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Context: Immunostimulants promote immune response and growth, and raise stress and aquaculture disease resistance. At times, the results are contradictory and misleading regarding their utilization. Accordingly, the following problematic was stated: Could the related scientific literature on prebiotics and probiotics that evaluate the indicators of the immune system of shrimps be the basis for decision-making in shrimp-culture immunostimulant use? Aim: To evaluate the influence of prebiotics and probiotics on the phenoloxidase expression and activity in Penaeus shrimps, using meta-analysis for decision-making in shrimp culture. Methods: Several searches were conducted in Pubmed, Science Direct, and Scopus, between 2008 and 2019, related to the influence of immunostimulants on phenoloxidase activity and gene expression. The statistical analysis was conducted by means of Metanalysis 0.9.2., with a 95% confidence interval. Results: A total of 262 scientific articles on prebiotic and probiotic evaluation in Penaeus shrimps were compiled. Out of them, 61 met the inclusion criteria for immunological response: 51 dealt with phenoloxidase activity, and 11 studied prophenoloxidase. Both prebiotics and probiotics stimulated the enzyme and proenzyme; the plant extracts had a major role in the modification of this activity, whereas the Bacilli produced the highest stimulation. Conclusions: The scientific literature on Penaeus shrimp phenoloxidase activity indicated careful evaluation due to the experimental design and way expressed in the results.

Background: The excessive use of antibiotics in shrimp aquaculture cause severe ecological damage. Immunostimulant probiotics are an alternative prophylactic treatment to enhanceantioxidant and immune response to reduce mortality induced by pathogenic microbes. Objective: This study investigated the effect of live yeast Debaryomyces hansenii incorporated in diet and in culture water on survival and expression of the antioxidant and immune-related genes in Penaeus vannamei juvenile shrimp. Methodology: Shrimp were fed daily for 10 days with treatments of different doses and a post-infection with Vibrio parahaemolyticus as follows: a) control (-) without feed additives and non-infected; b) control (+) without feed additives and infected; c) D. hansenii, 1×106 CFU g-1 feed; d) inulin, 2.5 mg g-1 feed; e) D. hansenii, 1×106 CFU g-1 feed + inulin, 2.5 mg g-1 feed; f) D. hansenii, 2×106 CFU g-1 feed + 1×106 CFU mL-1; g) D. hansenii, 4×106 CFU g-1 feed + 1×106 CFU mL-1. Relative gene expression of lysozyme (LYS), glutathione peroxidase (GPX), and superoxide dismutase (SOD) were determined in shrimp muscle and hepatopancreas previous to challenge with V. parahaemolyticus. Results: Juvenile shrimp increased the resistance to V. parahaemolyticus infections significantly more than untreated shrimp after D. hansenii administration in feed and water, and mixed with inulin. Relative gene expressions of LYS and SOD increased significantly in shrimp muscle after treated with D. hansenii and D. hansenii + inulin, respectively. SOD and GPX were significantly expressed in shrimp hepatopancreas. Implications: The findings provide new insights to apply yeast immunostimulants in reared shrimp to increase immune response and survival against experimental bacterial infections. Conclusions: In this study, juvenile shrimp exposed to additive immunostimulants increased gene expression in shrimp tissues, muscle and hepatopancreas, and the dose of 1×106 CFU g-1 of D. hansenii in feed was sufficient to increase shrimp survival against V. parahaemolyticus infection.

This study aimed to evaluate the physiological responses to stress of tambaquis (Colossoma macropomum) fed with β-glucan supplemented diet undergoing transportation in a closed system. To do so, tambaquis (35.06±0.80g; 11.8±0.09cm) were fed with a β-glucan supplemented diet (0; 0.1; 0.2; 0.4; and 0.8%.kg-1) for 60 days. After this period, fishes were transported on road for 3h in a closed system. Responses to stress were evaluated through hormonal, biochemical, and hematological indicators within the following periods: before transportation, immediately after transportation, and 24 and 48h after transportation. Immediately after transportation, there was a significant increase in the plasma concentrations of cortisol and glucose in all treatments when compared to the concentration before transportation; there was an increase in the hemoglobin concentration in fishes fed without a b-glucan supplementation diet; and there was an increase in the mean corpuscular hemoglobin in fishes fed without supplementation or supplemented with 0.1 and 0.2% of b-glucan. The results allowed us to establish that the hormonal, biochemical, and hematological changes occurred immediately after transportation, with return to the basal concentrations after 24h. β-glucan supplementation in the tambaqui diet wasn’t effective to relieve the responses to stress due to transport.

The defence against infections is the essential function of the immune system of all Vertebrates. Fish present an efficient and developed immunologic response and in the case of Teleosts, with some similarities to the higher vertebrates. It can be divided into two types: innate or non specific and adquired or specific, both with a humoral and cellular compartments. Their relative importance can change according to the age of fish and is always under the influence of different factors. The most relevant components are mentioned here. There are two factors in fishes which strongly influence the immune response and antibody production, seasonal changes and temperature. The main lymphoid organs are described here: the thymus, the kidney and the spleen, as well as the lymphocyte ontogenic process. Some advances in knowledge were published during the last years, however it is still necessary to develop new studies in basic immunology in different species to caracterize effector cell populations and their functions.La función esencial del sistema inmune en todos los vertebrados es la defensa contra las infecciones. Los peces presentan una respuesta inmunológica bien desarrollada e integrada, y en el caso de los Teleósteos, con algunas similitudes respecto a los vertebrados superiores. Puede ser dividido en dos tipos: innato o inespecífico y adquirido o específico, ambos compuestos por una parte humoral y celular. Su importancia puede variar con la edad del pez y está influenciada por distintos factores. Se mencionan aquí sus componentes más relevantes. En los peces existen dos factores que influencian notoriamente la respuesta inmune y la producción de anticuerpos, que son los cambios estacionales y la temperatura. Se describen los principales órganos linfoides, el timo, el riñón y el bazo, así como el proceso ontogénico linfocitario. Si bien se ha avanzado mucho en los últimos años, todavía se necesitan estudios de inmunología básica en las distintas especies que ayuden a caracterizar las poblaciones efectoras y sus mecanismos de acción

Immunomodulatory action of manganese superoxide dismutase (Mn-SOD) in juvenile American white shrimp (Litopenaeus vannamei) was studied. Shrimp between 0.7 and 1.0 g were immersed in aerated β-glucan, lipopolysaccharide (LPS), fucoidan, and heat-killed Vibrio penaeicida solutions for 6 h. The enzymatic activity of Mn-SOD in entire organisms was investigated to evaluate whether different immunostimulants were able to induce antioxidant activity. The immunostimulants tested activated the immune system in juvenile shrimp and the highest antioxidant response was observed 48 h after the challenge with β-glucan, LPS, fucoidan and heat-killed V. penaeicida. The bacterin caused 3.2 times more Mn-SOD activity than the control group. Immunostimulated shrimp were challenged with live V. penaeicida on the tenth day and a second antioxidant response was observed 48 h after exposure to live pathogenic bacteria. Immunostimulated shrimp with β-glucan showed the highest Mn-SOD response (2.5 times more than the control group). This study showed the capacity of juvenile shrimp to enhance antioxidant response during a challenge with pathogenic bacteria after exposure to immunostimulants.