The genus Bebryce (Cnidaria, Octocorallia, Plexauridae) at Japan, with descriptions of three new species

Abstract Three new deep-water species of Bebryce from Japan are described and depicted using Scanning Electron Microscopy: Bebryce otsuchiensis sp. n., Bebryce rotunda sp. n., and Bebryce satsumaensis sp. n. Bebryce studeri Whitelegge, 1897, was reported from Japanese waters for the first time, bringing the total of Japanese Bebryce species to six. Five of these six species seem to be endemic to Japanese waters and all occur in deep water up to 213 m. A key to the Bebryce species is presented.


Introduction
Bebryce Philippi, 1841, is a genus of octocorals, which is distributed in tropical to subtropical waters in the Atlantic and Indo-Pacific Oceans. Two Japanese endemic subtropical deep-water species of Bebryce have been reported from the Ogasawara Islands (= Bonin Islands), both with rosettes with warty, rounded, or bristle-like projections: B. bocki Aurivillius, 1931 and B. boninensis Aurivillius, 1931. These two species have been re-described in a revision by Bayer and Ofwegen (2016), in which they remained the only Bebryce species described from Japanese waters. Meanwhile, other species have been reported from Japan, and B. bocki has been reported outside Japan (Bayer and Ofwegen 2016).
Here we present three additional, new species, and report the finding of B. studeri Whitelegge, 1897 in Japanese waters, a species previously known from Funafuti, New Caledonia, Indonesia, and the Philippines (Bayer and Ofwegen 2016). Bebryce bocki seems to be the most common Bebryce species in Japanese waters, whereas B. boninensis was never found again.

Material and methods
Material was collected by dredging, trawling or fishing net onboard research vessels RV Tansei-maru, University of Tokyo and Japan Agency for Marine-earth Science and Technology, RV Yayoi, the University of Tokyo, RV Shinyo-maru, Tokyo University of Marine Science and Technology, and the commercial fishing boat Kiryo-maru during the years [2003][2004][2005][2006][2007][2008][2009]. Depths of each station are converted to depth range in meters from shallow to deep, also when it is towed from deep to shallow if that would be indicated on the sampling label with original provenance data. We also examined historical museum material of the Zoological Museum University of Copenhagen, Denmark (ZMUC); University Museum of University of Tokyo, Japan (UMUT); and type material of B. bocki and B. boninensis of the Museum of Evolution, Uppsala, Sweden (UUZM) (Figure 1). Specimens were collected from a depth between 67.1 and 213 m.
Of each specimen, a small piece of the distal part of a branch was dissolved in a 4% household bleach solution to isolate sclerites. These sclerites were washed with demineralised water, dried on a hot plate, mounted on SEM stubs, and coated with Pd/Au for SEM imaging. For this, either a JEOL JSM6490LV scanning electron microscope was operated at high vacuum at 10 kV, or a JEOL JSM6510LA scanning electron microscope with a Quick Carbon Coater SC-701C, SANYU ELECTRON was used. For terminology, see Bayer et al. (1983).
Descriptions of old Japanese material collected by Japanese used "hiro" (Japanese fathom) as the depth unit. One Japanese fathom (hiro) is usually 1.43 m, occasionally 1.51 m, whereas, it is 1.818 m for the length unit on land. The old depth unit fathom is also converted to 1.8288 m. When it was not clear whether the collector used fathom or hiro, the converted depth has wider ranges.
All new type material is stored in ethanol and deposited in the Cnidaria collection (RMNH Coel.) of Naturalis Biodiversity Center, Leiden, the Netherlands (NBC).
Remarks. Apparently this is the most common Bebryce species in sub-tropical to temperate Japanese waters, in a depth range of 97-213 m.

Bebryce boninensis Aurivillius, 1931 Figures 1, 2b
Bebryce boninensis Aurivillius, 1931: 200, fig. 39, pl. 4 fig. 3 (Bonin Is., Japan); Matsumoto 2014:    Remarks. It cannot be excluded that this species is synonymous with B. bocki. Its sclerites are very similar and it only differs in lacking the asymmetrical rosettes at the calyx margin. These sclerites may perhaps fall off easily, which would explain why the species was never reported again. The distance between Chichijima Island (type locality of B. bocki) and Anijima Island (type locality of B. boninensis) is ca. 800 m within the Anijima Strait. The recorded depth of B. boninensis (150 m) is within the depth range of B. bocki (97-213 m). As collecting efforts at the Bonin Islands have been limited, the two species are still considered separate in the present study. Re-examination of the material studied by Matsumoto et al. (2007), proved to be B. bocki.     The sclerites of the outer surface of coenenchyme and calyces are rosettes consisting of a cup-shaped thorny projection arising from a warty base. Several of these are up to 0.10 mm long and have a widely flared calyx part of about 0.10 mm in greatest diameter with slightly serrated rim with a few blunt processes, joined by a smooth, slender stem to a warty base narrower than the calyx (Figure 3d); others do not flare out (Figure 4c). The rosettes become asymmetrical toward the calycular apertures (Figure 3e), with the calyx margin becoming elongated and forming a blade-like process that projects from the surface and surrounds the calycular aperture. These sclerites are up to 0.20 mm long.

