Diploid gynogenesis induced by cold shock in cyprinid loach, Misgurnus anguillicaudatus. In：J.L. Maclean, L.B. Dizon and L.V. Hosillos (eds.)

Abstract

A reliable method for the induction of heterozygous diploid gynogenetic fry in the cyprinid loach, Misgurnus anguillicaudatus, was developed by means of cold shock treatment to eggs fertilized with UV-irradiated sperm. Haploid and diploid fry were identified by measuring the DNA content of erythrocytes with the use of cytophotometry. Haploid fry were totally deformed and died within four days after hatching. All morphologically normal fry were confirmed to be diploid. UV-irradiation dosage of 0.5 to 2 J/cm² was the optimum for genetic inactivation of sperm of cyprinid loach. Eggs fertilized with UV-irradiated sperm and subjected to cold shock of 8℃ for 40 min., at 3 to 5 min. after fertilization, resulted in comparatively high percentages of normal fry. As for the optimal cold shock temperature and duration for the treatments applied 4 min. after fertilization, high hatching rate and high rate of normal fry were produced from cold shock of 8℃ for 40-60 min. and 6℃ for 20-50 min.