Research Of Inducing Triploid Half-smooth Tongue Sole (Cynoglossus Semilaevis) And The Cross-species Ssr Study In Flatfishes

Half-smooth tongue sole (Cynoglossus semilaevis) is an important economic fish in china, which has delicious taste with high nutritional value and grow fast in aquaculture. Many studies have re orted that polyploid fish especially triploid fish show better growth and reproduetive performance than normal diploid fish, which are benefit for fish breeding and traits improvement. The study research the induction of triploid by cold shock and optimize cold shock conditions. Moreover, the microsatellite markers derived from Spotted halibut (Verasper variegatus) deposited in our previous islation were selected for cross-species amplification in the related species, and we analyzed 20 and 18 microsatellite loci in 30 individuals of the wild population to estimate genetic variation in Pointhead flounder (Cleisthenes herzensteini) and frog flounder (Pleuronichthys cornutus), respectively. The results of the study as follows:1.The study was made to optimize cold shock conditions for producing triploid half smooth tongue sole (Cynoglossus semilaevis) by inducing second polar body extrusion. It could give relative higher rate of triploidy upto 35% for treating the fertilized eggs for 20 minutes in 4℃seawater4-5 minutes after fertilization. Male and Female chromosome types were determined to be ZZZ and ZWW, and appeared in 1:1 ratio. ZZW chromosome type was not observed, which suggest that crossing over between Z and W chromosomes was inhibited in half-smooth tongue sole。2.216 microsatellite markers derived from Spotted halibut (Verasper variegatus) deposited in our previous islation by the construction of satellite-enriched genomic library were selected for cross-species amplification in the 3 related species. 137 markers were successfully amplified in barfin flounder (Verasper moseri), and 82 of these loci were polymorphic. 95 markers were successfully amplified in Cleisthenes herzensteini, and 35 of these loci were polymorphic. 90 markers were successfully amplified in Pleuronichthys cornutus, and 18 of these loci were polymorphic. These results showed that the higher amplification rate of spotted halibut microsatellite markers in Verasper (V. moseri) and the lower rate in the other genura (C. herzensteini and P. cornutus), thus verified the relationship between the conservation of the microsatelite sequence and the genetic distance of the species.3.The number of alleles in C. herzensteini informative loci ranged from 5 to 14, with an average of 9.5 alleles per locus. The observed and expected heterozygosity ranged from 0.1724 to 1.0000 and 0.5850 to 0.9226, respectively. 6 loci deviated from the HWE in the sampled population after Bonferroni correction (adjusted P value < 0.0025). The number of alleles in P. cornutus polymorphic loci ranged from 6 to 14, with an average of 10.22 alleles per locus. The observed and expected heterozygosity ranged from 0.3846 to 1.0000 and 0.6810 to 0.9286, respectively. 7 loci deviated from the HWE in the sampled population after Bonferroni correction (adjusted P value < 0.002777). The results show that these microsatellite markers are helpful for studies of the population structure of the species.