サンゴ礁魚類の性分化, 性転換機構の形態学的, 生理学的研究.pdfVIP

19 サンゴ礁魚類の性分化，性転換機構の形態学的，生理学的研究 ＊1，2 ＊1，2 ＊1 中村 將 ・小林靖尚 ・三浦さお り Morphological and Physiological Studies on Sex Differentiation and Sex Change in Coral Reef Fish Masaru NAKAMURA＊1，2,3 , Yasuhisa KOBAYASHI＊1，2 and Saori MIURA＊1，2 Abstract In addition to gonochorism, several types of hermaphroditism are seen in fish. Individuals of some fishes bear gonads containing both mature ovary and mature testis. Some fishes change sex from male to female (protandrous sex change), others change from female to male (protogynous sex change), and a few can change sex either way and multiple times (bothway sex change). In many cases, sex change is cued by social factors, such as the disappearance of a male or female from a group. These phenomena reveal that the mechanisms of sex determination and sex differentiation in fishes, in being diverse and more plastic, differ from those of other higher vertebrates. First, our research focuses on analyzing the mechanism of sex differentiation in gonochoristic fish, using genetically controlled all-female and all-male tilapia Oreochromis niloticus. Second, we examined the sex change from an endocrinologic viewpoint, using morphological, physiological, and molecular techniques. In order to further characterize protandrous, protogynous, and bothway sex changes, we carry out experimental studies with the sea anemone fish Amp hip rion clarkii, the three spotted wrasse Halichoeres trimaculatus and the honeycomb grouper Ep inep helus merra, and the gobiid fish Trimma okinawae,