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Abstract:
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Influence of acute salinity stress on the immunological and physiological response of Penaeus monodon to white spot
syndrome virus (WSSV) infection was analysed. P. monodon maintained at 15‰ were subjected to acute salinity changes to 0‰
and 35‰ in 7 h and then challenged orally with WSSV. Immune variables viz., total haemocyte count, phenol oxidase activity
(PO), nitroblue tetrazolium salt (NBT) reduction, alkaline phosphatase activity (ALP), acid phosphatase activity (ACP) and
metabolic variables viz., total protein, total carbohydrates, total free amino acids (TFAA), total lipids, glucose and cholesterol were
determined soon after salinity change and on post challenge days 2 (PCD2) and 5 (PCD5). Acute salinity change induced an
increase in metabolic variables in shrimps at 35‰ except TFAA. Immune variables reduced significantly (Pb0.05) in shrimps
subjected to salinity stress with the exception of ALP and PO at 35‰ and the reduction was found to be more at 0‰. Better
performance of metabolic and immune variables in general could be observed in shrimps maintained at 15‰ that showed
significantly higher post challenge survival following infection compared to those under salinity stress. Stress was found to be
higher in shrimps subjected to salinity change to lower level (0‰) than to higher level (35‰) as being evidenced by the better
immune response and survival at 35‰. THC (Pb0.001), ALP (Pb0.01) and PO (Pb0.05) that together explained a greater
percentage of variability in survival rate, could be proposed as the most potential health indicators in shrimp haemolymph. It can be
concluded from the study that acute salinity stress induces alterations in the haemolymph metabolic and immune variables of
P. monodon affecting the immunocompetence and increasing susceptibility to WSSV, particularly at low salinity stress conditions |