Abstract
This study was conducted to understand the changes of physiological and biochemical indexes of black and red shell Pinctada fucata under acute high and low salt stress. In this study, the salinity of 35‰ was used as the control, while the salinities of 20 and 50% salinity were used as the low and high salt treatment groups, respectively. The osmotic pressure (OSM) and ion concentration in the hemolymph, Na+-K+ -ATPase (NKA) activity and respiratory metabolism in gills, and antioxidant and immune (non) enzymes in the hepatopancreas of P. fucata with two shell colors were compared and analyzed at the time periods of 1.5 and 3 h post-salinity stress. The results showed that the OSM and inorganic ion (Na+, Ca2+, and Cl–) concentration in the hemolymph of the black and red P. fucata increased significantly with the increase of salinity after the time periods of 1.5 and 3 h. At 3 h, the black P. fucata NKA activity decreased significantly with the increase of salinity, while red P. fucata reached the highest value at high salinity. The succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) activities of red P. fucata showed U-shaped and inverted U-shaped distributions with the increase of salinity after 1.5 h, respectively. With the increase of salinity, the phenoloxidase (POX) activity of red and black P. fucata showed inverted U-shaped and U-shaped distributions, respectively. The contents of glutathione (GSH) and vitamin C (VC) in black P. fucata decreased significantly with the increase of salinity at 1.5 and 3 h. Red P. fucata GSH and VC reached their maximum value in the 1.5-h low salinity group and 3-h high salinity group. The vitamin E (VE) content in black P. fucata increased significantly with the increase of salinity at 1.5 h, and reached the maximum at 3 h in the control group. Red P. fucata VE reached the maximum at 1.5 and 3 h in the control group. The results obtained from the present study revealed that the sensitivity of P. fucata to salinity varied in shell color. Compared to black P. fucata, red P. fucata responds more quickly to sharp salinity changes, thereby reducing more likely damage. Compared with a high salt environment, P. fucata was more adaptable to the changes of acute low salt environment. The results obtained from the present study provide the physical references for subsequent selective breeding of this species.
Highlights
Pinctada fucata, belonging to mollusks, bivalves, Pinctada and Pinctada family mainly distributed in the tropical and subtropical area, is one of the main shellfish species for cultivating seawater pearls in China (Sun et al, 2021)
Evidence has indicated that temperature, salinity, dissolved oxygen, and pH can change the physiological indexes of P. fucata, including osmotic pressure (OSM), oxygen consumption rate, ammonia excretion rate and cellular immune level, disturb balance basal metabolism, inhibit growth, and even lead to death (Yang, 2016; Liu, 2018; Sun et al, 2021)
The biochemical parameters of hepatopancreas and gills tissue were determined according to the instructions of the manufacturer using commercial kits (Nanjing Jiancheng Biological Co., Ltd., Nanjing, China and Abbkine Scientific Co., Ltd., Wuhan, China), i.e., lactate dehydrogenase (LDH) (Item No KTB1110): 2,4-Dinitrophenylhydrazine method; Na+-K+ -ATPase (NKA) (Item No KTB1800): Inorganic phosphorus method; succinate dehydrogenase (SDH) (Item No A022-1-1): Phenazine methosulphate method; phenoloxidase (POX) (Item No H247): competition method; LZM (Item No A050-1-1): Micrococcus Lysodeik-ticus method; glutathione (GSH) (Item No A006-2-1): Ellman reagent colorimetric method; vitamin E (VE) (Item No A008-1-1): Phenanthroline colorimetry method; vitamin C (VC) (Item No A009-1-1): Xylene dichloroindophenol colorimetry method; and total protein (Item No A045-4-4): bicinchoninic acid method
Summary
Pinctada fucata, belonging to mollusks, bivalves, Pinctada and Pinctada family mainly distributed in the tropical and subtropical area, is one of the main shellfish species for cultivating seawater pearls in China (Sun et al, 2021). Since 1949, P. fucata has been cultivated in Hainan and Liangguang (Guangdong and Guangxi) Provinces of China until pearl production peaked in the 1990s (Ai et al, 2003; Yang et al, 2017). P. fucata has greatly promoted the development of pearl industry in China and created considerable economic income for the nation. Massive mortalities of P. fucata are frequently reported and have caused considerable economic losses in the past 10 years. Evidence has indicated that temperature, salinity, dissolved oxygen, and pH can change the physiological indexes of P. fucata, including osmotic pressure (OSM), oxygen consumption rate, ammonia excretion rate and cellular immune level, disturb balance basal metabolism, inhibit growth, and even lead to death (Yang, 2016; Liu, 2018; Sun et al, 2021). All the evidence reveal that massive mortality of P. fucata is closely related to these environmental changes
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