| Chromosome manipulations in left-eyed flounder and large yellow crocker were carried out by temperature or hydrostatic pressure shock after fertilization. Allozyme analysis was used to investigate the genetic structure and variation in cultivated stocks of P. crocea. The main results were shown as follows:Under the intensity of 3770ergs/mm2, UV light irradiation had slight effects on the ultra-structure, survival and mobility of sperm, while over this intensity, UV light irradiation would cause the damage of sperm ultra-structure and mobility. Therefore the optimal UV dosage for genetic inactivation of sperm of P olivaceus was determined as 3770ergs/mm2 in terms of survival, haploid percentage after irradiation.The optimal conditions for mitogynogenesis induction in P. olivaceus were tested by varying the treatment timing, intensity and duration of application of pressure or cold shocks. Treatment optima for cold shocks were 1-2℃for 45 min at 85 min after fertilization (AF) and 600 kg/cm2 for 6 min at 85 min AF for pressure shocks (water temperature, 15±0.2℃). Ploidy determination was carried out by chromosome counting, flow-cytometry and larvae morphological observation. Under the optimal treatment, survival rate of mitogynogenetic diploid larvae in pressure treatment group at hatching stage was 13.01% , which was much higher than those in cold shock group (less than 1%), indicating that pressure shock was more effective than cold shock for inhibiting the first cleavage of eggs of P. olivaceus. Survival rates of mitogynogenetic diploid larvae at 1-4d post-hatching (PH) were markedly lower than those of their diploid control and meiogynogenetic counterparts at the same stage even though no significant differences were observed in total length of their larvae between them before first feeding.The optimal conditions for meiogynogenesis induction in the second generation of gynogentic P. olivaceus were carried out by changing the treatment timing, intensity and duration of application of pressure or cold shocks. Treatment optima for cold shocks were 0–1℃for 45 min at 5 min after fertilization (AF) and 480 kg/cm2 for 5 min at 5 min AF for pressure shocks. G2 meiogynogenetic diploids were obtained by fertilizing gynogentic eggs with UV-irradiated homologous normal sperm (UV intensity, 3770 erg/mm2) and pressure or cold shocking eggs as above. Ploidy investigations were also performed on experimental groups by chromosome counting, flow-cytometry and larvae morphological observation. Under the optimal treatment, survival of embryo 12h AF and larvae at 6h PH and deformed hatchling rate in cold shock group were 84.34±1.7%,53.32±5.57%,15.42±1.79%; while those indices in pressure group were 86.32±5.07%,79.14±2.11%,8±1.43%, respectively, which showed that pressure treatment was more effective than cold shock for retention of the second polar body of eggs from gynogenetic P. olivaceus under either small batch or large volume scale and had less harm to the subsequent embryonic development and larval survival. Survival of G2 gynogenic larvae at 1-4d PH induced by either cold or pressure shock was not different significantly, but markedly lower than that of their diploid control at the same stage. No significance (P<0.05) was observed in total length of larvae between G2 meiogynogens and their control before first feeding.Horizontal starch gel electrophoresis of allozymes was used to investigate genetic variation and stock structure of Fujian and Zhejiang cultivated stocks of P. crocea. 34 loci of 12 allozymes and their expression patterns in 4 tissues (eye, muscle, heart and liver) were examined and recorded, respectively. The results showed that allozyme expression patterns in cultivated stocks of P. crocea were tissue- specific. At the 95% confidence level, 7 Polymorphic loci (Aat-1, Aat-2Acp-1, Mdh-3, Mdh-4, Mep-1, Mep-4) in Fujian stock and 10 Polymorphic loci (Aat-1, Aat-2, Acp-1, Gpi-2, Gpi-3, Mdh-3, Mdh-4, Mep-1, Mep-4, Sdh) in Zhejiang stock were detected. The proportion of polymorphic loci (P, 29.41%), average alleles (A, 1.32) and average heterozygosity (H, 0.06534) in Zhejiang stock were higher than those in Fujian stock (P, 20.58%; A, 1.24 and H, 0.03366). The genetic deviation index (d) indicated that a deficit of heterozygosity existed in both stocks and 7 of 10 polymorphic loci except for Acp-1, Gpi-2 and Gpi-2 in Zhejiang were significant depart from Hardy-Weinberg equilibrium by X2-test (p<0.05) stock. This result showed that severe inbreeding might have existed in P. crocea cultivated stocks due to generations of intensive culture without addition of wild broodstock. The genetic similarity (I) and genetic distance (D) between these two stocks were 0.9984 and 0.0016, respectively, indicating a close genetic affinity of two stocks.The optimal conditions for triploid induction in P. crocea were performed by pressure and cold shocks. The treatment optima for cold shock were 3-4℃for 10min at 3min AF or 450kg/cm2 for 3min at 3 min AF for pressure shock. In terms of survival, deformed hatchling and triploidy rates, pressure treatment was more efficient and suitable than cold shock in triploidy induction of P. crocea. Cold and pressure treatments had effects on embryonic development of P. crocea and embryonic development of both shock groups were suppressed and the first cleavage were delayed 27min in cold shock groups while 17 min in pressure shock groups compared to their control. But the difference was decreased with embryonic development and disappeared before early blastula stage in pressure group and early gastrula stage in cold group. Putative triploid group had a similar growth performance compared to their diploid counterparts during 20-90 d after hatching even though diploids were smaller in body weight and total length (differences not significant). But 90 -120d after hatching, weight gain in putative triploid group was significant higher than that in control group while difference in length gain at the same stage was not distinct (P<0.05).
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