Yasunori Koya

Learn More
We found that male small-egged Kajika, Cottus pollux SE sensu Yokoyama and Goto (2005), retained a large volume of urine (approximately, 1 % body weight) in their urinary bladder while nesting under spawning substrate. This increase in urine volume occurred three days after the males were transferred to the nesting tank. Serum 11-ketotestosterone (11-KT)(More)
We found two patterns of parasitic mating behaviors by male in Japanese medaka, Oryzias latipes, in the spawning by one female and two males in the aquarium condition. In the first type of parasitic mating behavior, the unpaired male would rush toward the closely adhering female and paired male, and simultaneously perform emission behavior with close(More)
Although renal hypertrophy during the reproductive period has been reported previously in species of Cottus, the function of the kidney in reproduction remains unknown. In order to clarify the role of the kidney in reproduction, seasonal changes in gonad and kidney weight, serum androgen levels, kidney histology, and the protein content of urine, were(More)
Males of the viviparous teleost fish Gambusia affinis copulate with females by using a specialized anal fin, or gonopodium. When female G. affinis were placed in a shallow transparent tank which was then floated on the surface of a larger aquarium housing male G. affinis , the males frequently attempted to copulate with females housed in the smaller(More)
  • 1