Evaluation of some hemato-immunological parameters in female shrimp Litopenaeus vannamei submitted to unilateral eyestalk ablation in association with a diet supplemented with superdoses of ascorbic acid as a form of immunostimulation

The main purpose of this study was to examine the modulation of some hemato-immunological parameters in female shrimp L. vannamei submitted to unilateral eyestalk ablation and whose diet was supplemented with superdoses of vitamin C, as a form of immunostimulation. The analyzed parameters were: total hemocyte counts (THC), protein concentration (PC), agglutinating and phenoloxidase (PO) activities in the serum, and levels of glucose and lactate in the plasma. Broodstock shrimp females were analyzed on the day before ablation and on days 1, 3, 7 and 14 after ablation. The diet was supplemented with superdoses of vitamin C, in the form l -ascorbyl-2-polyphosphate (ApP). The females were divided into a control group (NS), not supplemented with superdoses of ApP, and two other groups (S1 and S2) supplemented with doses 10 and 20 times the recommended dose of 200 mg/kg, respectively. Surprisingly, the great majority of the hemato-immunological parameters analyzed did not exhibit any statistically significant change in relation to eyestalk ablation in NS group. There was only a significant reduction in the agglutinating activity on the third day following ablation. Similarly, in S1 and S2 groups, there were no significant changes in the majority of the parameters analyzed, except for the agglutinating titre and the level of glucose in the plasma. However, unlike the NS group, S1 and S2 did not exhibit a decrease in the agglutinating activity on the third day after ablation. This could possibly suggest a potential immunostimulation in this parameter by vitamin C. The S1 and S2 groups were hypoglycemic on the first day after ablation. This hypoglycemia probably resulted from a transitory decrease in the levels of the hyperglycemic hormone as a consequence of eyestalk ablation and removal of the X-organ-sinus gland. The absence of significant changes in the hemato-immunological parameters in unilaterally ablated L. vannamei females suggests the existence of a compensatory mechanism induced by the non-ablated eyestalk. It can be further speculated that the hemato-immunological parameters selected in this study were not the most appropriate for the evaluation of this stress condition or, possibly, that L. vannamei is a highly resistant species capable of maintaining homeostasis, even when subjected to the severe physiological and mechanical stress of eyestalk ablation.