WEKO3
アイテム
有害赤潮ラフィド藻Chattonellaのシストに関する生理生態学的研究
https://fra.repo.nii.ac.jp/records/2003240
https://fra.repo.nii.ac.jp/records/20032401ab6f059-a5bd-4943-9933-98dc8e6481c6
| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-04-25 | |||||
| タイトル | ||||||
| タイトル | 有害赤潮ラフィド藻Chattonellaのシストに関する生理生態学的研究 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | Physiology, Morphology, and Ecology of Cysts of Chattonella (Raphidophyceae), Causative Flagellates of Noxious Red Tides in the Inland Sea of Japan | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
今井, 一郎
× 今井, 一郎 |
|||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | In recent years, many red tide incidents have recurrently occurred in Japanese coastal waters, mainly in the Seto Inland Sea. Amongst these red tide causative organisms, Chattonella antiqua (HADA) ONO and Chattonella marina (SUBRAHMANYAN) HARA et CHIHARA, Raphidophyceae, are known to be fish-killing flagellates which cause severe damage to fish farming (amounts of ¥ billion), especially to yellowtail Seriola quinqueradiata cultures, during the summer season. Information on the life cycle of Chattonella including cyst stage has been limited hitherto, although the information is essential in order to clarify the mechanisms of the red tide occurrences. In this study, morphology, physiology, and ecology of cysts of Chattonella were investigated and the ecological roles of the cysts were discussed concerning overwintering and initiating the summer red tides. It had long been unsuccessful to identify the morphology of the cysts of Chattonella despite many efforts devoted by a number of workers. The cysts of Chattonella were found for the first time from surface sediments of Suo-Nada, western Seto Inland Sea. The cysts were effectively recovered from sediment samples by discontinuous density gradient centrifugation using metrizamide-seawater solution (specific gravity, 1.4). Living cysts of Chattonella were yellowgreenish to brownish in color, and provided with several spots of dark brown or black materials. Most of cysts were found to adhere to solid surfaces such as diatom frustules, sand grains, etc. Clusters of several cysts including empty ones were sometimes observed. The cysts were mostly hemispherical, 25-35 μm in diameter and 15-25 μm in height, and were markedly smaller than common vegetative cells. Discrimination of cysts of the two species was impossible on the basis of their morphological features. Living cysts showed autofluorescence of chloroplasts under blue-light excitation regardless of the germinability. This fluorescence characteristics made it possible for one to enumerate directly the number of cysts in sediment samples by employing epifluorescence microscopy. In both C. antiqua and C. marina, cyst formation was observed in culture under laboratory conditions. Cysts of both species formed in culture displayed morphological characteristics quite similar to those natural cysts observed in sediments collected from the Seto Inland Sea. The combination of factors such as nutrient depletion (nitrogen limitation), adherence to solid surfaces (glass beads), and low light intensities of 1,000 lx or below (or darkness) was essential for cyst formation. In C. marina, germination of cysts was observed under adequate conditions for germination (22°C, 3,500 lx with a 14hL-10hD photo-cycle) after storage at 11°C in the dark for more than four months, although the germination was low incidence. Physiology and ecology of cysts of Chattonella were investigated by the extinction dilution method (MPN method) using natural cysts in sediment samples collected from the Seto Inland Sea. Temperature was a principal factor to induce germination of cysts. Germination of cysts was not found at 10℃, very low at 15 and 18°C, while it increased at 20℃ with maxima at 22 and 25℃, and then decreased markedly at 30℃. Maturation (acquisition of germinability) and dormancy of cysts were significantly affected by temperature. For maturation of cysts, low storage temperature of 11°C or below for more than four months were needed whereas no maturation was observed at 20°C or more. Temperatures of 15 and 18℃ were critical for maturation. Matured cysts in sediments maintained the germinability at the storage temperature of 11°C or below. They lost the germinability gradually at 15 and 18℃ during storage, and did rapidly at 20℃ or more. In fresh sediments of Suo-Nada, marked seasonality of germinability was confirmed in the cysts of Chattonella. It was weak from autumn to early winter, then strengthened gradually up to a high level, which was maintained between spring and early summer, and again decreased rapidly during summer. The annual life cycle of Chattonella, including vegetative and dormant phases, was summarized as follows: (1) vegetative cells in early summer originated from the