Effect of dietary chitosan on the growth, survival, and prophenoloxidase of male freshwater prawns Cryphiops (Cryphiops) caementarius

This research aimed to evaluate the effect of dietary chitosan on the growth, survival, and prophenoloxidase of male freshwater prawns Cryphiops (Cryphiops) caementarius. Seventy-two prawns were acclimated and allocated into four dietary treatments: a control group and three experimental diets supplemented with 1, 2, and 4 g chitosan/kg of diet. Growth parameters were similar (P > 0.05) among dietary treatments with a higher weight gain (21%) observed in the 2 g of chitosan/kg diet. Prawns' survival (55–72%) was similar (P > 0.05) among dietary treatments, although it was biased by deaths caused by incomplete ecdysis syndrome. The highest prophenoloxidase levels in hemocytes (66.28%) were those from the prawns fed on 1 g of chitosan/kg of diet. On the other hand, hemocytes with lower prophenoloxidase content (12.52% and 19.36%) were observed in prawns fed on 2 and 4 g of chitosan/kg of diet, respectively, however it is likely that their prophenoloxidase levels were negatively affected by the high concentration of nitrites (≥ 0.33 mg/L) detected in the culture water. This study is the first to demonstrate that low concentrations of chitosan in the diet of C. (C.) caementarius increase prophenoloxidase levels and thus it could be used in the aquaculture practice of this resource to stimulate its immune system.