ELECTROPHORETIC STUDIES OF MEIOTIC SEGREGATION IN INTERSPECIFIC AND INTRASPECIFIC HYBRIDS AMONG EAST-ASIAN SPECIES OF THE GENUS ORYZIAS (PISCES, ORYZIATIDAE)

Three species of Oryzias, namely, O. curvinotus, O. luzonensis, and four subspecific groups of O. latipes, have been found in East Asia. In order to elucidate the genetic relationships among these species, fertility and meiotic segregation in hybrids were examined. Fertile males and females and normal segregation were observed in intraspecific crosses of O. latipes and in interspecific hybrids between O. luzonensis and O. curvinotus. By contrast, male sterility and production of non-reductional 2n eggs by female were observed in interspecific crosses between O. latipes and O. curvinotus. Similar results were obtained with luzonensis-latipes hybrids. These results demonstrated that O. luzonensis and O. curvinotus are closely related, and that reproductive isolation is complete between O. latipes and O. luzonensis and between O. latipes and O. curvinotus.