Does Dietary Sodium Alginate with Low Molecular Weight Affect Growth, Antioxidant System, and Haemolymph Parameters and Alleviate Cadmium Stress in Whiteleg Shrimp (Litopenaeus vannamei)?

Crosstalk Between Protein Restriction and Fasting and Its Impacts on Growth, Digestive Enzymes, Immunity, Antioxidant Activity, and Relative Genes of Whiteleg Shrimp (Litopenaeus vannamei)

Feed strategies such as compensatory growth and protein restriction have been applied to optimize growth and feed efficiency in aquatic species. The effects of protein restriction (from 1 to 4 weeks of feeding with dietary 35% protein) and 1 week of fasting on growth, body composition, hemolymph parameters, digestive enzymes, serological enzymes, immune and antioxidant system, and relative gene expressions in whiteleg shrimp (Litopenaeus vannamei) (0.30 ± 0.03 g) were investigated. Treatments were experienced in 1 out of 8 weeks of fasting but not in the Control and 35%P groups. Other groups were 7P40 (1-week fasting), 6P40 (1-week feeding dietary 35% protein), 5P40 (2-week feeding with dietary 35% protein), 4P40 (3-week feeding dietary 35% protein), and 3P40 (4-week feeding dietary 35% protein). The results indicated that there was no difference in weight gain among Control (10.22 g), 7P40 (9.37 g), and 6P40 (9.27 g) groups. Feed efficiency in 35%P was significantly lower than in Control. The 5P40, 4P40, 3P40, and 35%P treatments had lower protein and lipid contents in the body, protease, total protein, and cholesterol compared with the Control. Immunity and antioxidant systems were suppressed by the application of fasting and protein restriction simultaneously so that acid phosphatase, lysozyme, superoxide dismutase, glutathione peroxidase, and lysozyme gene in 4P40, 3P40, and 35%P treatments were lower, and also, these groups had higher alanine aminotransferase levels than the Control. In conclusion, this study suggests that applying both protein restriction and fasting impairs the growth and health of whiteleg shrimp, and at least 6 out of 8 weeks, whiteleg shrimp should be fed with a dietary 40% protein.

Assessing Metal Toxicity on Crustaceans in Aquatic Ecosystems: A Comprehensive Review

Residual concentrations of some trace elements and lightweight metals, including cadmium, copper, lead, mercury, silver, zinc, nickel, chromium, arsenic, gallium, indium, gold, cobalt, polonium, and thallium, are widely detected in aquatic ecosystems globally. Although their origin may be natural, human activities significantly elevate their environmental concentrations. Metals, renowned pollutants, threaten various organisms, particularly crustaceans. Due to their feeding habits and habitat, crustaceans are highly exposed to contaminants and are considered a crucial link in xenobiotic transfer through the food chain. Moreover, crustaceans absorb metals via their gills, crucial pathways for metal uptake in water. This review summarises the adverse effects of well-studied metals (Cd, Cu, Pb, Hg, Zn, Ni, Cr, As, Co) and synthesizes knowledge on the toxicity of less-studied metals (Ag, Ga, In, Au, Pl, Tl), their presence in waters, and impact on crustaceans. Bibliometric analysis underscores the significance of this topic. In general, the toxic effects of the examined metals can decrease survival rates by inducing oxidative stress, disrupting biochemical balance, causing histological damage, interfering with endocrine gland function, and inducing cytotoxicity. Metal exposure can also result in genotoxicity, reduced reproduction, and mortality. Despite current toxicity knowledge, there remains a research gap in this field, particularly concerning the toxicity of rare earth metals, presenting a potential future challenge.