Alcyonidium busanensis, Seo & Chae & Winston & Zágoršek & Gordon, 2018

Seo, Ji-Eun, Chae, Hyun Sook, Winston, Judith E., Zágoršek, Kamil & Gordon, Dennis P., 2018, Korean ctenostome bryozoans-observations on living colonies, new records, five new species, and an updated checklist, Zootaxa 4486 (3), pp. 251-283 : 258-259

Alcyonidium busanensis n. sp.

( Figs 5 , 6 )

Etymology. Pertaining to Busan, the geographical locality where the species was found.

Material examined. Holotype: MBRBKH6, Namuseom Island, front of Dadaepo Harbor, Busan, southern Korea, 35.0250° N, 129.2650° E, 68 m, 6 June 2017 . Paratype: MBRBKP6, same data as holotype .

Description. Colony begins as encrusting layer on shell substratum where it soon develops thick mound-like form. Eventually a mature colony develops that consists of firmly gelatinous narrow cylindrical brown branches (3–5 mm diameter) with lighter, more-translucent pointed tips that may bifurcate to produce more branches ( Fig. 5A, B ). Branching colonies up to 10–20 cm in size. Zooids small and erect, rounded-hexagonal to polygonal in outline, with deep bodies and round orifices on small papillae ( Fig. 5B, C ). Mean orifice diameter 0.056 mm (range 0.012–0.072 mm, N = 6). Zooid length, mean 0.438 mm (range 0.360–0.540 mm, N = 6); zooid width, mean 0.306 mm (range 0.234–378 mm, N = 6). A few kenozooids present between autozooids. Colonies found in early June mature with vigorous branch growth and sexually reproductive. Zooid walls in growing tips translucent enough to see the near-vertically positioned whitish retracted polypides as well as clusters of red-orange embryos and developing larvae being brooded in empty zooids ( Fig. 6A, B ). Freed larvae coronate ( Fig. 6A–D ), swimming toward light in spiral fashion at first, then sinking to the bottom, but in the lab all died before metamorphosing. Polypides with 16 tentacles.

Remarks. This species differs from any branching species described from the region. Although both it and the Japanese species Alcyonidium sagamianum Mawatari, 1953 have the form of some branching taxa of the greenalgal genus Codium (d’Hondt & Mawatari 1986) , A. sagamianum has larger branches with rounded tips, is orange in life instead of brown like A. busanensis n. sp., its surface is covered by minute mamillae, and it has 20 tentacles. Kenozooids few in number in contrast to the species described above. Unlike those of Alcyonidium bullitum n. sp., zooids of A. busanensis n. sp. are not transparent or even translucent except at growing branch tips. The cylindrical branches of A. busanensis are brown, not tan, and do not form massive encrustations like those of A. pulposum n. sp. or leafy expansions like A. diaphanum alcilobatum d’Hondt & Mawatari, 1986 . The species also lacks the thickened core found in Alcyonidium pulposum n. sp.

Distribution. SE Japan Sea on fishing net, trawled at 68 m depth, off Namuseom Island, collected from fishing boat docked at Dadaepo Harbor, Busan, Korea.

Figures

FIGURE 5. Alcyonidium busanensis n. sp., Namuseom Island, South Sea (MBRBKH6). A. Live colony removed from fishing net. B. Another live colony showing branching pattern. C. Branch of live colony showing orange clusters of developing embryos inside some zooids. D. Colony surface showing zooid outlines, relatively small orifices, and clusters of embryos. Scale bars: A = 5 cm; C = 3 mm; D = 0.65 mm.

FIGURE 6. Alcyonidium busanensis n. sp., Namuseom Island, South Sea (MBRBKH6). A. Larvae being liberated from zooids. B. Ciliated larva. C–H. Compound-microscope images of living and preserved material. C. Cluster of developing embryos and larvae, removed from zooid. D. A ciliated larva and a developing embryo. E. Embryo magnified. F. Part of branch surface showing autozooids and kenozooids. G. Autozooids in partial side view showing small orifices. H. Retracted polypide. Scale bars: A = 4 mm; B = 0.60 mm; C–E = 0.20 mm; F = 0.44 mm; G = 0.30 mm; H = 0.14 mm.