Effect Of Temperature On The Early Embryonic Development Of Haliotis Discus Hannai And Study On Triploid Induction By Different Salinity Treatment

Temperature and salinity arethe two main ecological factors thataffect the growth and development of marine shellfish.Early developmentalstages of shellfish embryos are too fragile to survive in considerablystringent environmental requirements,and significantly weak whileresisting the effect of temperature and salinity. As one of the mostvaluable shellfish farming, Haliotis discus hannai has a larger-scalefarming in our various coastal areas. In this paper, the effect oftemperature on Haliotis discus hannai’s early embryonic development, aswell as low-salted and high-salted-induced feasibility of producingtriploid embryos will beexplored and examined.Research is divided into the following three parts:First of all, the effect of temperature on Haliotis discus hannai’searly embryonic developmentIn this experiment, the impact of using artificial spawning techniqueson the abalone were studied, embryonic development after fertilizationeffects of various temperatures and particularly under22℃obtained byHaliotis discus hannai’s sperm and egg cells. Observation showed that:(1) Haliotis discus hannai’s eggs are able to fertilize and grow at14℃,16℃,18℃,20℃,22℃24℃,26℃temperature conditions. Asthe temperature decreases, the developmental process of embryonicdevelopment presents a trend to be slower; when the temperaturereducedto18℃or lower, the development process will stagnate at some stage(morula-gastrulation) before hatching and not able to hatch normally;at14℃growth arrest at the morula stage, at16℃growth arrest atgastrulation stage, at18℃growth stagnate at the rotation period.In the range of14-26℃, as the temperature rises, Haliotis discushannai’s fertilized egg cost shorter time to get to each phase; at24℃and26℃, malformation rate was around20%-30%which isconsiderably high although the growth rate is faster, which concludes20℃-22℃is the optimum temperature for Haliotis discus hannai’sembryonic development.(2) Haliotis discus hannai’s eggs fertilized at22℃and then grow at14-26℃. As the temperature rises, it takes shorter time for thefertilized eggs to get to each phase and the development speedaccelerateswhile the temperatureincreases; with temperature above20℃, the embryo can hatch smoothly; with temperature under22℃,90%of the embryos can hatch out trochophora within12h22min; embryonicdevelopment stalled when the water temperature is below18℃; and whenthe temperature is higher than24℃most embryos tend to be deformity.Hence, it reveals that Haliotis discus hannai’s embryosoptimum temperature range is20℃-22℃.(3) After fertilizing at optimum temperature of22℃, abalone fertilizedpolar body release continuous observation, found13min afterfertilization began to release the first polar body,33min afterfertilization begins to release the second polar body. This accuracyofthis polar body release time for polyploid inductionobservationprovidesreferencea significant aid for thefollowing research about thetiming of grasping polyploidy induction.Secondly, the salt-induced triploid Haliotis discus hannaiStep one: Selecting the salinity range12–20and sets5salinitygradient Group2:12,14,16,18,20; and5processingperiod with5min,10min,15min,20min;2processing opportunity:8min after fertilization(before the release of the first polar bodyand after fertilization28min(before the second polar body release). Using optical microscopyto observe the hatching rateof trochophora and use a flow cytometry todetect its ploidy.Salt-induced inhibition of the release of the first polar bodytriploid abalone experiments, the highest rate in triploid salinity is16for10min, triploid rate of up to45.34%; comprehensive evaluationindex (hatchability×triploid rate) to salinity20, when dealing withlong-10min treatment group was the highest,20.17%.Salt-induced inhibition of the release of the second polar body triploidabalone experiments, the highest rate in triploid salinity of12, whentreatment20min, was19.78%; comprehensive evaluation index salinity20,when dealing with the long treatment group20min highest7.85%.Comprehensive analysis showed that the best combination of low salt hannaiinduced triploid fertilization after8min, salinity20, when dealing withlong10min, comprehensive evaluation factor of20.17%.Third, the high salt-induced triploid Haliotis discus hannaiSelect the salinity range40-60, were set to5salinity gradient group5:40,45,50,55,60; while processing length and timing of inductiontreatment with salt.Experimental results show that a high salt-induced inhibition of therelease of the first polar body triploid abalone experiment, the highestrate in triploids salinity of45, when the process5min, the rate was33.46%triploid; comprehensive evaluation index salinity of45to amaximum length of5min treated group when treatment was32.24%. In theexperimental release of the second polar body pre-treatment group, thehighest rate in triploid salinity of45, when dealing with10min, was18.53%; highest treated comprehensive evaluation index salinity45,5minwhen dealing with long, was14.16%. Comprehensive analysis showed thatthe best combination of high salt-induced triploid hannai afterfertilization8min, salinity45, when dealing with long5min, comprehensive evaluation factor of32.24%.