Identification of haematological markers in shrimp health assessment from the immune profile of Fenneropenaeus indicus on β-1,3-glucan administration and white spot syndrome virus challenge

Abstract

Haematological alterations in Fenneropenaeus indicus fed marine yeast glucan-incorporated diet and challenged with white spot syndrome virus were analysed. Adult F. indicus 16.45 ± 2.12 g (mean ± SD) were reared in 25 ‰ sea water and allowed to acclimate for a period of 7 days. Diet was prepared incorporating glucan (0.2 %) extracted from marine yeast, Debaryomyces hansenii S169. The shrimps were reared on experimental diet for 28 days and then challenged with white spot syndrome virus through oral administration. Random sampling was done (n = 6 shrimps) on 1st, 15th and 28th day of the experiment and on post-challenge day 2 (PCD 2) and PCD 7 for haematological analysis. The immune parameters viz. plasma protein, total haemocyte count, phenoloxidase activity, superoxide anion production, alkaline phosphatase and acid phosphatase activities were estimated in the haemolymph. Superoxide dismutase, catalase, glutathione peroxidase, hydroperoxide, conjugated dienes and malondialdehyde concentrations in the haemolymph of shrimps were also analysed. Analysis of variance showed that there are significant differences (p < 0.05) in the immune and antioxidant parameters in different treatment groups of F. indicus. The shrimps fed glucan-incorporated diet showed higher survival rate with comparatively lower accumulation of lipid peroxidation products. Correlation coefficients showed that all haematological variables except hydroperoxides and conjugated dienes exhibited positive correlation with the survival rate. The immune variables and antioxidant parameters exhibited a greater degree of correlation with each other. When multiple regression of survival rate on all immune parameters was considered, the amount of variability explained was 93 % (R Square = 0.932). When significant regression coefficients among the immune parameters were taken into account, it was found that total haemocyte count (p < 0.001), phenoloxidase activity (p < 0.05), alkaline phosphatase activity (p < 0.05) and plasma protein concentration (p < 0.05) together are explaining 84 % (R 2 = 0.842) of the variability, indicating that these four parameters are mainly supporting the survival. The amount of variability explained by the antioxidant parameters was 94 % (R 2 = 0.938). When significant regression coefficients among the antioxidant parameters were taken into account, it was found that superoxide dismutase activity (p < 0.01) and catalase activity (p < 0.05) together are explaining 87.4 % (R 2 = 0.874) of the variability, indicating that these two antioxidants act as the major immune effectors supporting the survival in shrimps.