Studies on the diversity and creative mechanism of the reproductive mode in copulating teleost fishes

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The present studies carried out a ecological and physiological examination on Scorpaeniformes cottoid species, with the focus of the spawning mode and functional morphology of testes as out-adaptive traits for evolution of copulating behavior.1. Histological observation for investigation of on ovarian annual cycle showed that Radulinopsis taranetzi and R. darjevini, maternal care and copulating fishes, are potential multi-spawners. Experimentally, females of these species spawn two times in a breeding season only when the egg masses was taken out of aquarium tank before hatching, but both spawned only one time when the females succeefully protected the first egg mass until hatching. These results suggested that the second clutch of these cottids is for compensatory eggs when the first clutch was eaten during developing.2. Histological observation on testes showed that copulating period and sperm strage system in testicular organ differed between R. taranetzi and R. darjevini. R. tarane … More tzi copulates for six months from January to July, while R. darjevini for ten months from September to July. In the latter fish, testis weight is relatively heavier and sperm is stored more compactly as sperm bunch than those of the former. In addition small chamber, which is enclosed with connective tissues, is provided near the opening of the tip of penis. It is plausible that these morphological differences function to emit much sperm into female genital tract for intensive sperm competion (long copulaing period).3. A non-copulating sculpin, Hemilepidotus gilberti, produce much apyrene spermatozoa with plural nuclei during spermatogenesis. The function of apyrene sperm were investigated with fluorescent dye and microsatellite DNA polymorphism. It was showed that the sperm played as a broker toward sneaker's eusperm for sperm-competition. In addition it is experimentally showed that apyrene spermatozoa have antidispersive function.4. The past studies indicated that copulating cottoids are multispawers while non-copulating cottoids are single spawner. Multi-spawning brought much benefit for copulating individuals but not benefitial for non-copulating fishes. The present study investigated for Radulinopsis species, showed that the above concept may not adaptive for at least maternal care and copulating fishes. Less