Evaluation of some hemato-immunological parameters in the shrimp Farfantepenaeus paulensis submitted to environmental and physiological stress

Abstract

The modulation of some immunological and/or physiological parameters, as a response to stressful conditions, may function as an important indicator of health status especially in cultivated animals such as shrimps, where a rapid and precise assessment of health conditions is crucial to ensure the success of culture programs. In this study, we investigated the alteration of some hemato-immunological parameters in the shrimp Farfantepenaeus paulensis after exposure to one of the following stressful conditions: (a) low salinity (22‰ and 13‰), (b) unilateral eyestalk ablation in females and (c) spermatophore extirpation in males. The investigated parameters were: the total hemocyte count (THC), total serum protein concentration (PC), phenoloxidase (PO) activity and agglutinating activity of the serum. At low salinity, the shrimp hemograms (THC) were systematically lower (up to 40% in shrimps maintained for 2 weeks at a salinity of 13‰) than in control animals (47,312±5510 cells/mm 3). Also, in destalked females and spermatophore-extirpated males, the THC was 56.3% and 63% lower, respectively, than that of control animals (52,159±12,692 cells/mm 3 for females, 48,241±5236 cells/mm 3 for males). Similarly, PC was approximately 50% lower in destalked females and spermatophore-extirpated males, when compared with control shrimps (125±23 mg/ml for females, 151±16.6 mg/ml for males). On the other hand, the PC of shrimps maintained in low salinity did not show such a pronounced decrease. The specific PO activity, after trypsin treatment, increased significantly in the serum of spermatophore-extirpated males (43.3±4.2 and 26.5±2.1 U/min/mg in extirpated and control males, respectively), but not in destalked females. On the other hand, a clear correlation between PO activity and water salinity was not observed in this study. Interestingly, PO activity (total and specific) markedly decreased in all tested salinities in the last 2 weeks, suggesting a partial suppression of the prophenoloxidase (proPO) system probably due to the stress caused by captivity. The agglutinating activity of F. paulensis serum against sheep erythrocytes was extremely variable, even within treatments, and there was no apparent correlation with the stress agents. Among the investigated hemato-immunological parameters, THC and PC were the most sensitive parameters to stress conditions and could be virtually incorporated in shrimp cultivation programs, following technique standardization.