Two new poecilostomatoid copepod species, Kelleria japonica n. sp. and K. pararegalis n. sp., belonging to the family Kelleriidae are described from an eelgrass bed on the southwest coast of Shikoku Island, western Japan. The family is new to the fauna of Japan. Kelleria japonica is similar to four congeners by having a bilobed medial process on the female leg 5, but distinguished from them by a combination of features in some of the following appendages, the caudal ramus and the terminal spines of the maxilla in both female and male, the female leg 5, and the male legs 1 and 2. Kelleria pararegalis is most similar to K. regalis, described from the Suez Canal, but differs from the latter in the body length in both female and male, the medial process on the first segment of the maxilliped and the inner apical spine of leg 5 in the female, and the outer apical spine of the leg 2 endopod in the male.

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Basal experiments that examine the impact of hypoxia on bivalves provide an explanation for dominant bivalve population maintenance in hypoxic soft-bottom habitats. We conducted laboratory experiments to assess the effect of persistent anoxia on the survival of three bivalve species: Manila clams (Ruditapes philippinarum), ark shells (Anadara kagoshimensis), and Veremolpa micra. Further, we compared the interspecific variation of ark shells among different habitats in the intertidal and subtidal regions of Ariake Bay and Lake Nakaumi, Japan. A marked inter- and intraspecific variation was detected with respect to survival under anoxic conditions. Specifically, the survival of V. micra and ark shells in Lake Nakaumi under persistent anoxia was significantly higher than that of ark shells in Ariake Bay and Manila clams in Tokyo Bay. Further experiments indicated that ark shell survival (LT₅₀) under persistent anoxia with sulfurization was significantly lower than that under anoxia alone. Such inter- and intraspecific variations in anoxia and sulfurization tolerance might reflect the dominance of certain bivalve species in hypoxic regions.

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The cucumariid sea cucumber Plesiocolochirus inornatus (Marenzeller, 1881) was rediscovered in shallow water of the Pacific Ocean, on the south coast of Fukushima Prefecture, eastern Japan. The last report of this species in Japanese waters was published a hundred years ago, although this species possibly has a wide distribution in Japanese waters. Since there is no detailed information on its external appearance, we prepared images of the body shape on the basis of six new specimens. The body of P. inornatus has obviously distinguishable dorsal and ventral sides in the living state with tapered ends that turn upwards, mid-body of the ventral side extremely flattened and nearly half-round in cross-section, dorsal surface smooth with retracted minute ambulacral-papillae scattered uniformly regardless of radii or inter-radii. Furthermore, detailed images of ossicle shape and calcareous ring shape were prepared.

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We described a cryptic population of the Portuguese oyster Crassostrea angulata (Lamarck, 1819) identified from the coast of Shikoku Island, Japan. At the same location, we also confirmed the distribution of a recently recognized oyster species, C. dianbaiensis Xia, Wu, Xiao & Yu, 2014. As a diagnostic tool for species identification, we used the nucleotide sequences of three mitochondrial genes. These sequences were capable of reliably discriminating each of the above two species from their most closely related species: C. angulata from C. gigas (Thunberg, 1793), and C. dianbaiensis from C. bilineata (Röding, 1798). Our finding of a previously unrecognized distribution of these species provides important information to help promote the conservation of species diversity of Japanese oysters.

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As part of an ongoing monitoring study of phytoplankton in Yemeni coastal waters we report, for the first time, a dense bloom (14.3×10⁶ cell L⁻¹) of the marine dinoflagellate species Protoperidinium quinquecorne (Abé) Balech on June 6, 2012 from the coastal water of Al Hodeidah and Khor Al-Khateeb lagoon, southern Red Sea. Water temperature was 34°C and salinity was 36 during the bloom, indicating its tropical and subtropical nature. This bloom was accompanied by a massive kill of small pelagic fish, which were mostly sardines. Among the phytoplankton species reported during the P. quinquecorne bloom, the red tide-forming species, Trichodesmium erythraeum (cyanobacteria), Gonyaulax verior, and Prorocentrum micans, and the known toxic species, Dinophysis acuminata, were notable.

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