Internal Fertilization of Oviparous Fishes, Oryzias Celebensis: Is It a Coincidence?

Oryzias celebensis is an oviparous endemic fish of Sulawesi. Compared to its Japanese counterpart (Oryzias latipes), this fish has not been studied much. The purpose of the article is to expand its study. The scientific novelty proves that internal fertilization in Oryzias celebensis is a part of reproductive strategy. It is not fortuitous. In the laboratory, we do routine work to breed female and male brood stock to produce embryos for ecotoxicology testing. We accidentally found an internally fertilized egg when we were stripping a female brood stock that had fertilized it externally two days earlier. These findings, combined with data on successful artificial insemination of Oryzias latipes and sperm motility of O. latipes, seem strong enough to reject the mainstream view that internal fertilization in the Oryzias genus is the facultative internal fertilization that occurs coincidentally. A new view of fertilization of O. celebensis will produce a new discourse in ecotoxicology studies.