Two types of gynogenetic diploids were arti®cially induced in the red sea bream (Pagrus major Temminck et Schlegel), either by suppressing the ®rst cell cleavage (mitotic-G2N) or by retaining the second polar body (meiotic-G2N). The eggs of red sea bream were inseminated with UV-irradiated (3000 erg mm )2 ) sperm of Japanese parrot ®sh (Oplegnathus fasciatus Temminck et Schlegel), and hydrostatic pressure shock of 700 kg cm )2 for 5.5 min at 46 min after insemination (mitotic-G2N) and cold shock of 1°C for 30 min at 3 min after insemination (meiotic-G2N) were applied to the eggs, sequentially. The total hatching rate and hatching rate of normal larvae of the normal diploid, meiotic-G2N and mitotic-G2N were 86.5 and 94.9%, 38.1 and 45.8%, and 12.8 and 35.0%, respectively. The induction of mitotic-G2N was con®rmed by isozyme marker analysis. The standard deviations, variances and coecients of variation of the body weight, standard length and body depth in 91-day-old juveniles were always large in mitotic-G2N, small in normal-2N and intermediate in meiotic-G2N. The variances in the number of pectoral ®n rays and caudal ®n rays of mitotic-G2N were signi®cantly higher than those of normal-2N. The incidences of deformities were highest in the mitotic-G2N group. The survival rates and growth performance of the meiotic-and mitotic-G2N were signi®cantly lower than those of normal-2N. Both G2N survived for 3 years to the adult stage. Determination of the optimum UV dose to genetically inactivate spermThe 1 ml of sperm of Japanese parrot ®sh was diluted 50-fold in BSS (NaCl, 8.00 g; KCl, 0.45 g; CaCl 2 , 0.20 g; NaHCO 3 , 0.02 g L )1 ), and exposed to ultraviolet (UV) radiation at 65 erg mm )2 s )1 according to the method of Onozato and Yamaha (1983). UV dose was tested between the range of 0±16 000 erg mm )2 (0±263 s). The sperm (2 ml) were used to inseminate about 1300 red sea bream eggs in sea water. Approximately 150 of the eggs were put into two 1-L beakers and incubated at 18°C. The hatching rate of each dose was recorded. Production of meiotic-and mitotic-G2NThe eggs from one female red sea bream were divided into three groups; two groups were inseminated with UV irradiated

Two types of gynogenetic diploids were arti®cially induced in the red sea bream (Pagrus major Temminck et Schlegel), either by suppressing the ®rst cell cleavage (mitotic-G2N) or by retaining the second polar body (meiotic-G2N). The eggs of red sea bream were inseminated with UV-irradiated (3000 erg mm )2 ) sperm of Japanese parrot ®sh (Oplegnathus fasciatus Temminck et Schlegel), and hydrostatic pressure shock of 700 kg cm )2 for 5.5 min at 46 min after insemination (mitotic-G2N) and cold shock of 1°C for 30 min at 3 min after insemination (meiotic-G2N) were applied to the eggs, sequentially. The total hatching rate and hatching rate of normal larvae of the normal diploid, meiotic-G2N and mitotic-G2N were 86.5 and 94.9%, 38.1 and 45.8%, and 12.8 and 35.0%, respectively. The induction of mitotic-G2N was con®rmed by isozyme marker analysis. The standard deviations, variances and coecients of variation of the body weight, standard length and body depth in 91-day-old juveniles were always large in mitotic-G2N, small in normal-2N and intermediate in meiotic-G2N. The variances in the number of pectoral ®n rays and caudal ®n rays of mitotic-G2N were signi®cantly higher than those of normal-2N. The incidences of deformities were highest in the mitotic-G2N group. The survival rates and growth performance of the meiotic-and mitotic-G2N were signi®cantly lower than those of normal-2N. Both G2N survived for 3 years to the adult stage.