| Yellow catfish Pelteobagrus fulvidraco is one of the commercial aquaculture species in China, which has delicious taste with little bone among muscle, and high nutritional value. But its small body and slow growth restrict the development of its aquaculture industry. Many studies have reported that polyploid fish especially triploid fish show better growth and reproductive performance than normal diploid fish, which are benefit for fish breeding and traits improvement. In the present study, cold shock and heat shock methods were both used to induce polyploid P. fulvidraco. The main results are summarized as follows:1. Cold shock method was used to induce triploid fish through two different designs. In the single factor design experiment, the treatment time after fertilization (TA) ranged from 1 to 6 min with the 1 min interval, the deal temperature (T) ranged from 0 to 12℃with 3℃interval , the duration time (D) ranged from 5 to 50 min with 5 min interval. Considering the survival rates in gastrula and incubation periods, the rates of deformities, aneuploids and triploids, the optimized treatment condition was recognized as TA 2 min, T 5℃, D 20 min. In this trial, triploidy induction rate was as high as 70 % in embryonic period. In the orthogonal design experiment, TA was set at 1, 2, 3 min with T being 4, 5, 6℃and D being 15, 20, 25 min. It had an identical optimized inducing condition as in the single factor design experiment, and the rate of polyploidy induction was similar to that in the single factor design experiment. Furthermore, the rate of polyploidy individuals was 25 % in juvenile period. Through the orthogonal design analysis, the results showed that starting time was the most important factor to the rates of hatching and triploid induction at embryonic stage. Additionally, some deformities were produced under cold shock treatment.2. In the heat shock orthogonal design, TA was set at 1, 2, 3 min, T at 38, 40, 42℃, and D at 1, 2, 3 min. The results showed that the optimized treatment condition was 2 min after fertilization, at 40℃for 2 min. The inducing rate of triploids was nearly 60 % in embryonic stage, and 40 %～50 % in juvenile stage with low inducing rate of aneuploids. The results demonstrated that the heat shock temperature was the most important factor to the inducing rates of triploids, deformities and relative survival at hatching stage.3. Through the comparison of effects after cold and heat shocks, it is suggested that the results in heat shock was better than that in cold shock. The inducing rate of triploids by cold shock was a little higher than that by heat shock. However, cold shock led to lower survival rate, more aneuploids and deformities.4. Through comparing the results with different treated methods, the best culture conditions for tail fin of larval fish were through using AIM for fin disinfecting, and adding growth factors as tissue cultured conditions, which can provide good materials for chromosome preparation. The best conditions for chromosome preparation were using 0.5μg/mL colchicum 2～3 h, and 0.075 M KC1 40 min to deal with samples.5. The results of ploidy identification by FCM using fin or red blood cells, and by chromosome counting were consistent, which both can get accurate ploidy level of fish. However, the histogram from FCM using fin had a larger CV, while the histogram from FCM using red blood cells had a better dispersancy, with easy operation and less tissue sampling.6. In the induced groups, a few heteroploid fish which had haploid and triploid cells was found in embryonic stage individuals, while it was not identified in juvenile. These results indicated that haploids and aneuploids can be induced by cold or heat shock treatment, but whether they can survival is disputed and need further study.
|
PDF Full Text Request