著者

武田 真城 池田 実

出版者

アクオス研究所

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.2022, pp.1-20, 2022 (Released:2022-02-14)

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The freshwater shrimp Palaemon paucidens C type is likely to be endemic to Amami-Oshima Island. We investigated the distribution of the shrimp in 34 rivers on Amami-Oshima and Kakeroma Islands, and implemented DNA analysis and rearing experiment for the seawater requirement of the larvae. This type was found only in Katoku River in the southeastern part of Amami-Oshima Island. Mitochondrial (16S rDNA) and nuclear (18S rDNA) DNA analyses revealed substantial sequence differences between the C type and other two types (A and B) collected from the Japanese Archipelago. This result strongly indicates that the C type is a unique group that is geographically isolated and has diverged genetically from the two types in the Japanese Archipelago. The zoeal larvae of C type showed higher survival rate in 30 % and 70 % seawater than 0 % or 100 %, suggesting that this type has amphidromous life history as the B type. Considering the limited distribution and low genetic diversity of the C type, the risk of extinction is probably high. For the viability of this type, conservation of the landscape of Katoku River, including its estuary, is needed.