| Pacific oyster(Crassostrea gigas)is an euryhaline and eurythermal shellfish with the advantages of rapid growth and hardiness.Its breeding scale and production is the world's largest in the aquaculture,which has made an important contribution to the economic growth and the improvement of the people's living standard in China.The annual output of aquaculture in China was 4.57 million tons in 2015,which is an important marine aquaculture species in China.In recent decades,with the development of people's living standard,the market demand for high quality oysters was ascending.Therefore,it is of great significance to carry out the genetic improvement of nutritional quality and new strain of Pacific oyster.Glycogen content is a very important traits of Pacific oyster.However,the current research on the content of glycogen is still relatively small.And the theoretical basis of breeding on it is weak.In this paper,the related research on the traits of glycogen content of Pacific oyster was carried out.The aim of this study was to provide theoretical and practical basis for the successful breeding of Pacific oyster with high glycogen content.The main results are as follows.1.Study on the larva's stocking density and adult breeding density of high glycogen content strainThe high glycogen content strain was obtained by using the partial factor mating design to construct the whole sibling family by using the individuals of the Pacific oyster with high glycogen content obtained after two generations of family breeding.In order to explore the effect of culture density on growth and survival,the growth traits and survival rates of larvae and adults were studied in this paper.The results were as follows.(1)In the larvae breeding density of 1-2/ml,3-4/ml,6-8/ml,there was no significant difference between the three groups(P> 0.05).So there is no need to pursue a low density during larval cultivation,6-8/ml can meet the needs of breeding.There was no significant difference between the low density group(10/layer)and the medium density group(20/layer)in growth phenotype.However,the growth traits of the high density group(40/layer)were lower than those of the former two groups(P<0.05).As the density increases,the mortality rate increases significantly.Therefore,in the process of adult oyster breeding,it is very useful to reduce the breeding density reasonably2.Effects of different aquaculture model on growth traitsIn order to explore the effect of different farming methods on growth traits,contrast experiments of cage culture and creping culture,comparison of shell sanding and normal culture were set.The results were as follows.(1)The growth traits of the individuals of creping culture group were significantly larger than those of the cage culture group(P<0.05).(2)There was no significant difference between the experimental group and the control group(P>0.05).The shellfish of the Pacific oyster were regenerated in a short time after being worn.3.Analysis on physiological metabolism in reciprocal cross families of high glycogen content line of Pacific oysterIn order to discover the course of the differences of physiological metabolisms between selfing lines and reciprocal crosses of Crassostrea gigas with different glycogen content,the filtration rate,oxygen consumption rate and ammonia excretion rate were studied under certain temperature(20°C)and salinity(32).In terms of the filtering rate,the result showed that the highest occurred in selfing group AA and the lowest occurred in selfing group BB.The difference between them was significant(P<0.05).There was no significant difference between reciprocal group AB and reciprocal group BA.And the value is between selfing group AA and selfing group BB.The heterosis value of the reciprocal cross was 8.44%.In the oxygen consumption rate,selfing group BB is the highest and reciprocal group AB is the lowest.There was significant difference between AA and BB(P<0.05).And the heterosis value of the reciprocal cross was-43.87%.The oxygen consumption rate was negatively correlated with the glycogen content.And the correlation coefficient was-0.884,which was reaching extremely significant level(P<0.01).In the ammonia excretion rate,there were no significant differences among all groups.It is about 0.04 mg NH3-N/(g· h).In summary,the difference between the groups mainly existed in the water filtration rate and oxygen consumption rate.This study could provide important physiological metabolic germplasm reference for the breeding of high glycogen content line of C.gigas.The ammonia excretion rate of both strains increased with increasing temperature and reached the maximum at 28°C.4.The effects of temperature and salinity on the physiological metabolism of high glycogen content strain of Pacific oysterIn order to investigate the effects of temperature and salinity on the physiological metabolism of high glycogen content strain of Pacific oyster,the filtration rate,oxygen consumption rate and ammonia excretion rate of strain H and L were studied at different temperatures(16°C,20°C,24°C,28°C,30°C,32°C)and salinity(15,20,25,30,35).The results were as follows.(1)The filtration rate of strain H and strain L increased with the increase of temperature.When the temperature was 28°C,the filtration rate reached its maximum.After 28°C,the water treatment rate began to decrease.The oxygen consumption rate of strain H increased with the increase of temperature and reached the maximum at 32°C.The oxygen consumption rate of strain L increased with the increase of temperature,reached the maximum at 28 ° C,and decreased after 28°C.The content of glycogen in the two strains decreased with the increase of temperature,and the decrease of strain H was significantly higher than that of strain L.(2)With the increase of salinity,the filtration rate of strain H and strain L increased continuously.When the salinity reached 30,the filtration rate reached the maximum value,and decreased when the salinity exceeded 30.Oxygen consumption rate and ammonia excretion rate showed the same trend with the filtration rate.The glycogen content of strain H remained stable in the range of salinity 15-25,and decreased significantly after salinity 25.The glycogen content of strain L did not change much in the whole salinity gradient,but the sugar content level was generally lower than that of strain H. |
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