A new species of triplefin (Tripterygiidae), Enneapterygius phoenicosoma, is described on the basis of 71 type specimens (17.2-37.2mm standard length: SL) from southern Japan. An additional five specimens from the Caroline Islands and Vanuatu are also identified as belonging to this species. Males of the new species have the same distinct nuptial coloration as males of the Hawaiian endemic species E. atriceps (Jenkins, 1903). Comparisons of the present material with the holotype and 46 non-type specimens of E. atriceps show, however, that E. phoenicosoma differs from the latter in having a simple nasal tentacle (vs a bilobed tentacle in E. atriceps); lower counts of the anal-fin soft rays (16-18, mode 17 vs 19-21, 19); second dorsal-fin spines (11-13, 12 vs 12-15, 14); scale rows in longitudinal series (32-35, 33 vs 35-37, 36); and pored lateral-line scales (16-19, 17 vs 17-20, 19); a higher count of the pectoral-fin rays (15-17, 16 vs 14-17, 15); and several morphometric features, including the lengths of the dorsal-fin spines and rays, the second dorsal-fin base, and the anal-fin base. The new species grows larger than E. atriceps (largest recorded size, 37.2mm SL vs 26.9mm SL in E. atriceps).

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We examined four specimens of caristiids from the Ogasawara Islands, southern Japan, and identified two species of the genus Platyberyx: P. andriashevi (Kukuev, Parin and Trunov, 2012) and P. rhyton Stevenson and Kenaley, 2013. The three specimens of P. andriashevi represent the first records of this species in Japan. We propose a new Japanese name for the species and present morphological data on these recently collected specimens. Platyberyx rhyton was previously known from only two specimens from off northeastern Japan. We provide morphological data for the third recorded specimen of this species and present a key to the five species of Caristiidae currently known from Japan.

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A single specimen (25.8mm standard length) of a serranid fish, Liopropoma tonstrinum Randall and Taylor, 1988, was collected from Minami-daito Island in the Daito Islands, southern Japan. This species was previously known based on specimens from Christmas Island in the eastern Indian Ocean, and various islands in the Pacific Ocean, including the Society Islands, American Samoa, Fiji, New Caledonia, Indonesia, Palau, Micronesia, the Marshall Islands, and Wake Island, as well as from underwater photographs taken in the Mariana Islands and southern Japan. Thus, the present specimen represents the first record from Japan based on a voucher specimen, as well as the northernmost specimen-based record of this species up to now.

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A specimen (184mm SL) of the rare neobythitine ophidiid Epetriodus freddyi Cohen and Nielsen, 1978, the only known species of its genus, was collected in the Hyuga-nada basin, southwest of Shikoku Island, Japan, at a depth of 1,501-1,516m in 1999. It was identified by its unique possession of needle-like teeth on both jaws as well as the vomer and palatines, and the following combination of characters: 25 pectoral-fin rays fully joined by membranes; 8 caudal-fin rays; 21 long gill rakers on the first arch; eye diameter about half snout length; two median basibranchial tooth patches; short, sharp opercular spine; and two filamentous pelvic-fin rays originating below preopercle. This species has been reported only from South Africa, Mozambique, Western Australia, and the French territory of Wallis and Futuna in the Southern Hemisphere. Thus, the present specimen represents the first record of the genus and species in the Northern Hemisphere.

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A new species of the spongicolid shrimp genus Spongicola, S. teres sp. nov., is described and illustrated on the basis of a single male specimen collected from the Society Islands, French Polynesia, South Pacific Ocean, at a depth of 650-800m. It appears closest to S. depressus Saito and Komai, 2008 and S. levigatus Hayashi and Ogawa, 1987 among the seven known congeneric species in having a reduced armature of the carapace and third pereopod, but the more developed rostral ridge, extending onto the gastric region of the carapace, distinguishes the new species from the latter two species. The armature of the telson and the development of the grooming apparatus of the first pereopod are also useful in differentiating these three species. An emended identification key to the species of Spongicola is provided.

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Anisarthrus okunoi sp. nov., an abdominal parasite of the hinge-beak shrimp Rhynchocinetes uritai Kubo, 1942, is described from Awaji Island, central Japan. The new bopyrid, the second species of Anisarthrus, is distinguished from A. pelseneeri Giard, 1907 from Boulogne, France, by the lateral plates of the concave side being smaller than those of the convex side, the large, lanceolate pleopods 1-2 and slightly bilobed pleopods 3-4, the simple, bulbous pleotelson in the female, the lack of eyes, and the rounded posterior margin of the pleotelson in the male. This is the first record of bopyrid infestation of any member of the family Rhynchocinetidae in the world.

