octocoral, Hanabira yukibana, gen. nov., sp. nov., of the southern Ryukyus has morphological and symbiont variation, Contributions to Zoology 88 (1), pp. 54-77 : 75-77

Hanabira yukibana , sp. nov.

Figs. 2 , 3

Clavulariidae gen. sp. Imahara et al., 2017.

Material examined. Holotype: NSMT-Co 1626, Takosaki , Iriomote Island (24.327010, 123.738290), 11 m depth, coll. YWL, 25 July 2017.

Paratypes from Takosaki , Taketomi Town, Iriomote Island (24.327010, 123.738290) : Paratype 1: NSMT-Co 1625, 11 m depth, coll. YWL, 25 July 2017. Paratype 2: NSMT-Co 1627, 11 m depth, coll. YWL, 25 July 2017. Paratype 3: NSMT-Co 1628, 11 m depth, coll. YWL, 25 July 2017. Paratype 4: NSMT-Co 1629, 10 m depth, coll. YWL, 25 July 2017. Paratype 5: NSMT-Co 1630, 10 m depth, coll. YWL, 25 July 2017. Paratype 6: NSMT-Co 1631, 12.7 m depth, coll. S Kunihiro, 25 July 2017. Paratype 7: NSMT-Co 1632, 14 m depth, coll. YWL, 25 July 2017. Paratype 8: NSMT-Co 1633, 12 m depth, coll. YWL, 25 July 2017. Paratype 9: NSMT-Co 1634, 13 m depth, coll. YWL, 25 July 2017. Paratype 10:NSMT-Co 1635, 11 m depth, coll. YWL, 25 July 2017. Paratype 11: NSMT-Co 1636, 13 m depth, coll. YWL, 25 July 2017.

Paratype 12: NSMT-Co 1637, Iriomote N, Taketomi Town , Iriomote Island (24.407805, 123.854199), 31 m depth, coll. YWL, 25 July 2017 .

Paratypes from Okinawa Island : Paratype 13:NS- MT-Co 1638, Abu , Oura Bay, Nago City (26.537756, 128.079521), 14 m depth, coll.YWL, 04 Jun 2017 . Paratype 14: NSMT-Co 1639, Hoshu , Manza, Onna Village (26.504659, 127.846604), 13 m depth, coll. YWL, 24 Jun 2017 . Paratype 15: NSMT-Co 1640, Hoshu , Manza, Onna Village (26.504659, 127.846604), 14 m depth, coll. YWL, 24 Jun 2017 . Paratype 16: NSMT-Co 1641, Zanpa, Cape Zanpa, Yomitan Village (26.441517, 127.711417), 21 m depth, coll. YWL, 24 Jun 2017 . Paratype 17: NSMT-Co 1642, Hedo Dome, Cape Hedo, Kunigami Village (26.852091, 128.250450), 34 m depth, coll. YWL, 11 Jul 2017 . Paratype 18: NSMT-Co 1643, Manza Beach , Manza, Onna Village (26.502957, 127.841909), 17 m depth, coll. YWL, 16 Jul 2017 . Paratype 19: NSMT-Co 1644, Manza Beach , Manza, Onna Village (26.502957, 127.841909), 17 m depth, coll. YWL, 16 Jul 2017 . Paratype 20: NSMT-Co 1645, Manza Rock , Manza, Onna Village (26.504522, 127.843748), 16 m depth, coll. YWL, 12 Sep 2017 . Paratype 21: NSMT-Co 1646, Manza Rock , Manza, Onna Village (26.504522, 127.843748), 11 m depth, coll. YWL, 12 Sep 2017 . Paratype 22: NSMT-Co 1647, Hoshu , Manza, Onna Village (26.504659, 127.846604), 33 m depth, coll. JDR, 13 Nov 2017 . Paratype 23: NSMT-Co 1648, Crossline , Seragaki, Onna Village (26.508734, 127.881453), 32 m depth, coll. JDR, 14 Nov 2017 . Paratype 24: NSMT- Co 1649, Mini Dream Hole , Manza, Onna Village (26.509833, 127.854006), 29 m depth, coll. JDR, 14 Nov 2017 . Paratype 25: NSMT-Co 1650, Nakagusuku Bay , Nakagusuku Town (26.2627778, 127.825278), 17 m depth, coll. Y Kushida, 04 Aug 2018 . Paratype 26: NSMT-Co 1651, Oura SW, near Cape Henoko, Futami, Oura Bay , Nago City (26.529373, 128.047446), ca. 10m depth, coll. M Obuchi & T Fujii, 4 Mar 2011 . Paratype 27: NSMT-Co 1652, Motobu , off Yamakawa, Motobu Town (26.679389, 127.879222), 15 m depth, coll. Y Imahara, 27 Oct 2011 . Paratype 28: NSMT-Co 1653, Motobu , off Yamakawa, Motobu Town (26.679389, 127.879222), 15 m depth, coll. Y Imahara, 27 Oct 2011 .

