Online ISSN : 2424-1407
Print ISSN : 0918-1989
ISSN-L : 0918-1989
  • 長澤 和也
    2020 年 29 巻 p. 7-17
    発行日: 2020/08/01
    公開日: 2020/09/09
    研究報告書・技術報告書 フリー

    Abstract: The bopyrid isopod Athelges takanoshimensis Ishii, 1914 was originally described in 1914 using specimens from Japan and has since been reported from Far Eastern Russia, Korea, China, Taiwan, Philippines, Singapore, Indonesia, and Papua New Guinea. Japan is located at the northernmost limit of the distribution of the species. This review lists all known host species from these countries and shows all collection localities on maps of Japan and East Asia. Two families of hermit crabs, Paguridae and Diogenidae, serve as hosts for A. takanoshimensis. In subarctic and temperate waters, pagurids are major hosts, but their importance decreases in subtropical waters. Diogenids are infested in subtropical and tropical waters, but the known hosts from the latter waters are only diogenids. Infested hosts are usually found in the intertidal zone but there is a record of the species collected as deep as 508–680 m. Prevalence of infestation is usually less than 10% and differs between host species. The previous work of A. takanoshimensis focused largely on its taxonomy, and we need further research to understand various aspects of the biology (e.g., host utilization, seasonal and annual change in occurrence, growth and reproduction, impact on a host) of the species.

  • 王子 修, 石田 正樹, 村松 大輔, 和田 恵次
    2020 年 29 巻 p. 19-24
    発行日: 2020/08/01
    公開日: 2020/09/09
    研究報告書・技術報告書 フリー

    The cheliped waving frequency (number of waves per min) of individual male Ilyoplax pusilla (Brachyura, Dotillidae) during the reproductive season was investigated in terms of body size, temperature and season at two sites where the density at one site was ca. 3 times higher than that at the other site. The waving frequency in the high-density site was ca. 1.5 times higher than in the low-density site. The males waved more intensely in the middle reproductive season, but the seasonal change in the waving frequency was not strongly related with the air temperature. There was also no clear association between the body size and the waving frequency, which is contrast with the positive association so far known for several ocypodoid species including I. pusilla. Among body size, site (high or low density), temperature and research period, site (i.e. the population density) was the most important factor to predict the waving frequency.