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We describe two shallow-water species of Agathotanais, A. misakiensis sp. nov. and A. toyoshioae sp. nov., from Japan. Agathotanais misakiensis was collected from 211-493m depth in the Sagami Sea, North Pacific Ocean. It closely resembles A. ghilarovi Kudinova-Pasternak, 1989, but differs in having shorter pereonites 3 and 4, all pleonites narrower than pereonite 6, and a shorter article 3 in the antennule. Agathotanais toyoshioae, collected from 95m depth in the Genkai Sea, Sea of Japan, is very similar to A. spinipoda Larsen, 1999. The former can be distinguished from the latter by its narrower pleonites, the presence of a ventral keel on pleonites 1 and 2, and the presence on the basis and absence on the carpus and propodus of small spines on pereopods 4-6.

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A new species of poecilostome cyclopoid copepod, Pennatulicola piscatorius n. sp., is described as an associate of the pennatulacean genus Pteroeides from Tokyo Bay, Japan. The new species is distinguishable from its congeners by the following combination of features: exopod of leg 5 with conical inner process arising 38% of way distally, maxillule with three apical setae, and basis of legs 1-4 with a simple outer seta. This is the first record of the genus Pennatulicola in East Asia.

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A new species of ectosymbiotic branchiobdellidan, Cirrodrilus iwakiensis sp. nov., is described from Cambaroides japonicus (de Haan, 1849), the endemic freshwater Japanese crayfish, collected in Aomori Prefecture, northern Honshu Island, Japan. The anatomical features used to identify C. iwakiensis are compared with those of its closest congener, C. nipponicus (Yamaguchi, 1932), as well as C. aomorensis (Yamaguchi, 1934) and C. tsugarensis Gelder and Ohtaka, 2000 distributed in the same region.

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Specimens of the echinorhynchid acanthocephalan Acanthocephalus minor Yamaguti, 1935 were collected from the rectum of a dark sleeper, Odontobutis obscura (Temminck and Schlegel, 1845), in an irrigation canal near Lake Biwa, Shiga Prefecture, west-central Japan. This represents a rediscovery of A. minor in the Lake Biwa basin after a gap of nearly 80 years. It appears not to be distributed in Lake Biwa proper, but to occur rarely in rivers and irrigation canals of a limited coastal area around the lake. To date, 10 nominal species of acanthocephalan in four families and three orders have been reported from fish in the Lake Biwa basin. Among these, striking morphological similarities between Acanthocephalus aculeatus Van Cleave, 1931 and its congener A. opsariichthydis Yamaguti, 1935 are noted. It is furthermore suggested that A. gotoi Van Cleave, 1925 could not maintain its population after the basin's wild population of its major host, Anguilla japonica Temminck and Schlegel, 1846, disappeared in the mid-1960s.

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The solitary entoproct Loxosoma axisadversum Konno, 1972 was found on the body surface of the maldanid polychaete Nicomache personata Johnson, 1901 obtained among roots of the seagrass Phyllospadix iwatensis Makino collected at a depth of about 1m in Oshoro Bay, Hokkaido, Japan. The species had previously been known from elsewhere in northern Japan, attached to another maldanid, Nicomache minor Arwidsson, 1907. The morphology of the new material is briefly described with photographs taken in life. A preliminary phylogenetic analysis using concatenated partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene, as well as the nuclear 18S and 28S rRNA genes, placed L. axisadversum as the sister taxon to all the rest of Solitaria included in the analysis, indicating non-monophyly of the genus Loxosoma Keferstein, 1862.

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Heterocotyle chinensis Timofeeva, 1983 (Monogenea: Monocotylidae) is reported from the gills of the whip stingray Dasyatis akajei (Muller and Henle, 1841) in the Seto Inland Sea, Hiroshima Prefecture, Japan, as a new country record. A morphological description and illustrations are provided, along with an emended key to the species of Heterocotyle. The present monogenean most likely has some tolerance for low salinity because one of the two infected fish examined was collected in brackish water.

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The alien monogenean Ligictaluridus pricei (Mueller, 1936), parasitic on the gills of the channel catfish Ictalurus punctatus (Rafinesque, 1818), is described from Lake Kasumigaura, Ibaraki Prefecture, central Honshu, Japan, as a new country record. This monogenean is native to North America and is known as an introduced parasite in Eurasia. As it is not strictly host-specific to ictalurids, native freshwater fishes in Japan have a risk of infection by this monogenean species.

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