| Scapharca kagoshimensis belongs to the Mollusca,Bivalvia,Pteriomorphia,Arcoida,Arcidae,Scapharca,and is commonly known as Maoge,Mahan,Walengzi,etc.It is distributed from the Yalu River in the north to Guangxi in the south.Laizhou Bay,Bohai Bay,Liaodong Bay,Haizhou Bay and Xiangshan Bay are particularly rich in resources.It is an important economic shellfish.It is not only delicious in meat,but also high in protein,low in fat,and high in vitamin content.In recent years,due to overfishing and environmental changes,the natural resources of S.kagoshimensis have become increasingly scarce,which is far from meeting the market demand.In addition to artificial breeding,marine ranching or releasing of S.kagoshimensis have been adopted in many areas to restore the S.kagoshimensis resources.With the continuous expansion of the scale of marine ranching or releasing,the research related to the environmental adaptability of S.kagoshimensis and the selection of substrate lagged behind,which affected the development of the whole industry.Temperature,air exposure,and type of substrate size are important factors that affect the growth and survival of S.kagoshimensis,and Exploring their influence on S.kagoshimensis is of great significance for improving the effects of stock enhancement and release.In this study,the effects of air exposure,high temperature stress and substrate size on the physiological metabolism and burrowing behavior of S.kagoshimensis were studied.The research results are as follows:(1)In order to study the effects of air exposure of S.kagoshimensis physiological metabolism,measure the filtration rate after air exposure of S.kagoshimensis for 2,4,8,12,24,36,48 and 72 h,and measure the whole organization pyruvate kinase(PK),hexokinase(HK)and succinate dehydrogenase(SDH),superoxide dismutase(SOD),acid phosphatase(ACP)activity and the content of adenosine triphosphate(ATP)after air exposure for 0,2,6,12,24 and 48 h.The results showed that the water loss rate of S.kagoshimensis reached 32.4% and the death rate was over 33.3% after continuous air exposure for 48 h.The activities of PK,SDH and ACP increased firstly and then decreased,and reached the maximum values at 24,12 and 6 h respectively.Compared with the control group,the activities of SOD and HK decreased firstly and then increased,and reached the minimum value at 12 h.ATP content increased rapidly after air exposure and decreased to the level of control group12 h laterly,indicating that S.kagoshimensis may change from aerobic metabolism to anaerobic metabolism.In order to evaluate the recovery of oxygen consumption rate and filtration rate of S.kagoshimensis after air exposure stress,the S.kagoshimensis with air exposure for 48 h were put into water of 20 °C,and the filtration rate and oxygen consumption rate were measured 6,12,24 and 48 h after being put back.The results showed that the filtration rate remained at a low level before 24 h,and then continued to increase significantly.The oxygen consumption rate increased significantly after reaching the minimum value at 12 h.The results showed that 12-24 h of air exposure was the period when the metabolism and related enzyme activities of S.kagoshimensis changed greatly.S.kagoshimensis can adjust the feeding and physiological metabolism levels,so that the body can recover to normal state as soon as possible after air exposure stress,the air exposure time should be controlled within24 h during seedling transportation.(2)The oxygen consumption rate and ammonia excretion rate the activities of pyruvate kinase(PK),hexokinase(HK),succinate dehydrogenase(SDH),superoxide dismutase(SOD),cytochromatic C oxidase(COX)and the contents of adenosine triphosphate(ATP)in the whole tissues of the S.kagoshimensis were measured at different temperatures(20,24,28 and 32 ℃,with 20 ℃ as the control group).The results showed that the oxygen consumption rate and ammonia discharge rate of the S.kagoshimensis increased with the increasing temperature,and reached the maximum value at 32 °C.The activities of PK,HK and SDH increased with the increasing temperature,and generally increased firstly and then decreased with the time.PK activity reached the maximum value at 12 h after heat stress treatment,while HK and SDH activities reached the maximum value at 24 h.ATP content was significantly higher than that of the control group under 28 and 32 ℃,and SOD activity increased with the increase of temperature and time,and reached the maximum value under 32℃ and at 72 h.COX activity increased with the increasing temperature,and generally increased firstly and then decreased with the time.The research indicated that high temperature 32 °C had the significant influence on the respiration metabolism and immune enzyme activity of S.kagoshimensis,and caused damage to the respiration,metabolic function and immune system of S.kagoshimensis.Therefore,the prevention and control work of heat stress S.kagoshimensis culture should be done as far as possible in summer.(3)In order to explore the influence of temperature and substrate size on the behavior of burrowing of S.kagoshimensis at different body sizes,the indexes including initial burrowing time,maximum depth of burrowing and burrowing rate of large and small S.kagoshimensis(average shell length are 21.15 mm and 9.78 mm,respectively)under different temperature and substrate size were measured in laboratory.The results showed that the initial burrowing time and maximum depth of burrowing of the small S.kagoshimensis were significantly lower than that of the large S.kagoshimensis,and the burrowing rate of the small S.kagoshimensis was significantly higher than that of the large S.kagoshimensis,indicating that the small S.kagoshimensis could adapt to the substrate environment faster and burrowing to avoid predators.The initial burrowing time of the two sizes of S.kagoshimensis at 12 °C was significantly higher than those at 20,25 and 32 ° C,and the maximum depth of burrowing and burrowing rate at 12 and 32 °C were significantly lower than those of the other two temperature groups,indicating that both excessively low temperature and high temperature had obvious inhibitory effect on S.kagoshimensis burrowing behavior.The initial burrowing time of the two sizes S.kagoshimensis in the sea mud was significantly longer than those in the sea sand groups,and the maximum depth of burrowing and burrowing rate of the S.kagoshimensis in the sea mud were significantly lower than those in the sea sand groups.The burrowing speed of the S.kagoshimensis in the sea mud was slow and the burrowing rate was lower,indicating that the substrate size had a significant effect on the burrowing behavior of the S.kagoshimensis,and the sand mud was more suitable for the survival of the S.kagoshimensis. |