germination of cysts in sediments; (2) they form cysts during the summer season; (3) the cysts spend a period of spontaneous dormancy until next spring; (4) the duration of post dormancy, an enforced dormancy due to low temperatures, follows until early summer. The cyst populations which missed a chance of germination during summer could be carried over to the next year through secondary dormancy in sediments. The life cycle of Chattonella is therefore well adapted to the temperature regime in temperate seas such as the Seto Inland Sea. In Suo-Nada, distribution of cysts in sediments and occurrence of vegetative cells during summer were investigated together with environmental factors such as surface and bottom water temperatures. Densities of cysts ranged from 0 to 787·cm-3 wet sediment in March 1986, and from 0 to 490·cm-3 in June 1987. Cysts were abundant in the central area, whereas scarce in the western coastal area, in both years. From the results of field observations in Suo-Nada, it was suggested that the cysts started to germinate from coastal shallow area where bottom water temperature was relatively higher than deeper area and reached the optimum level (ca. 20℃) for germination in early June. Since bottom water temperature rises gradually from coastal shallow area to deeper area, the germination of cysts presumably continue for rather long period. Long period germination is considered to be superior seeding strategy for Chattonella red tides, because Chattonella can take more chances for population developments during summer season. Distribution of cysts of Chattonella in sediments were investigated by extinction dilution method and direct count technique in the Seto Inland Sea such as Osaka Bay, Harima-Nada, Bingo- and Hiuchi-Nada, northern Hiroshima Bay, and Suo-Nada, and Kagoshima Bay in southern Kyushu. High density parts were observed in each area. Mean densities of cysts were generally in order of 102.cm-3 in sediments of the above areas except for northern Hiroshima Bay where cysts were scarce (<5 cysts . cm-3). From the results of this study, it was confirmed that the cysts of Chattonella play an important role in initiating red tides in the summer through capability of overwintering in bottom sediments. It is therefore suggested that monitoring of the rise of bottom water temperature at shallow station in dense seed bed from spring to summer is useful in predicting the appearance of the vegetative populations in the early stage of the red tide. | |||||
| 言語 | en | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 瀬戸内海を中心とする西日本沿岸域は,ハマチやマダイ等を対象とする養殖漁業の盛んな水域であるが,1969年以降 Chattonella (C.antiqua とC.marina)による赤潮が夏季に頻発し,養殖魚類の大量斃死を引き起こして数十億円規模の大被害を与えることも多く,社会問題となっている。Chattonella においてはシストの時期を含む生活史がこれまで全く不明であり,赤潮の発生機構を理解する上で,その解明が永く待たれていた。本研究は,Chattonella の越冬形態であるシストの形態を明らかにし,赤潮発生における seed population としてのシストの生態的役割について検討した結果を取りまとめたもので,その主な内容は次の通りである。Chattonella のシストは形態が不明であったが,探索法を工夫することによって海底泥中のシストを初めて発見し,その形態を明らかにした。シストは黄緑色~茶色を呈し,砂粒や珪藻の被設等に付着しているものが多く,単独あるいは数個の塊状で存在した。シストの背面観は径約25-35μm の円ないし楕円形,側面観は高さ約15-25μmの概ね半円形をしていた。形態的特徴に基づく限り,重要種である C.marina とC.antiqua のシストの識別は不可能であった。青色励起光によって葉緑体起源の赤色自家蛍光をシストが発することが判明し,これによって海底泥中のシストを直接計数する技法を確立した。培養条件下で C. antiqua とC.marina のシストの形成に成功した。シストの形成条件として窒素源欠乏,付着基質の存在,約1,000 lx以下の低照度の組み合わせが有効であることが明らかとなった。シストの休眠や成熟(発芽能力の獲得)に及はす温度の影響と,現場水域(周防灘)の海底泥中のシストの発芽の季節性を検討した。秋の時点で海底泥中の殆どのシストは休眠状態であったが,海底泥試料を20℃以上に置くとシストは殆ど成熟せず,15-18℃は臨界的であり,11℃以下で休眠が解除されて成熟した。現場海底泥中のシストは,発芽に関して著しい季節性を示した。1月には発芽可能なシストは少ないが,4月になると著しく増加し,7月中旬頃までそれが維持され,8月中に急速に発芽しなくなった。以上から,シストは秋~冬にかけて自発的休眠を行い,その休眠の解除には4ヶ月以上の冬の低温期間が必要であることが明らかとなった。また,シストの発芽には温度が大きく影響し,10℃以下では発芽せず,15と18℃で少数が発芽し,20℃で発芽が活発になり,22と25℃がその最適温度であり,30℃で再度減少することが判明した。さらに,夏季の間に埋まり込み等で発芽の機会を逸したシストは二次休眠を行い,翌年の夏へと持ち越されることが明らかとなった。周防灘を対象水域として現場調査を実施し,シストの分布,夏季のシストの挙動と栄養細胞の出現状況,および環境要因(特に温度)の変化を調べた。シストは1986年3月で0-787個·cm 3(湿泥),1987年6月で0-490個·cm-3の密度で存在した。現場調査の結果から,周防灘におけるシストの発芽は水深の浅い沿岸域を始まりとして6月頃から起こり,順次水深の大きい沖合域へと発芽する場所を拡大して行き,灘全体としてはかなり長期間シストの発芽が継続していると推定された。瀬戸内海の諸水域(大阪湾,播磨灘,燧·備後灘,広島湾北部)および鹿児島湾の海底泥中のChattonella のシストの分布密度を調べた。広島湾北部では殆どシストが検出されなかったが,他の水域では平均的に102個·cm-3(湿泥)のオーダーでシストが存在している事実を明らかにした。 | |||||
| 言語 | ja | |||||
| bibliographic_information |
ja : 南西海区水産研究所研究報告 en : Bulletin of Nansei National Fisheries Research Instituite 巻 23, p. 63-166, ページ数 104, 発行日 1990-03 |
|||||
| 出版者 | ||||||
| 出版者 | 南西海区水産研究所 | |||||
| 言語 | ja | |||||
| 出版者 | ||||||
| 出版者 | Nansei National Fisheries Research Instituite | |||||
| 言語 | en | |||||
| item_10002_source_id_9 | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 0388-841X | |||||
| item_10002_source_id_11 | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00181988 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | nnf_k_23_63 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010460896 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本農学文献記事索引(agriknowledge) | |||||
