| Haliotis discus hannai is one of the important cultured economic shellfish in China.Because its meat is tender,delicious and nutritious,it is deeply loved by consumers.Among them,the price of abalone with wrinkles raised by bottom sowing is higher because of its bigger size and fatter meat quality.In this study,the growth data of Haliotis discus hannai under two different bottom seeding environments(habitat construction area and non-habitat construction area)in Sanggou Bay area were measured.It was found that the growth rate of Haliotis discus hannai was faster in the habitat construction area,and the water temperature in the overwintering period in this area was-2~7 ℃.Long-term low temperature stress could affect the low temperature tolerance of the abalone,Therefore,abalone Haliotis discus hannai,which has experienced low temperature stress,was selected as the main experimental material for subsequent experiments.In order to explore the effect of low temperature on the physiology and biochemistry of Haliotis discus hannai,and to understand the effect of different culture modes on the low temperature tolerance of Haliotis discus hannai,the low temperature stress experiment was carried out on the first generation of Haliotis discus hannai under different culture modes,and the data such as heart rate,oxygen consumption and turning time were measured to evaluate the difference of low temperature tolerance.Then carry out further experiments on the 2-year-old abalone under different cultivation modes,measure its heart rate,oxygen consumption data,amino acid,carbohydrate,organic content and other nutritional indicators,explore the differences in low temperature tolerance between individuals who have undergone low temperature screening and individuals who have not undergone screening,and the differences in nutritional level and composition of the abalone under the two cultivation modes.Then the metabolic response mechanism of Haliotis discus hannai under low temperature stress was further analyzed by metabonomics.Based on various physiological data,this study analyzed the difference of low temperature tolerance and its influencing factors of Haliotis discus hannai under two cultivation modes,and preliminarily studied the physiological basis and molecular mechanism of low temperature tolerance through molecular biological methods.(1)The growth data of abalone Haliotis discus hannai under two different bottom seeding environments were measured.In view of the possible fouling biological attachment problems during the bottom seeding process,the biological control experiments were carried out on Thais clavigera Kuster、Ceratostoma rorifluum and Cantharus cecillei.The results showed that the growth rate of shell length of abalone seedlings in the habitat construction area was 35.6% higher than that of individuals in the non-habitat construction area,and the wet weight increased by 84.7%.In terms of nutrient composition,the total sugar content,total organic matter content and essential amino acid content of abalone in the habitat construction area were significantly higher than those in the non-habitat construction area(P<0.05).In the pollution biological control experiment,the average number of oysters living on the abalone in Cantharus cecillei group was(0.04± 0.04)per oyster,the average number of oysters living in Thais clavigera Kuster group was(2.49 ± 0.91)per oyster and the average number of oysters living in Ceratostoma rorifluum group was(2.21 ± 1.05)per oyster,and the number of control group was(3.33± 0.46)per oyster.Three kinds of snails were significantly lower than the control group,and Cantharus cecillei were also significantly lower than the other two kinds of snails(P<0.05).The results showed that the growth rate of abalone was faster in the habitat construction area,and the habitat construction was beneficial to the growth of abalone.The three kinds of snails have significant control effect in the biological control experiment of fouling,and Cantharus cecillei have the strongest effect in preventing and controlling oyster adhesion.