Externally applied steroids induced natural spawning. (A) Artificial insemination was conducted for eggs squeezed during spawning induced by a mixture of steroids (Steroid). As a control, the fertilization rate of eggs ovulated by PMSG-hCG injection was examined (hCG). Fertilisation rate (in %) was assessed by counting the number of eggs dividing to the 4 cell stage following insemination. Each value represents the mean of data from three different females. Vertical lines indicate standard deviation. (B) A photograph of frogs developed from eggs ovulated by steroids.