Effects Of Environmental Factors On Growth, Survival And RNA/DNA Ratio For Larvae And Juveniles Of Pinctada Martensii (Dunker)

In this research, we selected larvae and juveniles of Pinctada martensii (Dunker) asstudy subjects, investigated joint effects of environmental factors such as temperature,salinity, algal concentration and the rearing density on the growth, survival and RNA/DANratio of the subjects. Using composite experimental center design and response surfacemethod analysis method, linear effects, quadratic effects and interaction effects ofenvironmental factors were studied. Regression equations were established to predict theoptimum conditions for growth and survival. The purpose was to provide reference methodto cultivate seedlings of P. martensii, and provided theoretical basis for promoting thebreeding technology optimization. The content included:1. The combined effects of temperature and salinity on the larvae growth and survivalof P. martensii were studied. The pearl oyster larvaes were selected with the shell length of100-110μm. Temperature (T) controlled at18-34C, salinity (S) from22to36, and a totalof11runs were setted in the experiment, which were repeated once. The results showedthat temperature and salinity were important environmental factors for larvae’s growth andsurvival, and the influence of temperature was greater than salinity; The linear andquadratic effects of temperature and salinity on the instantaneous growth rate (IGR), theaccumulated growth (AGR) and the survival rate (SR) were significant (P<0.05), and theinteraction effect between temperature and salinity was not significant (P>0.05). Themodels about combined effects of temperature and salinity on the IGR, AGR and SR wereestablished as follows:IGR=-97.9573+3.1161T+4.2431S+0.0057T×S-0.0568T~2-0.0746S~2(R~2=0.9635; Adj. R~2=0.9521; Pred.R~2=0.9264, P<0.01)AGR=-107.54+3.1148T+4.9435S-0.0036T×S0.0536T~2-0.0828S~2(R~2=0.9735; Adj. R~2=0.9652; Pred.R~2=0.9456, P<0.01)SR=-968.951+18.6333T+54.0982S+0.0438T×S-0.3472T~2-0.9458S~2(R~2=0.9844; Adj. R~2=0.9795; Pred.R~2=0.9670, P<0.01)Showing that the equations were very significant and had a high fitting degree, could bepractically used for forecasting lavae growth and survival. According to optimize these models, the optimal combination of temperature and salinity was28C/29, while the maximuminstantaneous growth rate was9.84%/d, accumulative growth rate was8.49μm/d, thesurvival rate was89.79%and the desirability function was99.9%.2. With an average shell height of650μm as experimental materials, Studiedtemperature (18-34C), algal concentration (5×10~3-100×10~3cell/mL) and juvenile density(0.5-10ind./mL) on growth of P. martensii. It was showed that the linear effect oftemperature and algal concentration was significant on IGR (P<0.05), which of juveniledensity was highly significant (P<0.01); The quadratic effects of the three environmentalfactors were highly significant (P<0.01); The interaction effects between temperature andalgal concentration, temperature and juvenile density, algal concentration and juveniledensity influenced not significantly on IGR (P>0.05). The linear and quadratic effects oftemperature, algal concentration and juvenile density were significant on AGR (P<0.05).The combined effect between temperature and algal concentration was not significant onAGR (P>0.05), but those between temperature and juvenile density, algal concentrationand juvenile density were highly significant (P<0.01). The models about combined effectsof temperature, algal concentration and juvenile density on IGR and AGR were establishedas follows:IGR=-4.6372+0.5581T+0.0337C+0.0328D-0.0002T×C+0.0004T×D-0.0001C×D-0.0104T~2-0.0003C~2+0.0084D~2(R~2=0.9944; Adj. R~2=0.9845; Pred.R~2=0.9375, P<0.01)AGR=-69.3194+7.6780T+0.2912C*0.6264D+0.0005T×C-0.0455T×D+0.0098C×D-0.1414T~2-0.0023C~2+0.0511D~2(R~2=0.9974; Adj. R~2=0.9928; Pred.R~2=0.9588, P<0.01)Showing that the equations were highly significant and had a high fitting degree, could bepractically used for forecasting juvenile growth. According to the results of simultaneouslyoptimizing the models, the optimal combination of temperature, algal concentration andjuvenile density was27.4C/69.39×10~3cell/mL/1.03ind./mL, while the maximuminstantaneous growth rate reached3.43%/d, the maximum accumulative growth rate reached42.55μm/d, with the desirability function being100%.3. The combined effects of temperature, algal concentration and juvenile density onRNA/DNA ratio and the relationship between RNA/DNA ratio and growth on juvenilePinctada martensii (Dunker) were studied. The results showed that RNA/DNA ratio wasclosely related to the three environmental factors; The linear effect of temperature wassignificant (P<0.05), of which the quadratic effect was highly significant (P<0.01); Thelinear and quadratic effects of algal concentration were highly significant (P<0.01); The linear effect of juvenile density was highly significant (P<0.01), but the quadratic effect ofwhich was not significant (P>0.05); The combined effect between temperature and algalconcentration, temperature and juvenile density were significant (P<0.05), which betweenalgal concentration and juvenile density were highly significant (P<0.01). The model ofRNA/DNA ratio with the three environmental factors was established, it can be used toevaluate the environment condition:RNA/DNA=-6.8755+0.7666T+0.0336C-0.0477D-0.00002T×C-0.0024T×D+0.0008C×D-0.01421T~2-0.0002C~2+0.0012D~2(R~2=0.9986; Adj. R~2=0.9961; Pred.R~2=0.9821, P<0.01)RNA/DNA ratio was linearly correlated to IGR and AGR, established models were asfollows:IGR=0.09698+0.8087RNA/DNA(R~2=0.8803; Adj.R~2=0.8710; Pred.R~2=0.9382, P<0.01)AGR=-6.3626+11.5301RNA/DNA(R~2=0.9692; Adj.R~2=0.9668; Pred.R~2=0.9845, P<0.01)Showing that the equations were very significant and had a high fitting degree, could bepractically used for forecasting juvenile growth. The optimization of the response surfaceresults showed that the optimal factors combination of temperature, algal concentration andjuvenile density was27.4C/69.39×10~3cell/mL/1.03ind./mL, at which the maximumRNA/DNA ratio was4.21, the instantaneous growth rate was3.43%/d, the accumulativegrowth rate was42.55μm/d, with the desirability function as high as100%.