Description. The holotype colony is attached to a sponge, which was fragmented into three pieces during sampling, although, this species is not always an epibiont and can be attached to other hard substrates. Small groups of polyps are attached by stolons to the sponge tissue (total ~10 polyps). Polyps are approximately 2–3 mm in diameter expanded and are spaced apart irregularly (from ~ 0.5 mm up to ~ 2 cm) and connected through flat and ribbon-like stolons that are 1 mm at the widest and 0.2 mm at the narrowest point. Anthocodiae can retract fully into cylindrical to barrel-shaped calyces, which are 1.5–2.5 mm in height and up to 1 mm in width; calyces do not retract into the stolon. Tentacles have pseudopinnules arranged adjacent to one another along either side of the tentacle rachis (~18 pseudo-pairs); when stained with methylene blue, the outline of the tentacles can be observed. A structure that seems to be the pinnule axis can be seen, although notches, which can distinguish the adjacent pinnules, are not observed in the contour of the tentacle (fig. 2e). In life the tentacles are elliptical to petal-shaped and the polyps have a pale, green-gold and white sheen. This could be caused by refraction on the minute sclerites, as described in Alderslade & McFadden (2007) (fig. 2a). Sclerites of anthocodiae are platelets with a distinct median waist (0.01–0.02 mm) and small smooth rods (0.1– 0.2 mm), with the tentacles only having the type of platelets as seen in the anthocodiae (fig. 3b, c). Sclerites of calyces are rods, which are larger than the anthocodial rods, that are prickly and warty (0.2–0.3 mm) (fig. 3a). Sclerites of the stolon are a tubular network of fused sclerites (fig. 3d, e). The polyps are zooxanthellate.

Morphological variation. Polyp density in H. yukibana is variable, as is also the broadness of the stolons (0.1–1.1 mm). Tentacles are not all elliptical in life; some specimens have a more pointed shape at the distal part of the tentacle. The number of pseudopinnules ‘paired’ alongside the tentacle rachis varies within a range of 15–31 ‘pairs’. The colour of the polyps is also very variable; in exception of paratypes 15, 16 and 25, all specimens have a clear recognisable sheen. The sheen is thought to be caused by refraction from the platelet sclerites in the tentacles (Alderslade & McFadden, 2007); usually green-gold and/or white. Paratypes 15, 16 and 25 do not lack the minute platelet sclerites but instead have a lower platelet density in the tentacles and only have this typical sheen (white) at the far distal part of their tentacles. Live specimens were overall brown in colour.

Etymology. From the Japanese language ‘yukibana’ (ḜAE), meaning ‘snow flower’; denoting the resemblance of the sheen of the polyps (including tentacles) to the shimmer of snowflakes or snow crystals.

Habitat. Colonies encrust hard substrates with their stolons. Common substrates are rock, sponges, coral rubble and shells.

Distribution. Southwestern Japan, southern Ryukyu Islands, around Okinawa Island and the north and west coasts of Iriomote Island in the East China Sea. Specimens were collected from depths of 10– 35 m.

Figures

FIGURE 2 In situ photographs of the three main polyp variations seen in Hanabira yukibana, gen. nov., sp.nov.; variation A: a) NSMT Co 1626, holotype and b) NSMT Co 1625, paratype 1; variation B:c) NSMT Co 1637, paratype 12; variation C: d) NSMT Co 1633, paratype 8. Images of Hanabira yukibana, gen. nov., sp. nov., holotype, NSMT Co 1626:e) stained with methylene blue to accentuate pseudopinnules of the tentacles and f) colony preserved in ethanol.Scale bar:1 mm.

FIGURE 3 Sclerite types seen in Hanabira yukibana, gen. nov., sp. nov., NSMT Co 1626, holotype; a) spindles of calyx (scale bar: 0.1 mm), b) anthocodial platelets (scale bar: 0.01 mm), c) anthocodial rods (scale bar: 0.1 mm), d) fused clump of stolon (scale bar:0.1 mm).NSMT Co 1637, paratype; e) fragments of stolon (scale bar:0.1 mm).