Aquaculture Reports (Dec 2024)
Growth performance, enzyme activities and metabolite level response to low pH stress in juvenile red swamp crayfish Procambarus clarkii
Abstract
The red swamp crayfish Procambarus clarkii is the most widely farmed shrimp in China but often encounters low pH stress during seedling cultivation in paddy fields. Two experiments were conducted: the first aimed to determine the semi-lethal concentration (LC50) of juvenile P. clarkii and the second to evaluate the survival, growth, enzyme activities, and metabolic level of juvenile P. clarkii for 21 days in a low-pH environment. The LC50 pH values of juvenile P. clarkii at 24, 48, 72, and 96 h were 2.85, 2.98, 3.32, and 3.44, respectively. Over 21 days, mortality rates at pH 3.5, 5.5, and 7.5 were 61.24 ± 3.01 %, 20.20 ± 5.40 %, and 9.62 ± 5.73 %, respectively. Weight gain and specific growth rates were lowest at pH 3.5, improved at pH 5.5, and highest at pH 7.5. Enzymatic activity of amylase, lipase, and protease was significantly reduced at pH 3.5 compared to pH 7.5 (P < 0.05). Similarly, phenyl oxidase, acid phosphatase, and alkaline phosphatase activities were notably lower at pH 3.5 and 5.5 on day 7 but gradually recovered over time. By day 21, lysozyme activity remained significantly lower in the pH 3.5 and 5.5 groups than in the pH 7.5 group (P < 0.05). The metabolism of sphingosine, agmatine, 2-phenylethanol, phenylethylamine, and deoxyguanosine was inhibited in pH 3.5 and 5.5 groups, which decreased nutrient digestion and slowed the growth of young crayfish. The metabolic levels of corticosterone, lipoxin B4, arachidonic acid, and prostaglandin A1 were significantly increased in pH 3.5 and 5.5 groups and activated immune factors to combat the influence of adverse environment. Our findings suggest that juvenile P. clarkii is highly adaptable to low pH; however, prolonged low pH stress significantly increases their mortality and inhibit their growth performance due to reduced activities of digestive and immune enzymes.
