1990 Fiscal Year Final Research Report Summary
Mechanism of Fish Metamorphosis and its Adaptive Role for Survival.
| Project/Area Number |
63480067
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
General fisheries
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| Research Institution | The University of Tokyo |
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Principal Investigator |
OKIYAMA Muneo Ocean Research Institute, University of Tokyo ; Professor, 海洋研究所, 教授 (00111584)
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| Co-Investigator(Kenkyū-buntansha) |
SOMIYA Hiroaki Faculty of Veterinary Science, Azabu University ; Associate Professor, 獣医学部, 助教授 (50147972)
SARUWATARI Toshiro Ocean Research Institute, University of Tokyo ; Research Associate, 海洋研究所, 助手 (00215899)
OHTAKE Tsuguo Ocean Research Institute, University of Tokyo ; Research Associate, 海洋研究所, 助手 (20160525)
TSUKAMOTO Katsumi Ocean Research Institute, University of Tokyo ; Associate professor, 海洋研究所, 助教授 (10090474)
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| Project Period (FY) |
1988 – 1989
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| Keywords | metamorphosis / direct development / indirect developmemt / leptocephalus / bathylagid fish / ox-eye tarpon / sand fish / developmental stages |
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| Research Abstract |
Fish metamorphosis and its adaptive role for survival was studied on various marine fishes such as ox-eye tarpon of Megalopidae, deep-sea smelts of Argentinoidei, sand fish of Trichodontidae, and flatfishes of Pleuronectidae among others. Our results strongly supported Youson's concept of the first metamorphosis associated with termination of the larval stage as the significant developmental phase critical to the survival strategy.
Contrasting style of early life histories between two species of sandfishes provided a good example in discussing the divergence mechanism of direct and indirect divelopmental patterns, namely, the origin of metamorphosis. Importance of the environmental conditions, particularly annual temperature regime was emphasized in this case. Among the deep-sea smelts including direct and indirect types of development, Bathylagus ochotensis of Bathylagidae represented the most remarkable pattern of metamorphosis. Of many interesting events covering every aspects of body organization, reversible process of ossification across the metamorphosis might be most remarkable new evidence. These drastic morphological changes were associated with ontogenetical vertical migration from subsurface to mesopelagic habitats. Ox-eye tarpon having leptocephalus larval stage also revealed similar changes of body organization including shrinkage of body length. On daily age analysis, its metamorphosis process was divided into four phases including the occurrence of long term resting phase which is a new aspect of metamorphosis study with possible importance. Thus, in some typical cases, fish metamorphosis showed the close resemblance to the relevant events of amphibians.
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