Study On Effects Of Temperature And Salinity During Early Life Histroy, Selective Breeding And Genetic Law Of Color Character In Chlamys Nobilis(reeve)

Central composite circumscribed experimental design and response surface and desirability function analysis method was employed to study effects of different combinations of temperature-salinity on the fertilization rate, hatching rate, and to investigate the synthetic effects of temperature and salinity on growth and survival of larvae in Chlamys nobilis(Reeve) when fed with same algae. The effects of different combinations of temperature and salinity on C.nobilis were simultaneously quantified via experiments, the effective regression equations were established to predict the optimum conditions of combinations of temperature and salinity for fertilization, hatching, larval growth and survival. The aim was to provide theoretical basis to cultivate seedlings of C.nobilis. Also studied were the effects of parental selection in C. nobilis, with the shell length as breeding objective trait, under a certain selection pressure, by divergent selection for large, medium, small groups of the parental generation, through conventional farming technology and relatively consistent environmental conditions of three groups in terms of egg yield, fertilization rate, hatching rate, larval and adult growth and survival. This study revealed parental selection effects would be helpful to resolve the problem of parental selection in breeding, and to improve the total yield of C.nobilis. In developing family lines, the genetic law of four kinds of color, orange and glaucesecent for shell, yellow and white for adductor was studied. Both shell and adductor colors will act as selection breeding characters.The results showed that:1) In the study of combined effects of temperature and salinity on fertilization rate and hatching rate, larval growth and survival of C.nobilis, the results showed that temperature and salinity were the important environmental factors in the stage of embryonic development, moreover, the influence of temperature was greater than salinity; there was no interaction effect between the two factors in certain range (P>0.05). With the larval development, the adaptability of C.nobils to temperature and salinity increased gradually, larval growth become faster, but in the experimental 20 days (the period from the straight hinge larvae to metamorphosis), even at the best temperature and salinity conditions, the survival rate still decline gradually. The relationship between temperature, salinity and fertilization rate, hatching rate, larval growth (including Instantaneous Growth Rate, IGR and Accumulated Growth Rate, AGR) and survival could be described as follows(P <0.0001): YF R= 14.5629 + 0.4162T + 0.6879 S 0.0019T S 0.0073T 2 0.0110S2Y HR= 7.4653 + 0.2093T + 0.3605 S 0.0010 TS 0.0037 T 2 0.0057S2102 2Log ( IGR _ SL2 0+ 0.10) = 22.5235 + 1.0406T + 0.7439 S 0.0023T S 0.0204T 0.0115S102 2Log ( AGR _ SL2 0+ 0.05) = 2 0.7681 + 1.0184T + 0.6450 S 0.0020T S 0.0204T 0.0100S2 2 2 2SR2 =2 489.0452 + 129.7093T + 131.6882S 5.1856T S 1.6921T 1.7926S + 0.0430T S + 0.0115TS2 2 2 2SR1 1 = 2 191.3604 + 119.5690T + 94.1474 S 3.1964T S 2.1215T 1.1097 S + 0.0463T S +0.1334TS2 2 2 2SR2 0 =1 502.8306 + 63.9194T + 74.6224 S 1.7813T S 1.0338T 1.0720 S + 0.0192T S +0.1337TS (where T is temperature, S is salinity, SR2,11,20 is the survival rate of days 2, 11 and 20. IGR-SL20 is instantaneous growth rate of shell length, AGR-SL20 is accumulated growth rate of shell length.)By applying the response surface and desirability function to optimizing effects of temperature and salinity on the fertilization rate, hatching rate simultaneously, the suitable temperature and salinity of fertilization and hatching were 22-27℃, 26-30‰, respectively. The optimum point was found at temperature of 24.7℃, and salinity of 29.3‰. At this optimum point, fertilization rate and hatching rate reached 70.86% and 39.09%, respectively. Growth (accumulation and instantaneous growth) and survival of the best combination of temperature and salinity were 25.04℃, 29.53‰and 24.6℃, 28.03‰, respectively.2) Divergent Selection was used to estimate the realized heritability of C.nobilis with shell length as objective traits, also the growth performance of different groups were compared. the results showed that in terms of egg yield, fertilization rate, hatching rate, metamorphosis rate, juvenile acquisition rate, survival across the transition period at sea and other indicators, there were significant differences between 3 groups (P<0.01). In addition, the growth of shell length, body weight daily growth and other metrical traits were also very significantly different in every period (P<0.05). It was shown by ANOVA that large-size group was significantly better than the middling group (P<0.05), and middling group significantly better than the small-size group (P<0.05) in respect of fertilization rate, hatching rate, metamorphosis rate, juvenile acquisition rate, survival over the transition period at sea, larval growth rate, juvenile and adult stages. Selective reponse of shell length of large-size group reached 9.47±2.01, 3.16±1.24 for the middling group, -10.04±3.14 for small-size group. The selective reponse of the body weight of large, medium and small-size groups in turn was 5.13±1.22, 1.87±0.55, and -19.24±4.78. The realized heritabilities of shell length and weight were 0.96±0.24 and 0.44±0.13, respectively. These results suggest that gene of shell length exist pleiotropy, excellent polygene of large-size group to a certain degree of accumulation, and expressed through offspring economic character phenotypic value; on the contrary, the number of harmful genes of the small size group has been further homozygous, while leading to increased mortality of offspring, on the other hand, inhibited significantly the growth of their offspring later. Breeding is essentially in a group of excellent gradually improve breeding group of gene frequency process, through homogeneous optional choose and concentration will pass to the next generation, excellent genetic groups of offspring and excellent genotype frequency also increase. The experimental results of selection is required to the next generation can genetic breeding to verify next breeding3) Recessiveness and/or dominance in shell color and adductor color had been investigated in the study of genetic law of two kinds of shell color and two kinds of adductor color in C.nobilis, respectively. Orange shell color was dominant over glaucesecent, white adductor color dominant over yellow. Both the orange shell color and white adductor color had two kinds of genotypes, viz., homozygosity(all yellow for shell and all white for adductor) and heterozygosity(3:1,χ2<χ02.05,1). The glaucesecent shell color and yellow adductor color were recessive homzygotes.