Woosukia subhexagona ( Ortmann, 1890 )

Min, Bum Sik, Seo, Ji Eun, Grischenko, Andrei V., Lee, Sang-Kyu & Gordon, Dennis P., 2017, Systematics of some calloporid and lacernid Cheilostomata (Bryozoa) from coastal South Korean waters, with the description of new taxa, Zootaxa 4226 (4), pp. 471-486 : 477-479

Woosukia subhexagona ( Ortmann, 1890)

( Figs 8, 9 )

Schizoporella subhexagona Ortmann, 1890: 51 , pl. 4, fig. 3.

Schizobrachiella subhexagona: Harmer, 1957: 1026 (part); Hirose, 2010: 128, pl. 219A–E.

Material examined. MBRBKSP032, Udo Island, Jeju-do, 21 December 2015, 20– 25 m, collected by H.J. Yang and B.S. Min.

Description. Colony encrusting, unilaminar, up to 30 mm or more in diameter. Zooids subhexagonal, arranged in regular quincunx, rounded distally, truncate or with a rounded or angled margin proximally. Frontal shield dimpled by numerous evenly distributed simple pseudopores that continue as a double or triple row around the orifice; a small area just proximal to the sinus may be devoid of pores; 78–102 (mean 93) frontal-shield pseudopores in zone of astogenetic repetition. Orifice nearly circular, or a little wider than long, the large anter curving on both sides towards obliquely sloping ‘shoulders’ on which are set long narrow condyles with a slightly sinuous profile; sinus shallow and rounded, occupying about a third of the width of the proximal orificial margin. No oral spines. No avicularia. Ooecium large, generally as wide as an autozooid, occupying a considerable part of the distal zooid; the maternal orifice much wider, and a little longer, than autozooidal orifices. Female zooid about as wide and as long as an autozooid but with a shorter frontal shield suborally, the shield perforated as in autozooids. Ooecial skeletal surface endooecial, densely and variably perforated by generally irregularly shaped pseudopores, these a little larger toward to ooecial periphery, where the boundary is marked by a thin line where the membranous ectooecium attaches. Ancestrula not seen.

Measurements. ZL 560–703 (622) µm, ZW 393–521 (474) µm; OL 184–221 (202) µm, OrW 191–223 (203) µm; ♀ OrL 144–201 (198) µm, ♀ OrW 269–325 (291) µm; OoL 347–423 (386) µm, OoW 390–490 (378) µm.

Remarks. At least two other species have been confused with W. subhexagona , but which are very likely congeneric. Harmer (1957) illustrated material from Sumbawa, Lesser Sunda Islands, Indonesia . If his illustrations are accurate, then this material is clearly a different species, having far fewer frontal-shield pseudopores (c. 60) and, as also mentioned in the description, a central (not merely suboral) imperforate area. Harmer (1957) noted that Ortmann (1890) illustrated pores all over the frontal shield of specimens from Sagami Bay , and this is certainly the case in lectotype material illustrated by Hirose (2010) from Döderlein’s collection. The material from Indonesia also differs in the porosity of the ooecium, having radial slit-like pores arranged around the periphery. Since Harmer mentioned other material from Indonesia that showed an intermediate or mixed expression of ooecial pores, perhaps the radial slits are found in older ooecia or maybe yet another species is involved. In an encyclopedia of fauna from Japan, Mawatari (1965) depicted an ooecium like that in material from Indonesia, but his stylized drawing looks like it may have been adapted from Harmer (1957). Wass & Yoo (1983) illustrated a similar type of ooecium in material from the southern Australian continental shelf. Although having radial slits, the ooecium has a broad proximofrontal band of smooth ectooecium. The autozooidal frontal shield has only about 40 pseudopores, as well as a centrally imperforate area. Given the morphological differences among these forms and the unlikelihood of the same species being distributed from Honshu to southern Australia, especially since there is no record of invasive ability, it seems that at least three species are involved.

Distribution. Korea: Jeju Island region; Japan: Sagami Bay and Sagami Sea; 20–270 m on hard substrata.

Figures

FIGURES 8, 9. Woosukia subhexagona (Ortmann, 1890) n. gen., Jeju Island. 8, Autozooids and an ovicellate female zooid with a dimorphic orifice; scalebar 500 µm. 9, Close-up of ooecia and dimorphic orifices; scalebar 400 µm.