Two specimens (124.0-148.6mm standard length) of a scorpionfish, Idiastion pacificum Ishida and Amaoka, 1992, were collected from the central North Pacific, representing the first record of the species from this area. This finding extends the distributional range of Idiastion pacificum, which was previously known only from the Kyushu-Palau Ridge, western North Pacific. This study provides new morphological data and a color photograph of I. pacificum based on these two additional specimens, with a comparison to Idiastion kyphos Eschmeyer, 1965.
Upeneus guttatus (Day, 1868) (Perciformes: Mullidae) is recorded from Japan for the first time on the basis of 21 specimens (57.8-139.5mm standard length) collected from Kagoshima Prefecture, southern Japan. These specimens also represent the first records of U. guttatus from East Asia and the northernmost records in the western Pacific Ocean; this species has not previously been recorded north of the Philippines. The Japanese specimens of U. guttatus, described herein in detail, and 14 specimens from the Indo-West Pacific are compared with 33 specimens of U. japonicus (Houttuyn, 1782).
We reclassify and redescribe the apodid holothurian Scoliodotella uchidai Oguro, 1961 as Scoliorhapis lindbergi (D'yakonov in D'yakonov et al., 1958) comb. nov., based on newly collected topotypes of the former from Akkeshi Bay, Japan. We confirm the previously proposed, but not widely recognized, synonymy between these two nominal species. Scanning electron microscopy of 968 sigmoid bodies from 17 specimens of S. lindbergi from Akkeshi Bay revealed that 12.0% of them possessed spinelets, which varied in size, number, and arrangement, and that 0.8% were anchor-shaped, resembling ossicles characteristic of Synaptidae.
A new asterinid, Disasterina akajimaensis sp. nov., is described from a specimen collected at Akajima Island, the Ryukyu Islands, Japan. It is clearly distinguishable from its five congeners by the following diagnostic characters: body relatively low and flat, uncalcified interradial areas conspicuous on ventral interradii, papulae numerous in center of disc, abactinal plates mostly lacking spinelets, inferomarginal plates with 2-4 spinelets, actinolateral plates with 1 spine, oral plates with 4-5 oral spines and no suboral spine, adambulacral plates with 1-3 furrows and 1 subambulacral spine. This is the first report of this genus from Japanese waters. Notes on the genus Disasterina and a tabular summary of the characters of the currently known species are also given.
The systematic position of the monotypic eubrachyuran genus Pseudopinnixa Ortmann, 1894, which traditionally has been placed in the family Pinnotheridae, is reassessed on the basis of the adult morphology. The structure of the thoracic sternum, third maxilliped, and male abdomen strongly suggests a close relationship between Pseudopinnixa and members of the subfamily Gaeticinae in the family Varunidae. Consequently, the genus is transferred to this varunid subfamily. This assignment is also supported by the first zoeal morphology. The type species, P. carinata Ortmann, 1894, is redescribed and illustrated in detail.
Gammarus koreanus Ueno, 1940, which was originally described from the Korean Peninsula, is recorded from fresh-waters of the Goto Islands, Japan. This is the first record of its occurrence in Japan. Molecular analyses using partial sequences of the 28S rRNA gene strongly support the identity of Japanese populations with G. koreanus. The Japanese specimens differ from the original description of this species in the following features: antenna 2 lacking calceoli, inner margins of inner and outer rami of uropod 3 with plumose setae, and outer margin of outer ramus of uropod 3 without plumose setae. These differences are regarded as intraspecific variation.
Ten new species of the genus Amblyops (Crustacea: Mysida: Mysidae: Erythropinae) from waters neighboring East Asia and Australia, mainly Japanese waters, are described. The newly established species are A. amamiensis, A. australiensis, A. izuensis, A. kashimensis, A. manazuruensis, A. okinawensis, A. pacificus, A. sagamiensis, A. surugensis, and A. timorensis, bringing the total number of species in this genus to 22. Amblyops pacificus sp. nov. has been reported from the northern North Pacific under the name A. abbreviatus (G. O. Sars, 1869). It is instituted herein as a new species because it differs distinctly from that otherwise northern North Atlantic species in the characters of the eyeplates, antennal scale, and telson. In addition to these 10 new species, four unidentified species are also mentioned. A key to all the named species of Amblyops is given.
Adults of four species of the genus Caligus (Copepoda: Caligidae) were found in plankton samples collected from the coasts of Japan and Thailand: Caligus chiastos Lin and Ho, 2003 from the Gulf of Thailand; C. latigenitalis Shiino, 1954 from the Suo-nada basin of the Seto Inland Sea, Japan; C. undulatus Shen and Li, 1959 off the island of Mukaishima, Hiroshima, Japan; and C. longiramus sp. nov. from Amami Island, Kagoshima, Japan. The first two species respectively represent the first reported occurrences in plankton samples, although the third species has been encountered frequently in the pelagic fauna in Japanese waters. Caligus chiastos also represents the first report of pelagic caligids from Thailand. The present study provides support to the hypothesis that some species of Caligus occurring in the plankton alternate between two life modes: on their host fish and free in the water column. Caligus longiramus sp. nov. can be distinguished from its congeners by the following combination of features: (1) antennule long with its distal segment twice as long as its proximal one; (2) dentiform process of proximal segment of antenna small and blunt; (3) sternal furca long with sharp tines; (4) exopod of leg 4 armed with I-0; I, III elements; and (5) proximal outer spine on exopod of leg 2 longer than next more distal spine and crossing over it posteriorly.
Two new species of cyclopoid copepod, Halicyclops setiformis and H. itohi, are described based on female specimens from the Tama River estuary in Tokyo Bay, central Japan. One of the defining characteristics of H. setiformis is the presence of a setiform lateral element on the third exopodal segment of legs 3 and 4. Among its congeners, only H. blachei Lindberg, 1952 has similar elements; H. setiformis differs from it in the shape of the third endopodal segment of leg 4. This new species is considered carnivorous based on the occurrence of a specimen biting a nematode and the presence of stout, claw-like spines on the oral appendages. The second new species, Halicyclops itohi, is distinguishable from most of its congeners in the absence of lateral protuberances on the genital double-somite, the absence of a terminal accessory seta on the caudal ramus, and a 18.104.22.168 spine formula on the third exopodal segment of legs 1-4. Congeners sharing these three morphological characteristics differ variously from H. itohi in their caudal ramus shape, urosomal frills, antennal setal number, medial elements of the third endopodal segment of leg 4, and/or the shape of leg 5. The hitherto known Halicyclops species from Japan are briefly reviewed, and a key to the Japanese species is presented to resolve previous questionable identifications.
Echinoderes ohtsukai sp. nov. is described from an intertidal flat in the Seto Inland Sea, Japan, based on observations with light and scanning electron microscopy. Echinoderes ohtsukai is characterized by 1) a short middorsal spine on segment 4; 2) lateroventral tubules on segments 5 and 8; 3) short laterodorsal tubules on segment 10; 4) a trunk 315-395μm long; 5) a lack of lateral terminal accessory spines in both sexes; and 6) lateral terminal spines of about 50% trunk length. The species has modified type-II glandular cell outlets, which have previously been reported among congeners only in E. rex Lundbye, Rho and Sorensen, 2011 from the Korea Strait.