Effect of low salinity on acute arsenic toxicity and bioconcentration in shrimp Litopenaeus vannamei juveniles

Plantago asiatica seed as a protective agent for mitigating metals toxicity on Penaeusvannamei

Plantago asiatica seeds (PS) are commonly used as a medicinal plant. This study investigates the efficacy of PS against heavy metal toxicity in white shrimp (Penaeus vannamei). After feeding PS diet (5 g/kg) or basal diet (control group) for 7 days, shrimps were exposed to sublethal concentrations of heavy metals in seawater (As: 12 mg/L, Pb: 250 mg/L, Hg: 0.4 mg/L). The 7-day survival observation showed that the survival in groups fed with PS were significantly higher than that in the control group, revealing that dietary PS had the efficacy to mitigate heavy metal toxicity in white shrimp. Under the same feeding condition, white shrimps were exposed to safety dose of heavy metals (1/10 of sublethal concentrations) to understand the mechanism of mitigation. The metal accumulations in haemolymph, gills, hepatopancreas, and muscle tissues as well as the immune, anti-oxidative, stress related gene expressions in haemocytes, gills and hepatopancreas were measured for 14 days. The As accumulation in gills and hepatopancreas of groups fed with PS were significantly lower than those of control group on day 7 and 14, respectively; The Pb concentration in haemolymph of group fed with PS was significantly lower than that of control group on day 7 and 14; The Hg concentration in hepatopancreas of the group fed with PS was significantly lower than that of control group on day 7. Dietary PS could mitigate heavy metal-induced immune suppression, oxidative stress, and stress response by positively regulating immune (proPO I, Toll, IMD), antioxidant (SOD, GST, Trx), and negatively regulating stress response genes (HSP70, MT). The present study demonstrated that dietary PS could protect white shrimp against metal toxicity by reducing metal accumulations and regulating the immune, antioxidant, and stress response gene expressions in specific tissue. Therefore, PS may serve as a beneficial feed additive in the aquaculture.

Bioaccumulation of arsenic and immunotoxic effect in white shrimp (Penaeus vannamei) exposed to trivalent arsenic

Trivalent arsenic (As (III)) contamination in the marine environment can produce adverse effects in crustaceans. The present study investigated the chronic toxicity of As (III) in white shrimp (Penaeus vannamei) by analyzing the tissue bioaccumulation and non-specific immune responses. Shrimps were exposed to 0 (control), 50, 500, and 2500 μg/L of As (III) for 21 days. The results showed that the hepatopancreas was the main tissue of arsenic accumulation in white shrimp. The cumulative concentration of total arsenic and inorganic arsenic but not arsenobetaine was positively correlated with the exposure concentration. In vitro As (III) treatment (0-2500 μg/L) with haemocytes isolated from healthy shrimp did not cause the cytotoxicity, but this arsenic treatments inhibited the phagocytic rate and O₂^- production. Moreover, the decrease of total haemocyte count and the inhibition of phagocytic rate, phagocytic index, O₂^- production and phenoloxidase activity were observed in white shrimp under the exposure of As (III) over a period of 21 days. This study revealed that chronic As (III) stress could disturb arsenic metabolism and immune responses in P. vannamei.