著者

Fujimoto Takafumi Fujimoto Suzu Murakami Masaru Yamaha Etsuro Arai Katsutoshi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.103-111, 2020-08-24

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Tetraploid strains are important sources of diploid gametes available for further expansion of ploidy manipulation. Although artificial induction of tetraploid strains has been attempted by inhibition of a mitotic cell division of zygotes using hydrostatic pressure or temperature treatments at the early developmental stage, successful examples of viable and fertile tetraploid fish were very rare. Because most resultant tetraploid progeny exhibited extremely high mortality. Natural tetraploid variants are considered another source of diploid gametes. In the present study, we tried to induce new strains of tetraploid, triploid and androgenetic diploid using diploid sperm of a tetraploid ginbuna (Japanese silver crucian carp Carassius auratus langsdorfii), which caught at the Jounuma lake, Gunma Prefecture, Japan. New tetraploids, i.e., neo-tetraploids were induced by fertilizing eggs of a diploid goldfish Carassius auratus auratus with diploid sperm of the tetraploid ginbuna, followed by heatshock (40°C for 45, 60 and 75 s) to inhibit the second polar body release at 5 min after fertilization. Although a small number of neo-tetraploid fish survived, we could not obtain any fertile gametes from them in the present study. Triploids were successfully induced by fertilizing eggs of a diploid goldfish with diploid sperm of the tetraploid ginbuna. Some resultant triploid males produced aneuploid sperm at the age of maturation. Androgenetic diploids were induced by fertilizing UV-irradiated eggs of diploid goldfish with diploid sperm of the tetraploid ginbuna. A mature androgenetic diploid produced fertile haploid sperm.

著者

Fujioka Kantaro Kinoshita Masataka Choi Jai-Ho Fuse Keisuke Gamo Toshitaka Hasumoto Kouji Ishibashi Jun-ichiro Koga Kazuhide Miyata Hiroki Nishiyama Ei-ichiro Sayanagi Keizo Shimamura Kiyoshi Shitashima Kiminori Suzu

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.62, no.2, pp.61-132, 1987-10-23

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The Mikura Basin and Hachijo Basin lie just beyond the volcanic front of the Izu-Ogasawara arc-trench system and the existence of submarine hydrothermal activity is expected. This area was surveyed during the cruise of KT 86-10 by the R/V Tansei-Maru, Ocean Research Institute, University of Tokyo from the 12th to the 21st of July, 1986. A small topographic high west of the Inanbajima which occupies the central part of the basin was found by a 12 kHz echo sounder as well as a seismic profiler. The small topographic high consists mostly of the boulder of volcanic rocks which were recognized later as two pyroxene andesites by the submersible "Shinkai 2000" of JAMSTEC. The other parts of the basins are covered by thick volcanogenic and biogenic materials having bioturbation structures on the surface by the bottom dwelling organisms. The geologic developments of the basins viewed from the present observations are as follows: Basement of the region was cut by the normal faults relating to the initiation of rifting the northern Izu-Ogasawara backarc area and followed to subside. Thick volcanic materials covered the basement. Compressional stress field after the end of the rifting may take place to form folding and fissure eruption of andesitic lava to make small knoll. CTD (Conductivity, Temperature, Depth) measurements across the knoll were carried out and temperature anomalies were found near the knoll. The temperature and salinity relationship observed along the knoll gives negative possibility to support the existence of presentday hydrothermal activity. Multichannel seismic profiler data show the existence of a low velocity part, which may possibly be a magma chamber, about 1.5 km beneath the Mikura Basin. All the other data support the existence of hydrothermal activity in the basins. However, it will be necessary to have more elaborate surveys of this area in future studies.御蔵海盆と八丈海盆は伊豆.小笠原島弧-海溝系の火山フロントのすぐ背後に位置している.これらの海盆には海底熱水活動の存在が期待されている.東京大学海洋研究所の淡青丸によるKT86-10次航海が1986年7月12日から21日の間行われ,この地域の地質学,地球物理学,及び地球化学的な調査がなされた.御蔵海盆の中央にある藺灘波島の西部からPDRと音波探査によって小さな地形的高まりが発見された.この高まりは北北西-南南東の伸長方向を持ちその幅数100メートル,高さ数10メートルで2マイル程度連続する.これは,火山岩の巨礫の積み重なった小丘で,その深部には断層が発達している.この火山岩の大部分は両輝石安山岩であることが後の「しんかい2000」の潜水調査で確かめられた.周辺の海盆底は厚い火山源及び生物源物質によって埋立てられており,堆積物が底生生物によって著しく乱されている.これらの海盆の発達史は音波探査の記録から以下の通りまとめられる.まず伊豆・小笠原背弧のリフティングに関連した正断層群によって,この地域の基盤が切られ沈降した.ひきつづきこの基盤を厚い火山物質が覆った.次に,北北西-南南東方向のσhmaxに平行な安山岩質溶岩の広域割れ目噴火を起こし,活断層と伴に小丘が形成され,この小丘を横切ってCTDの観測が行われ小丘の近くで0.05℃程の温度異常が見つかった.小丘に沿って観測された温度と塩分濃度の関係は現在の熱水活動の存在に否定的である.しかし,マルチチャソネル音波探査の結果は御蔵海盆の深さ約1.5kmのところにマグマ溜りの存在を示している.島弧を横切る方向の地殻熱流量の値の分布が火山フロントで高く,背にでもやや高いこと,断層による陥没及び活断層の存在,深海カメラや潜水艇で熱水性堆積物らしいものが撮影されていること,潜水艇のマニピュレータで得られた安山岩にFe-Mnに富む堆積物が付着していたことなどは海盆に熱水活動の存在することを支持しているが,この海域のもっと丹精なる調査が将来必要である.