Male Japanese rice fish can mate as many as 27 times in a single day, while females typically engage in mating just once.
The scientists observed a marked decline in sperm quantity following the tenth mating.
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The animal kingdom can get pretty weird when it comes to sex and relationships. Different creatures have evolved all sorts of methods to pass on their genes to the next generation and beat out competitors in the process. For the Japanese rice fish, researchers have discovered that it's all about how many times a day the males are getting freaky, which could be as many as 27.
Japanese rice fish – also known as medaka (Oryzias latipes) – are a small, unassuming species that live wild in the marshlands and rice fields of Japan. They are externally fertilizing fish, which means they release sperm or eggs into the water column, where they fertilize.
“Medaka are among the fish that spawn, where fertilization occurs after the eggs and sperm are released in water. As these gametes are difficult to collect, the number of sperm released and the fertilization rate during successive matings had remained a mystery,” study co-author Dr Yuki Kondo explained in a statement. “Our research group previously developed an accurate method for measuring the sperm count of medaka, which is why we we
