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The effects of silver nano/microparticles (AgP) on juvenile Litopenaeus vannamei shrimp were evaluated through several responses, aiming to use it as a prophylactic and therapeutic method. Shrimps (3.19 ± 0.13 g) were exposed to clear water for 3 h with increasing concentrations of nanosilver (0; 25; 100; and 400 μg/l). After 3 h of exposure, they were transferred to water without nanosilver for 30 days (recovery). The weight gain and weekly growth were not affected by AgNP. Total antioxidant capacity (ACAP) increased in the hepatopancreas (exposure period) and gills (recovery) in shrimp exposed to AgNP. In muscle, ACAP was induced in shrimp exposed to 100 μg/l AgNP (exposure). In the gills, there was an increase in TBARS in shrimp exposed to 100 μg/l AgNP (recovery). In the concentration of protein-associated sulfhydryl groups (P-SH), a decrease was observed in the hepatopancreas (recovery) in the 100 μg/l AgNP treatment. In chromaticity parameters, an increase in reddish tones was observed in shrimp exposed to 100 μg/l AgNP (recovery). An increase in granular hemocytes was verified in shrimp exposed to 25 and 400 μg/l AgNP during exposure. Tissues analyzed histologically showed normal patterns without apoptosis or necrosis processes, and after 30 d of recovery, only in one muscle sample of shrimp exposed to μg/l of AgNP was silver detected. It is concluded that a prophylactic action of short duration (3 h) mostly did not affected the welfare of shrimp L. vannamei and can be considered its use as a therapeutic strategy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Inc.)

Saxitoxin (STX) is a neurotoxic cyanotoxin that also generate reactive oxygen species, leading to a situation of oxidative stress and altered metabolism. The Amazonian fruit açaí Euterpe oleracea possesses a high concentration of antioxidant molecules, a fact that prompted us to evaluate its chemoprotection activity against STX toxicity (obtained from samples of Trichodesmium sp. collected in the environment) in the shrimp Litopenaeus vannamei. For 30 days, shrimps were maintained in 16 aquaria containing 10 shrimps (15% salinity, pH 8.0, 24 °C, 12C/12D photoperiod) and fed twice daily with a diet supplemented with lyophilized açaí pulp (10%), in addition to the control diet. After, shrimps (7.21 ± 0.04 g) were exposed to the toxin added to the feed for 96 h. Four treatments were defined: CTR (control diet), T (lyophilized powder of Trichodesmium sp. 0.8 μg/g), A (10% of açaí) and the combination T + A. HPLC analysis showed predominance of gonyautoxin-1 concentrations (GTX-1) and gonyautoxin-4 concentrations (GTX-4). The results of molecular docking simulations indicated that all variants of STX, including GTX-1, can be a substrate of isoform mu of the glutathione-S-transferase (GST) enzyme since these molecules obtained similar values of estimated Free Energy of Binding (FEB), as well as similar final positions on the binding site. GSH levels were reduced in muscle tissues of shrimp in the T, A, and T + A treatments. Increased GST activity was observed in shrimp hepatopancreas of the T treatment and the gills of the A and T + A treatments. A decrease of protein sulfhydryl groups (P-SH) was observed in gills of shrimps from T + A treatment. A reduction in malondialdehyde (MDA) levels was registered in the hepatopancreas of the T + A treatment in respect to the Control, T, and A treatments. The use of açaí supplements in L. vannamei feed was able to partially mitigate the toxic effects caused by Trichodesmium sp. extracts, and points to mu GST isoform as a key enzyme for saxitoxin detoxification in L. vannamei, an issue that deserves further investigation., (Copyright © 2022. Published by Elsevier B.V.)

This study evaluated the effect of dietary inclusion of lyophilized açaí Euterpe oleracea (LEO) on redox status of shrimp Litopenaeus vannamei (initial weight 1.5 ± 0.39 g) upon exposure to cyanotoxin nodularin (NOD) in bioflocs system. Three hundred juvenile shrimps were randomly divided into two groups and fed twice a day with two diets: one containing 0.00 (control diet) and the other 10.0% LEO (w/w) for 30-days. After the feeding period, both shrimp groups were submitted to three treatments (14 L; 7 shrimp/tank) with different concentrations of cyanotoxin NOD (0.00; 0.25; and 1.00 μg/L) dissolved in water with 96 h of exposure. Then, the shrimps were sampled (n = 15/treatment) for the determination of reduced glutathione (GSH), the activity of glutathione-S-transferase (GST), sulfhydryl groups associated to proteins (P-SH), and lipid peroxidation (TBARS) in the hepatopancreas, gills and muscle. The NOD accumulation was measured in the muscle. The results revealed that dietary LEO significantly increased GSH levels in the hepatopancreas and gills of the shrimps exposed to NOD. Toxin exposure did not modify GST activity in all organs. Muscle TBARS levels were lower in the shrimp fed with the LEO diet and exposed to NOD. The NOD toxin did not accumulate in the muscle but notably was detected in the control groups fed or not with dietary LEO. Açaí was able to induce the antioxidant system of L. vannamei, as well as lowered the oxidative damage in shrimps exposed to NOD, suggesting its use as a chemoprotectant against cyanotoxins., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)