Preliminary Studies On Growth Performance And The Resistance To High Ammonia And PH In Chinese Shrimp Fenneropenaeus Chinensis

Chinese shrimp Fenneropenaeus chinensis is a commercially important speciesin China and the natural distribution is confined only in the Bohai Sea, Yellow Seaand the coast of Korean Peninsula. During the 1990s, the yield of Fenneropenaeuschinensis from farming ponds counted for 70% of the total marine shrimp farmingproduction. However, because of the factors of strains, diseases and environment, theyield decreased sharply, which counted for a quarter of the annual harvest in theprosperous stage and the economic losses reached to tens of billion RMB. Mostshrimp farmers rely on the capture of wild shrimp to stock their ponds, and there areconcern that harvesting wild shrimp for aquaculture may cause poor diseasesresistance, gene losses and degradation of good traits, which can not satisfy with thesustainable development of shrimp farming, so Studies on selective breeding of newshrimp strains must be strengthened so as to establish the genetic breeding system.Particularly, the selective breeding should be focused on those traits like growth,stress and disease resistance. Here, Genetic analysis linked to growth and stress-resistancetraits in Fenneropenaeus chinensis was studied on the basis of the selectivebreeding of Fenneropenaeus chinensis New Variety "Huanghai No. 1". The mainresults are as follows.1. The Comparison of Growth Pattern in "Huanghai NO. 1" and the First Generationof Wild Population in Chinese Shrimp Fenneropenaeus chinensisFour growth models were used to fit the growth pattern of morphologicalcharacters in the new variety "Huanghai NO.1" and the first generation of wild population in Fenneropenaeus chinensis based on fifteen morphological characters.The squared multiple correlation coefficient (R2) of the Cubic growth model was thehigh most than Line model, Power model and Exponential model, so the Cubicgrowth model was selected to investigate the growth pattern and age in month atinflexion. The results showed that ages in month at inflexion of body weight in"Huanghai NO. 1" and the first generation of wild population were 2.87 (body weightat inflexion was 14.98g) and 4.05(body weight at inflexion was 26.26g), respectively.The ages in month at inflexion of other morphological characters in "Huanghai NO. 1"were from 0.51 to 3.07. CL had the most rapid growth rate, followed by AW, CH, AH,CW, BL, FL, AL5, AL3, AL4, TL, AL2, AL1, and AL6 had the slowest growth rate.The ages in month at inflexion of other morphological characters in the firstgeneration of wild population were from 2.38 to 3.08, except that of AL2, and theorder of achieving the most rapid growth rate was AL2, AL1, AL3, AL4, CH, AL5,CW, FL, AH, AW, TL, CL, BL, and AL6, that delayed one month than that of"Huanghai NO. 1" except AL2 and AL1.2. Studies on heritability and correlation for growth traits in Chinese shrimpFenneropenaeus chinensisFifty-one full-sib families (including thirty-five half-sib families) of the Chineseshrimp Fenneropenaeus chinensis were obtained by artificial insemination. Fourgrowth traits of these families were measured, including body length, cephalothoraxlength, abdorminal segment length and body weight. According to quantitativegenetics theory, the heritability of each growth trait, genetic and phenotypiccorrelation among the traits was statistically studied. The results show that theheritabilities were 0.36～0.51 for body length, 0.14～0.24 for cephalothorax length,0.25～0.50 for abdominal segment length, and 0.04～0.29 for body weight. Geneticcorrelations were high between growth traits. The genetic correlation between bodyweight and abdominal segment length was the highest (0.920), followed by bodylength and abdominal segment length(0.915), body length and body weight(0.880),body weight and cephalothorax length(0.870), abdominal segment length andeephalothorax length(0.861), The genetic correlation between body length and cephalothorax length was the lowest(0.832). The estimates of phenotypic correlationwere from 0.795 to 0.905 with a high significant difference (P＜0.01) among the fourgrowth traits by t-test.3. Candidate markers linked to growth traits in Fenneropenaeus chinensisRandom Amplified Polymorphic DNA (RAPD) technique was applied to analyze150 samples of three populations from the large body population (CP-a) and the smallbody population (CP-b) which were from the sixth generation of cultured populationsof Fenneropenaeus chinensis and from the wild populations (WP). 