Online ISSN : 2424-1407
Print ISSN : 0918-1989
ISSN-L : 0918-1989
  • 丸山 智朗, 岡本 研
    2022 年 31 巻 p. 5-18
    発行日: 2022/08/01
    公開日: 2022/08/24
    研究報告書・技術報告書 フリー

    Monthly quantitative sampling of caridean shrimps and prawns, and logging of river water temperatures were undertaken over 13 months in the Kawazu-yatsu and Ogamo Rivers, Izu Peninsula, and the Morito and Shimoyama Rivers, Miura Peninsula, Japan in order to clarify the overwintering status. Low water temperature tolerances of 9 major species were also examined using culture experiments. Water temperatures in the Kawazu-yatsu River were highest throughout the year due to the inflow of hot spring water. Fifteen shrimp and prawn species were collected, the number of individuals tending to decrease in winter in most. In particular, two species, Macrobrachium australe and M.lar, which have low tolerance to low water temperature were found only in autumn in three rivers except Kawazu-Yatsu River, and it was confirmed that they died due to low water temperature in winter. The rate of decline from autumn to winter for the species established in the study area was the lowest in Paratya compressa, which has the highest tolerance to low water temperatures, and in the Kawazu-Yatsu River, which has the highest water temperatures. The decrease in the populations of M. formosense, M japonicum, Caridina leucosticta and C. typus occurred earlier than the decline in river water temperatures, suggesting that they moved to places where it is difficult to collect them, such as deep pools.

  • 佐藤 大義, 饗場 空璃
    2022 年 31 巻 p. 19-28
    発行日: 2022/08/01
    公開日: 2022/08/24
    研究報告書・技術報告書 フリー

    Four decapod crustaceans, Heterocarpus fascirostratus Yang, Chan & Kumar, 2018 (Caridea: Pandalidae), Uroptychus imparilis Baba, 2018 (Anomura: Chirostylidae), Munidopsis similior Baba, 1988 (Anomura: Munidopsidae) and Euryxanthops flexidentatus Garth & Kim, 1983 (Brachyura: Xanthidae) are reported on the basis of specimens collected from the Sea of Hyuga, Kyushu, western Japan, by local off shore commercial trawlers. Munidopsis similior and E. flexidentatus are recorded for the first time from Japan. Images showing living coloration are given for each species. Detailed descriptions and supplemental illustrations are provided for M. similior and E. flexidentatus to show evidence of identification.

  • 藤田 大樹
    2022 年 31 巻 p. 29-36
    発行日: 2022/08/01
    公開日: 2022/08/24
    研究報告書・技術報告書 フリー

    Species in Cymothoidae (Crustacea: Isopoda) are cosmopolitan parasite infesting marine, freshwater and brackish water fishes. In Cymothoidae, Anilocra and Nerocila species have an elongated juvenile stage called the aegathoid stage. A total of 831 Japanese halfbeaks Hyporhamphus sajori (Beloniformes: Hemiramphidae) were collected from 11 sites in Japan. The aegathoid stage was seen infesting a Japanese halfbeak collected from Osaki-Shimojima Island, Kure City, Hiroshima Prefecture, and identified as Anilocra clupei by DNA barcoding using the COI and 16S rRNA sequences. The morphology of this individual was also almost identical to the aegathoid stage of A. clupei in the previous study. The prevalence of the aegathoid stage of A. clupei on Japanese halfbeaks was very low at 0.12% in all of Japan and 0.93% in the coast of Osaki-Shimojima Island. Aegathoid stages of A. clupei may have lower host-specificity than adult females, and be able to infest more comprehensive species of fish, which may increase the survivability of the aegathoid stages.