Bebryce otsuchiensis
The deeper layer of coenenchyme contains stellate plates, 3-6 rayed forms up to 0.15 mm in the greater diameter, with a central process (Figure 4a). Most are weakly tuberculated (Figure 4a) but several are more tuberculated towards the end of the rays (Figure 4b).
Comparisons. The species mostly resembles B. harpy Grasshoff, 1999, regarding the blunt processes of the rosettes. It differs in overall having less tuberculate sclerites.
Remarks. This is the northernmost species of Bebryce. It has a very wide distribution from North to South Japan, and is only found in the warm Kuroshio Current area, in the depth range 67-143 m. This species also represents the northernmost record of the genus Bebryce, and the first from north of 39°N latitude.  The sclerites of the outer surface of coenenchyme and calyces are rosettes consisting of a cup-shaped thorny projection arising from a warty base. These rosettes are 0.10 mm tall, have a flared calyx part about 0.10 mm in greatest diameter with blunt processes (Figure 7d) or the rim of the cups is formed several strong, laciniated projections (Figure 8b). Toward the calycular apertures the rosettes become asymmetrical (Figure 7e), with the margin of the calyx becoming much elongated forming a bladelike process that projects from the surface and surrounds the calycular aperture. These sclerites are up to 0.15 mm long.
The plates of the inner coenenchyme are tuberculate disks up to about 0.15 mm in diameter with tuberculate rim and central process on one surface (Figure 8a).
Colour. The holotype is creme. Etymology. From the Latin rotundus, wheel-shaped, round, referring to the round disks of the coenenchyme.
Comparisons. Bayer and Ofwegen (2016) mentioned only two species with tuberculate disks and cup-shaped rosettes, Bebryce species A and B. thomsoni Nutting, 1910. The present species differs from these two by having disks with a smooth central part and a small process in the middle, while those of Bebryce species A and B. thomsoni have tubercles all over the disk. Th. Mortensen's Pacific Expedition 1914-1915, coll. Dr. Th. Mortensen, 15 May 1914RMNH Coel. 42079 (AKM 1092), Shin-sone bank, Danjo Is., Japan, East  China Sea,31°54.61'N,128°19.56'N,128°19.41'E,, st. GT02(2), ORI-TI chain bag dredge, coll. A.K. Matsumoto, 7 March 2008. Description. The holotype RMNH Coel. 42077 consists of a sparsely branched colony about 5 cm long and a few loose branches (Figure 2e). The calyces are placed spirally all around the slender branches, which are about 1 mm wide. The domeshaped calyces are about 1 mm wide and high.
The anthocodiae are armed with a crown and points consisting of a transverse crown with curved, rather smooth spindles up to 0.45 mm long (Figure 9a) and eight points formed by spindles 0.3 mm long (Figure 9b) placed in a chevron-like pattern beneath the tentacles. These spindles have simple tubercles and a distal spiny end. The tentacles contain flattened, dragon wing sclerites up to 0.2 mm long (Figure 9c).
The sclerites of the outer surface of coenenchyme and calyces are rosettes consisting of a cup-shaped thorny projection arising from a warty base. Several, about 0.15 mm tall, have a widely flared calyx part about 0.15 mm in greatest diameter with slightly serrated rim with some spines, joined by a smooth, slender stem to a warty base narrower than the calyx (Figures 9e, 10d). Others have a less serrated rim which does not flare out (Figure 10c). Toward the calycular apertures the rosettes become asymmetrical (Figure 9d), with the margin of the calyx becoming much elongated, forming a blade-like process that projects from the surface and surrounds the calycular aperture. These sclerites are up to 0.25 mm long.
The deeper layer of coenenchyme contains stellate plates, 4-6 rayed forms up to 0.10 mm in the greater diameter, with a central process (Figure 10a). Stellate sclerites with a prominent, thorny central process, intermediate in form between the cupshaped outer forms and the stellate plates of the deeper coenenchyme are not uncommon (Figure 10b).
Colour. The holotype is brown. Etymology. Named after the type locality, Satsuma (old name of Kagoshima prefecture).
Comparisons. The rosettes with weakly serrate rim and few spines are unique for this species within the genus. B. brunnea (Nutting, 1908) and B. cofferi Bayer and Ofwegen, 2016 resemble this species but have rosettes with more serrate rim.