(2)The parameters of nutrient components such as total sugar,protein,total organic matter and amino acid content in the muscle tissue of the north and south relay cultured abalone and the north bottom seeded cultured abalone were measured,and the physiological indexes such as oxygen consumption rate and heart rate under low temperature stress were measured.The results showed that the total sugar content,total organic matter content and essential amino acid content of the bottom sown individuals were(3.20 ± 0.00)%,(27.60 ± 3.70)% and(4.19 ± 0.09)%,which were significantly higher than those of the north-south relay individuals(P<0.05).Under low temperature stress,the oxygen consumption rates of the individuals in the relay culture and bottom sowing culture were(0.017 ± 0.006)and(0.018 ± 0.009)mg/(g · h),respectively,with no significant difference(P>0.05);However,the heart rate of bottom sown individuals was(12.82 ± 1.72)BPM,which was significantly lower than that of relay cultured individuals [(18.11 ± 2.79)BPM](P<0.05).The results showed that different cultivation modes significantly affected the nutritional value of individuals cultured abalone Haliotis discus hannai and their physiological process in response to low temperature stress,and the individuals cultured at the bottom had higher nutritional value and low temperature tolerance.(3)The low temperature stress experiment was conducted on the first age individuals of the offspring of Haliotis discus hannai under two cultivation modes.The data of heart rate,oxygen consumption rate and turnover time of Haliotis hannai hannai under normal temperature(24 ℃)and low temperature(9 ℃)were analyzed.The results showed that when the temperature dropped slowly,the heart rate of abalone in the bottom seeding group decreased 2.82 BPM/℃,and that in the raft group decreased 2.48 BPM/℃.There was no significant difference between the two groups(P>0.05).When the temperature dropped suddenly,the heart rate of abalone in the two groups also had no significant difference(P>0.05).However,when the temperature dropped from 24 ℃ to 9 ℃,there was a significant difference between the heart rate of abalone in the bottom seeding group and the raft group.The difference between the heart rate of abalone in the bottom seeding group was(39.09 ± 2.36)BPM,and that in the raft group was(34.42 ± 5.23)BPM,It shows that individuals of abalone discus hannai in the bottom seeding group have higher heart rate regulation ability.The abalone of the two experimental groups showed strong activity at normal temperature of 24 ℃,and could quickly adjust the turnover when the stomach and feet were exposed.The turnover time of the bottom seeding group was(0.95± 0.07)min,and that of the raft group was(0.67 ± 0.35)min,with no significant difference(P>0.05).At 9 ℃,the turning time of the bottom seeding group was(9.9 ±2.85)min,and that of the raft group was(17.19 ± 5.69)min.There was no significant difference between the two groups(P>0.05).The oxygen consumption rates of abalone in bottom seeding group and raft group were(0.115 ± 0.006)and(0.099 ± 0.016)mg/(g · h)respectively at 24 ℃,and(0.024 ± 0.010)and(0.023 ± 0.006)mg/(g · h)respectively at9 ℃.There was no significant difference in oxygen consumption rate between bottom seeding group and raft group at the same temperature(P>0.05).Although the heart rate of individuals in the bottom seeding group was slightly lower than that of individuals in the raft group in the low temperature environment,no significant difference was detected in the statistical analysis results.However,in the difference of heart rate between normal temperature and low temperature treatment,there is a significant difference between the bottom seeding group and the raft group,and the bottom seeding group has a higher ability of heart rate regulation.(4)The low temperature stress experiment of abalone(Haliotis discus hannai)and raft culture abalone(Haliotis discus hannai)was carried out.Use UHPLC-Q-TOF MS metabonomics technology,PCA,OPLS-DA and other multivariate statistical analysis methods to screen differential metabolites and determine the affected metabolic pathway.The results showed that the total number of differential metabolites in the blank group KBDB vs KBFS was 87,and there was no enriched differential metabolic pathway;The total number of differential metabolites in SYDB vs SYFS in the experimental group was130,and a total of 7 differential metabolic pathways were enriched,including D-arginine and D-ornithine metabolism,protein digestion and absorption,ABC transporter,Lysine degradation,tropine,piperidine and pyridine alkaloid biosynthesis,m TOR signaling pathway,Arginine and proline metabolism.Among them,amino acid metabolism was most significantly affected,followed by protein metabolism.The results showed that there was a significant difference in metabolism between abalone and raft abalone under low temperature stress.The metabolism of amino acid and protein in abalone decreased,which could reduce energy consumption and cope with long-term low temperature environment.In addition,low temperature stress led to a significant increase in the content of trehalose,maltose and other small molecular sugars in abalone blood,which may be another response strategy of abalone to low temperature stress. |
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