The role of the anal fin in fertilization success in male medaka, Oryzias latipes

抄録

The anal fin of the medaka Oryzias latipes is sexually dimorphic, with mature males developing a larger anal fin than females. To determine the functions of the male anal fin during mating, an anal fin-removal experiment was conducted. Males were mated with females in successive treatments in which different portions of the anal fin were removed. Male medaka with half of their anal fin removed fertilized a significantly lower proportion of eggs than did males with a normal anal fin. The results show that the anal fin in male medaka is important for efficient fertilization, suggesting selection for a larger anal fin.