著者

伊藤 寿茂 神応 義夫

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.33, pp.5-14, 2020 (Released:2020-12-28)

参考文献数

17

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Labroides dimidiatus is a well-known species of cleaner fish, while there are not many observation records on cleaning behavior of Plotosus japonicus. In this study, cleaning behavior of P. japonicus and L. dimidiatus was observed in a large aquarium tank (approximately 1000 m3 in capacity) at the Enoshima Aquarium to examine the relationship between their cleaning behavior and client fishes’ requesting behavior. P. japonicus was observed to perform cleaning behavior on 32 client species, some of which (17 species) displayed requesting behavior to P. japonicus. A total of 53 client species were recorded for L. dimidiatus, many of which (26 species) displayed requesting behavior to L. dimidiatus. We confirmed that in addition to L. dimidiatus, P. japonicus and some client species also developed their relationship through symbiotic coactions.

著者

梶原 冴月 山内 健生

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.36, pp.15-17, 2023-12-07 (Released:2023-12-07)

参考文献数

8

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Larval transport by adult Lasius morisitai was observed in nests of L. morisitai in a single tree of Abies sachalinensis in Obihiro, Hokkaido, Japan. Larval transport was observed on 21 June and from 29 September to 7 October 2022 during the day (8:00-11:00am and around 3:30pm), just after sunset (around 5:00pm), and at night (8:00-10:00pm).

著者

上出 櫻子 清水 彩美 小井土 美香 信田 真由美 小南 優 吉澤 茜 小山 理恵 早川 洋一 小林 牧人

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.29, pp.31-39, 2016 (Released:2020-01-12)

参考文献数

12

被引用文献数

2

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The Japanese medaka is designated as an endangered species because of its decreasing population, and conservation of the medaka is an urgent concern. In the present study, in order to obtain basic information for conservation of wild medaka, we observed the reproductive behavior of female medaka (Oryzias latipes, orange-red variety and wild fish) in experimental aquaria under various environmental conditions. Female medaka normally deposited eggs on aquatic plants or aquatic mosses which were solid with a soft surface in experimental aquaria. However, the fish did not deposit eggs but discarded eggs in aquaria provided with sand, floating aquatic plants, and no substrate, and in an aquarium lined with concrete. These results indicate that a suitable substrate is essential for successful egg deposition of medaka, and suggest that maintaining suitable vegetation in natural environments is important for conservation of wild medaka.

著者

小林 牧人 黑栁 仁志 大友 明香 早川 洋一

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.32, pp.7-13, 2019 (Released:2020-01-07)

参考文献数

18

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Construction of artificial river and lake banks changes the aquatic environment, and these changes are known to cause decreases of aquatic plants in shallow waters. We conducted experiments to examine the involvement of aquatic plants in spawning behavior of goldfish, Carassius auratus, and cruicuan carp, Carassius buergeri subsp.2. The spawning behavior was induced by injecting prostaglandin F2α into females. Pairs of male and female goldfish or crucian carp were placed in experimental tanks with or without aquatic plants made of acrylic yarn. Both goldfish and crucian carp spawned actively onto the aquatic plants whereas the behavior significantly decreased without the aquatic plants. The present experiments demonstrate that aquatic plants are essential as spawning substrates for performance of spawning behavior of these species. It is critical for conservation of fish species that use aquatic plants as spawning substrates to maintain aquatic plants on river and lake banks.

著者

上出 櫻子 木村 恵美 小林 牧人

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.33, pp.1-4, 2020 (Released:2020-12-28)

参考文献数

11

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Japanese medaka (Oryzias latipes) is known to deposit fertilized eggs on aquatic substrates in shallow waters. In order to examine the influence of water depth on embryonic development of fertilized eggs of an orange-red variety and wild medaka, we observed fertilized eggs for 18 days and compared the hatching rate and the hatching time at different water depths of 5, 30, and 65 cm. The hatching rate was lower at 65 cm depth than at 5 cm depth and the hatching time was longer at 65 cm depth than at 5 cm depth with both the orangered variety and the wild medaka. These results indicate that deep water is not suitable for the embryonic development of medaka and suggest that preservation of natural conditions in shallow waters of rivers and ponds is important for conservation of wild Japanese medaka.

著者

上出 櫻子 小南 優 小林 牧人

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.30, pp.1-4, 2017 (Released:2020-01-07)

参考文献数

12

被引用文献数

1

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The present study examined the preference in water depth for egg deposition of female, orangered variety medaka Oryzias latipes in order to obtain basic information for conservation of wild medaka. Substrates for egg deposition were set at various depths in experimental aquaria and male and female medaka were kept in the aquaria for seven days to observe spawning. The number of eggs and the egg deposition depth were recorded every day. The female medaka deposited eggs on the substrates at various depths but notably a significantly large number of eggs were deposited at shallow depths. These results indicate that female medaka gives a preference to shallow water depths for egg deposition.

著者

片山 敦 佐藤 僚介 吉川 朋子

出版者

公益財団法人 平岡環境科学研究所

雑誌

自然環境科学研究 (ISSN:09167595)

巻号頁・発行日

vol.30, pp.5-12, 2017 (Released:2020-01-07)

参考文献数

34

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外来のカワリヌマエビ属の河川や池での生息の報告が,近年関東でも多くされており,在来のヌカエビへの影響が懸念されている.本研究では両種の生息が確認されている鶴見川水系において,分布調査を2014 年および2016–2017 年に行った.2014 年の調査では,カワリヌマエビ属は河川のほぼ全域に出現し,2 地点のみでヌカエビが同所的に採取されたが,2016年にはカワリヌマエビ属のみで,ヌカエビは確認されなかった.池については2014 年には1 地点でカワリヌマエビ属とヌカエビが同所的に,3 地点でヌカエビのみが出現したが,2017 年には2 地点はカワリヌマエビ属のみに置き換わり,ヌカエビのみが生息しているのは2 地点だけであった.この調査でカワリヌマエビ属が侵入すると個体数がほぼ同数の状態から2–3年でカワリヌマエビ属に置き換わることが明らかになった.今後はヌカエビが生息する池への人為的な移入を防ぐために,外来カワリヌマエビ属の問題について,普及啓発を行っていくことが重要だと考えられた.