Origins and Mechanisms of Diadromy in Fishes

生态方法：对白斑红点鲑、樱花钩吻鲑、银鲑、日本鳗鲡、杜父鱼、虾虎鱼和三棘鱼等几种洄游鱼类进行了生态学研究。生理方法：睾酮的管理促进了上游迁移的行为，抑制了向下迁移的马苏鲑鱼幼鱼和未成熟的kokanee，这表明睾酮在决定向海迁移或居住在河流中的重要作用。高剂量的睾酮可诱导雄性鳗类的产卵行为和雌性鳗类的挖掘行为。寄生途径：洄游淡水鳗类安圭拉被单殖吸虫假指环虫属寄生，它们和宿主鱼一起从海洋生活适应到淡水生活。日本鳗和澳大利亚鳗上的两种伪指环虫的sRNA ITS区碱基序列同源性较低，表明日本鳗和澳大利亚鳗的伪指环虫分别在日本和澳大利亚独立进化。种群遗传学方法：估计osmerid鱼类的分子遗传学表明，香鱼独特的双端性可能首先起源于osmerid谱系。对42个同工酶基因座的遗传变异进行了分析，结果表明，在内陆型和海润型红鲑中，未发现有遗传多态性，而在红鲑中，有2个基因座存在高度多态性。在进化过程中，船闸事件可能导致遗传变异性的降低。建模方法：通过数学建模研究了洄游鱼类洄游策略的进化及其与其他性状的协同进化。卵的大小和迁移时间的协同进化被认为是，并讨论了其相关性的物种的洄游鱼类。

Ecological Approach : Ecological studies were performed for several diadromous species, such as white-spotted charr, masu salmon, coho salmon, dolly verden, Japanese eel, freshwater sculpins, freshwater gobies and threespine stickleback. The life-history parameters concerning their growth, movement, reproduction and metamorphosis were solved.Physiological Approach : Administration of testosterone facilitated the upstream migratory behavior and suppressed the downward migration in the masu salmon smolts and immature kokanee, suggesting an important role of testosterone in determination of the seaward migration or residence in a river. High administration of testosterone induced a quivering in male and a digging behavior in female in the kokanee.Parasitological Approach : Diadromous freshwater eels Anguilla are parasitized with the monogenean Pseudodactylogyrus spp., which have adapted from marine to freshwater life together with the host fish. A lower homology in the base sequence of the ITS region of sRNA between two species of Pseudodactylogyrus on the Japanese eel and Australian eel suggested that the eel Pseudodactylogyrus had co-evolved independently in Japan and Australia, respectively.Population genetic Approach : Estimated molecular phylogeny of the osmerid fishes suggested that the unique amphidromy of ayu might derive first in the osmerid lineage. Genetic variability of 42 isozyme loci between landlocked kokanee and sea-run sockeye salmon revealed that no genetic polymorphism was observed in kokanee, while high polymorphism was detected at two loci in sockeye salmon. Decrease of genetic variability could be caused by land-lock event during evolutional process.Modeling Approach : Evolution of migration strategies of diadromous fish and its coevolution with other traits were studied by mathematical modeling. Coevolution of egg size and timing of migration was considered, and its relevance to speciation of diadromous fish was discussed.