240 randomprimers were screened for mixed templates and 65 differential fragments correlatedwith growth traits were obtained including 55 positive fragments and 10 negativefragments. Population analysis used primers screened from 240 RAPD primersshowed 9 RADP markers were correlated with growth traits including 7 positivemarkers and 2 negative markers. After cloning and sequencing we got 8 sequencesvarying in length from 500bp to 1000bp except marker amplified by S159.PrimerPremier 5 software was used to design specific primers on the basis of the sequenceand Sequence-Characterized Amplified Regions (SCAR) technique was used toinvestigate growth traits markers of Fenneropenaeus chinensis. There were 6 pairs ofprimers (SCAR1, SCAR2, SCAR3, SCAR4, SCAR5 and SCAR6) can obtainamplified products, but the fragments from the former four pairs of primers did notdifferentiate in three populations. The latter two pairs of primers amplifiedpolymorphic fragments according to the band frequency and variety rule appeared inthe samples. The numbers of polymorphic fragments amplified by primer SCAR5 inCP-a, CP-b and WP were 39,26 and 27, respectively, and the band frequencies were78%, 52% and 54%, respectively.χ2 test of polymorphic fragments in CP-a and WPpopulations showed significantly different (P＜0.05), that indicated the polymorphicfragment from SCAR can be used as positive marker candidate.3 alleles and 6genotypes were found in three populations amplified by primer SCAR6, while onlyCP-b had the allele A, that revealed that locus A maybe was correlative or linkagewith some gene which can restrain growth speed of Fenneropenaeus chinensis. Theresults demonstrate that the two SCAR markers we had identified can he used as markers candidate correlated with growth traits of Fenneropenaeus chinensis andsupplied theory basis for marker-assisted selection (MAS) in the practice.4. Comparison for the Resistance to pH and Ammonia in Chinese ShrimpFenneropenaeus chinensis familiesTwenty families obtained using artificial insemination were used to compare theresistance to pH and ammonia by acute toxicity. The results showed that there wereextremely significant (p＜0.01) for the resistance to pH and ammonia betweendifferent test times, and the average LD₅₀ (median lethal dose) values of 24h, 48h and72h for resistance to ammonia were 62.15,30.31 and 15.60 mg/L, respectively, andfor resistance to pH were 9.99,9.41 and 9.12, respectively. Eight families wereselected for the high resistance to ammonia, and ten families were selected for thehigh resistance to pH, while seven families were selected for the high resistance toammonia and pH According to the average LD₅₀, which provide the basic conditionfor the production of stress-resistance populations and the selective breeding ofstress-resistance lines in Chinese shrimp Fenneropenaeus chinensis.5. Analysis of heterosis and genetic correlation of growth traits and the resistance tostress in Fenneropenaeus chinensisThe heterosis and genetic correlation of growth traits and the resistance to stressof Fenneropenaeus chinensis were analyzed in two groups of "Huanghai No.1"(CYand HB), and the first generation of wild population based on diallel cross at their ageof 150 days. The hybrids of CY×WP was found to show the highest heterosis ratewith a range of values from 2.28% to 18.20% on the four growth traits of body length,body weight, cephalothorax length and abdominal length, while the hybrids ofCY×HB and WP×CY showed the poor heterosis among the six hybridizationcombinations. High Heterosis for the resistance to high ammonia was found with arange from 12.67% to 69.33% among six hybridization combinations, the hybrids ofHB×WP showed the highest heterosis rate (69.33%). There was no heterosis inhybrids of CY×HB, HB×Wp and WP×HB for the resistance to high pH, the hybridsof WP×CY showed the highest heterosis (16.03%). The results of genetic correlationsshowed that there were negative genetic correlation between growth traits and the resistance to high ammonia and pH. The estimates of genetic and phenotypiccorrelation were 0.528～0 and -0.103～0 between growth traits and the resistance tohigh ammonia, and -0.221～0.027 and -0.042～0.005 between growth traits and theresistance to high pH, which showed the method of selection index can be used for thecomplex traits.