| Mytilus coruscus is mainly distributed in temperate sea areas,including the East China Sea,the Yellow Sea,the Bohai Sea,Hokkaido in Japan,Jeju Island in South Korea.In China,The coastal areas of Zhejiang and eastern Fujian have large output.It is one of the common aquatic economic species in China,especially Shengsi County in Zhejiang Province.However,compared with the rapid development of mussel culture industry,the basic research of physiology and ecology related to M.coruscus culture technology is relatively backward,which restricts the healthy development of the industry.In the process of M.coruscus culture,temperature and dissolved oxygen are two common environmental stress factors,but there are few reports on the physiological and ecological response and mechanism of mussel.In this paper,the physiological and ecological responses of M.coruscus to high temperature and low oxygen were studied,and the related mechanisms were discussed.The main results of this study are as follows: 1 Clearance rate and feeding behaviors of M.coruscus after heat and hypoxia stressThe clearance rate and feeding behavior of M.coruscus were studied at three temperature levels(20℃,25℃ and 30℃,of which 20℃ is the control group,with average shell length 85.36 ± 3.93 mm)and five dissolved oxygen levels(1,2,4,6,8 ± 0.5 mg/L,the temperature is set at 20℃,and 8 mg/L is the normal oxygen control group).Under the combined stress of 30℃ and 1 mg/L,the clearance rate of M.coruscus was continuously monitored and measured at 0,6,12,24,48,96,144 h,respectively.The main results are as follows:(1)Under the stress of 30℃,the clearance rate per unit of dry tissue weight and individual clearance rate of M.coruscus decreased,and the shell opening of M.coruscus decreased;(2)Under the stress of 20℃ and 1 mg/L,the clearance rate per unit dry weight and individual clearance rate decreased,and the shell of M.coruscus was almost closed;(3)Under the combined stress of 30℃ and 1 mg/L,the clearance rate per unit dry weight and individual clearance rate of M.coruscus increased first and then decreased,which was basically lower than that of the control group(20℃ and conventional oxygen).2 Respiratory metabolism of M.coruscus after heat and hypoxia stressThe oxygen consumption rate and ammonia excretion rate of M.coruscus were studied at three temperature levels(20℃,25℃ and 30℃,of which 20℃ is the control group,with average shell length 85.36 ± 3.93 mm)and five dissolved oxygen levels(1,2,4,6,8 ± 0.5 mg/L,the temperature was set at 20℃,and 8 mg/L is the normal oxygen control group).Under the combined stress of 30℃ and 1 mg/L,the oxygen consumption rate and ammonia excretion rate of M.coruscus were monitored and measured at 0,6,12,24,48,96,144 h.The main results are as follows:(1)Within the range of 20-30℃,the oxygen consumption rate of M.coruscus increased with the rising of temperature,and the ammonia excretion rate first increased and then decreased.The critical temperature of M.coruscus may be in the range of 30-34℃.(2)When DO was 1 mg/L,the oxygen consumption rate decreased and the ammonia excretion rate increased.(3)Under the combined stress of 30℃ and 1 mg/L,the oxygen consumption rate of M.coruscus in 24 h were affected to some extent,and with the extension of the double stress time,there might be a risk of death.3 The activities of related enzymes of M.coruscus after heat and hypoxia stressThe activities of respiratory metabolizing enzyme,non-specific immune enzyme,antioxidant enzyme,and digestive enzyme in different tissues of M.coruscus were studied at three different temperature levels(20℃,25℃ and 30℃,of which 20℃ is the control group,with average shell length 85.36 ± 3.93 mm)and five dissolved oxygen levels(1,2,4,6,8 ± 0.5 mg/L,the temperature was set at 20℃,and 8 mg/L is the normal oxygen control group).The activities of enzymes were measured at 0,6,12,24,48,96,144 h,respectively.The main results are as follows:(1)The AKP activity and ACP activities in the membrane,gill and hepatopancreas of M.coruscus treated at 30℃ were lower than those of the control group,and the high temperature would inhibit the activity of the hydrolase involved in the immune system.The activity of AKP and ACP in the liver and pancreas of M.coruscus treated with 1 mg/L was lower than that of the control group,and the non-specific immune function of hydrolysis system of M.coruscus was inhibited by short-term hypoxia stress.(2)The activity of SOD in the membrane of M.coruscus treated at 30℃ was significantly higher than that in the temperature control group,and the activity of SOD in gill was significantly lower than that in the normoxia control group.Under the combined stress of high temperature and low oxygen,the membrane of M.coruscus plays a more important role in the antioxidant defense.(3)LDH activity in the membrane and hepatopancreas of M.coruscus treated at 30℃ and 1 mg/L increased,which indicated that acute high temperature and low oxygen could promote anaerobic metabolism of M.coruscus.The PK activity of the membrane of M.coruscus in the treatment group of 30℃ was significantly higher than that in the control group of 1 mg/L.The membrane of M.coruscus is more sensitive to the combined stress of high temperature and low oxygen.(4)In the temperature range of 20-30℃,there was no significant effect on AMS and LPS activities in the hepatopancreas of M.coruscus;the high temperature inhibited the digestion ability in the hepatopancreas of M.coruscus to cellulose,and the optimal temperature of pepsin in the hepatopancreas of M.coruscus might be 25℃.Short-term hypoxia reduced AMS,LPS and cellulase activities in the hepatopancreas of M.coruscus,and its digestive capacity may depend on pepsin secreted by tissue.The activities of the four digestive enzymes reached a high level in 24 hours.(5)The activities of non-specific immune enzyme,antioxidant enzyme,respiratory metabolizing enzyme and digestive enzyme were tissue-specific. |
