著者

Keiichi Kakui Tomoyuki Komai

出版者

Aquos Institute

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.2022, pp.AA2022-1, 2022 (Released:2022-01-30)

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We report the first occurrence record of the freshwater ectoparasitic platyhelminth Scutariella japonica (Matjašič, 1990) from Hokkaido, Japan. The flatworms were collected from the surface of exoskeleton and the inside of branchial chamber of the atyid shrimp Neocaridina sp. aff. davidi. Phylogenetic analysis based on the 18S + 28S concatenated dataset of rhabdocoel flatworms retrieved the Scutariella clade, and our specimens identified with Scutariella japonica were genetically distinct from those referred to S. sinensis Chen, Feng, Lin, Lu & Wang, 2018. Phylogenetic analyses using COI showed that the host shrimp specimens from Sapporo were clustered with N. koreana identified by Shih et al. (2017) and placed close to N. palmata (Shen, 1948) and N. davidi (Bouvier, 1904). Our specimens did not agree with the original description of N. koreana Kubo, 1938, particularly in the shape of the endopod of the male pleopod 1. The identity of the present host shrimp specimens could not be established satisfactorily, and thus they were referred to N. sp. aff. davidi for the time being.

著者

張 成年 柳本 卓 松崎浩二 小藤一弥 星野浩一

出版者

Aquos Institute

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.AA2019, pp.AA2019-5, 2019 (Released:2019-09-30)

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チゴダラとエゾイソアイナメ間には顕著な形態差がなく同種の可能性が指摘されてきたものの本邦ではこれらを別種として扱ってきた。その根拠として、前者は東京湾以南の深海(150‒650m)に分布し、眼径が大きく体色が淡褐色であること、後者は函館以南の浅海(数10m以浅)に分布し、眼径が小さく体色が濃褐色であること、が挙げられている。本研究では北海道から神奈川県の範囲で44個体のチゴダラ類標本を採集し、上記の表現型とともにミトコンドリアDNAの3領域(COI、16S rDNA、Dloop)の塩基配列を分析した。体色は個体間変異が大きいものの浅場標本(80m以浅)では濃褐色個体が多く、深場標本(200m以深)では淡褐色個体が多かった。眼径/吻長も個体間変異が大きく深場標本と浅場標本の平均値間に有意差はなかった。個体間および浅深標本間の遺伝的差異は非常に小さく種内個体間レベルの範囲であることが示された。データベースより入手したチゴダラ属他種の配列を加えた系統樹解析においても、本研究で分析した個体は全て独立したクレードに属し同種と考えられた。以上のことからチゴダラとエゾイソアイナメは同種であり、体色や眼径の変異は種内個体間差であることが示された。

著者

Yoshihiro Akiyama Tomonari Okada Takeshi Yuhara

出版者

Aquos Institute

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.2022, pp.AA2022-13, 2022-07-04 (Released:2022-07-04)

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We report the presence of mobile macro-epifauna on rafts of pumice generated by the Fukutoku-Oka-no-Ba volcano in 2021 in Oku Port, at the northern end of Okinawa Island. Most of the water surface in the harbor was covered by a thick pumice raft at the time of our observations. Grapsus crabs were the dominant species on the surface of the raft, and many crabs were visible near the quay. No crab was seen to burrow into the raft. These results show that mobile macro-epifauna can expand their distribution to the surface of a pumice raft. However, the presence of a raft is likely to make it difficult for crabs to move between land and water.

著者

Daiichi Ogano Shawichi Kagayama

出版者

Aquos Institute

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.2023, pp.AA2023-8, 2023-05-01 (Released:2023-05-01)

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The Japanese pond turtle (Mauremys japonica) is endemic to Japan, inhabiting Honshu, Shikoku, Kyushu, and smaller islands. The ecology and distribution of M. japonica have been well studied in western Japan. In contrast, much less studies of this species have been performed in the Kanto and Hokuriku regions and its northern limit is not clear. Here, we report the discovery of a local population of M. japonica in a river in the Ibaraki Prefecture, representing the northern limit of its range on the Pacific Ocean side of Japan. This investigation revealed the inhabitation of over 50 turtles aged 0–10 years in the river. The predicted growth curves of both male and female turtles were comparable to those in other river and wetland populations previously reported, indicating that this population reproducing and growing normally. We also discuss future conservation strategies for this population.

著者

Yoshinobu Hayakawa Keiichi Kakui

出版者

Aquos Institute

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.2022, pp.AA2022-10, 2022-06-09 (Released:2022-06-09)

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We report microhabitats used by the tanaidid tanaidacean Zeuxo ezoensis Okamoto et al., 2020 on the marine alga Sargassum confusum C. Agardh, as well as its molting behavior, based on observation of captive individuals. Zeuxo ezoensis constructed its tube-shaped nests on S. confusum (1) at the bases of lateral branches, (2) on main branches in the apical region, (3) in cracked air bladders, and (4) in clumps of a filamentous alga (Chordariaceae sp.) epiphytic on S. confusum. The behavioral sequence of a single molt observed for a male Z. ezoensis was as follows. (1) A break occurred along the ventrolateral and posterodorsal edges of the carapace, creating a dorsal opening in the old exoskeleton; (2) the animal began to extricate itself from the old exoskeleton through this opening; (3) the cephalothorax and its appendages shed the old exoskeleton; and (4) the animal completed extrication from the old exoskeleton. The entire molt took about five minutes.

著者

張 成年 柳本 卓 小西光一 Charles H. J. M. Fransen

出版者

Aquos Institute

雑誌

水生動物 (ISSN:24348643)

巻号頁・発行日

vol.AA2019, pp.AA2019-7, 2019 (Released:2019-09-30)

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スジエビ(Palaemon paucidens De Haan, 1844)には遺伝的に異なる3タイプ(A、B、C)が発見されていることから複合種であると考えられる。2世紀近く前にシーボルトが採取しオランダの国立民族学博物館に収蔵されているタイプ標本の16S rDNAを分析したところ、AタイプのうちJA1ハプロタイプであることがわかった。JA1タイプは日本中部から南部にかけて最も多く出現するタイプであり、長崎周辺に限られていたシーボルトの活動範囲とも符合する。