シオミズツボワムシの大量培養における増殖停滞の機構に関する研究 [in Japanese] Biological Examinations on Growth Stagnation Mechanism in the Mass-producing Batch Culture of the Rotifer, Brachionus plicatilis [in Japanese]
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植え継ぎ式大量培養における増殖停滞の発生機構を知るために, 培養日数を3, 6, 9および12日とした4個の水槽を用意し, 各培養事例におけるワムシの増殖状況や培養水の水質, また仔虫を個体レベルで飼育したときの生活史パラメータを調べた。各培養事例での日間増殖率は, 培養3日目に比べて培養6, 9日目では大幅に低下し, 培養12日目では負に転じた。また, 初産卵までの時間と以後の産卵間隔も6, 12日目では長くなり, 12日目ではふ化率の低下と仔虫および親虫の死亡も起こっていた。これらの現象が個体群における増殖の停滞を招いていると考察されたが, 溶存態と思われる何らかの阻害物質が, 従来報告のある非解離アンモニアと同様に増殖阻害の原因物質になっていることも示唆された。なお, 増殖阻害要因は, 親虫世代のみならず次の仔虫世代の生活史パラメータにまで影響することが示された。植え継ぎ式培養では, ワムシ類は対数増殖期を過ぎて定常期に収獲されることが多く, その場合, 生理的活性や餌料としての質の低下が避けられないものと考えられた。
The mechanism of growth stagnation is examined in the mass culture of the rotifer in the “batch” mode. Culture tanks are prepared that four phases of batch culture are applied one by one as 3, 6, 9 and 12 days in duration. Carefully designed examinations are executed from three viewpoints of characteristics: (1) population growth; (2) quality of the medium; (3) life-history parameters (time to first spawning, duration of embryonic development, and spawning interval) . The daily growth rate was drastically decreased on the 6th and 9th day contrary to the case on the 3rd day; it turned negative finally on the 12th day. The time required to the first spawning and spawning interval were observed longer on the 6th and 12th day than in the other cases; particularly on the 12th day were also found to occur a considerable decrease of hatchability as well as a higher mortality in both neonate and adult stages. The evidence seems to show that factors given by our investigation have important effects to stagnation in population growth of the rotifer. Some dissolved substance was presumed to be the causative agent, as well as unionized ammonia. Those impediment affected not only on rotifers in the course of culture, but also on life-history parameters of the next generation. In the batch culture, the organism is generally harvested in the stationary growth phase which occurs just after the logarithmic one. This chronological trend may inevitably cause the decline of their own biological activities as well as of their nutritional quality as live food.
- Aquaculture Science
Aquaculture Science 50(2), 197-204, 2002-06-20
Japanese Society for Aquaculture Science