Now showing items 1-2 of 2

    • Article

      The first record of a cupped oyster species Crassostrea dianbaiensis in the waters of Japan 

      M Sekino, H Ishikawa, A Fujiwara, EFC Doyola-Solis, MJH Lebata-Ramos & H Yamashita - Fisheries Science, 2015 - Springer Verlag
      With a combination of our mitochondrial and nuclear DNA data, we evidenced the occurrence of a Crassostrea oyster hitherto unrecognized in Japan. This species, C. dianbaiensis (named Sumizome-gaki in Japanese), was very recently described as a new “tropical” oyster, although we located it in a temperate water zone (southwestern coast of Shikoku Island, Japan). Our specimens bore a morphological resemblance to the slipper cupped oyster C. bilineata (syn. C. iredalei), consistent with their close phylogenetic relationship. Some of the shell characteristics represented in the original species description were not applicable to our specimens, especially in terms of the pattern of their inner-shell coloration. Our novel finding of C. dianbaiensis in Japan updated the taxon list of Japanese Crassostrea species.
    • Article

      Full-genome sequencing and confirmation of the causative agent of erythrocytic inclusion body syndrome in coho salmon identifies a new type of piscine orthoreovirus 

      Erythrocytic inclusion body syndrome (EIBS) causes mass mortality in farmed salmonid fish, including the coho salmon, Onchorhynchus kisutchi, and chinook salmon, O. tshawytscha. The causative agent of the disease is a virus with an icosahedral virion structure, but this virus has not been characterized at the molecular level. In this study, we sequenced the genome of a virus purified from EIBS-affected coho salmon. The virus has 10 dsRNA genomic segments (L1, L2, L3, M1, M2, M3, S1, S2, S3, and S4), which closely resembles the genomic organization of piscine orthoreovirus (PRV), the causative agent of heart and skeletal inflammation (HSMI) in Atlantic salmon and HSMI-like disease in coho salmon. The genomic segments of the novel virus contain at least 10 open reading frames (ORFs): lambda 1 (λ1), λ2, λ3, mu 1 (μ1), μ2, μNS, sigma 1 (σ1), σ2, σ3, and σNS. An additional ORF encoding a 12.6-kDa protein (homologue of PRV p13) occurs in the same genomic segment as σ3. Phylogenetic analyses based on S1 and λ3 suggest that this novel virus is closely related to PRV, but distinctly different. Therefore, we designated the new virus ‘piscine orthoreovirus 2’ (PRV-2). Reverse transcription–quantitative real-time PCR revealed a significant increase in PRV-2 RNA in fish blood after the artificial infection of EIBS-naïve fish but not in that of fish that had recovered from EIBS. The degree of anemia in each fish increased as the PRV-2 RNA increased during an epizootic season of EIBS on an inland coho salmon farm. These results indicate that PRV-2 is the probable causative agent of EIBS in coho salmon, and that the host acquires immunity to reinfection with this virus. Further research is required to determine the host range of PRV species and the relationship between EIBS and HSMI in salmonid fish.