Evaluation of immuno-biochemical attributes of Asian green lipped mussel (Perna viridis) and characterization of selected immune related gene

Abstract

This study entitled ‘Evaluation of immuno- biochemical attributes of Asian green lipped mussel (Perna viridis) and characterization of selected immune related gene’ mainly aimed to analyze the seasonal impacts on biochemical and immunological parameters in the haemolymph and mantle fluid of Perna viridis and to characterize an immune related gene (ferritin) in Perna viridis. Perna viridis (Linnaeus, 1758) is one of the economically important marine bivalves which has also been recognized as an ideal aquatic animal for bio-monitoring. Being a filter feeder organism, haemocytes and soluble haemolymph factors of this mussel contributed effectively in their defense strategy and survival. Further, deviations from these basal values can be used to predict various stressful conditions. Yet, use of such attributes for monitoring of marine pollutants is rarely attempted. The present study provides seasonal baseline data of 11 relevant haemolymph and mantle fluid parameters to predict the eco-immunological status of apparently healthy, P. viridis. The entire sampling was done three times a year which is based on average temperature and average precipitation, coinciding the spawning season. Relevant immune-biochemical parameters for the haemolymph as well as mantle fluid such as total haemocyte count (THC), superoxide anion generation (SO), phenol oxidase activity (PO), lysozyme activity, glucose content, total protein, albumin, cholesterol, triacylglyceride and were also evaluated for each samples. Condition index evaluated for each season showed an increasing trend in the first two seasons indicating somatic growth, and for other seasons, it was appeared to be comparable. Total bacterial counts peaked in summer season. Lysozyme and albumin were found beyond detection level in the present study. Haemolymph Superoxide anion production showed a decreasing trend among seasons, while it reached maximum at the monsoon season for mantle fluid. Phenoloxidase activity was highest in the monsoon season for haemolymph and mantle fluid. No significant difference (P<0.05) was observed in THC and glucose levels of haemolymph between three seasons. However, mantle fluid glucose showed a peak in summer season. Conversely, no significant difference in haemolymph protein level was observed between the first two seasons, where it differed significantly among seasons for mantle fluid. Circannual trend for haemolymph cholesterol showed a steep decrease in first two season where triacylglyceride indicated an opposite pattern. Conversely, both showed similar pattern in mantle fluid. A reproduction-immunity trade-off is observed for protein, cholesterol and triglyceride in haemolymph with lower value observed for spawning season. However, none of the parameters studied showed a consistent significant correlation pattern (P<0.001) with respect to season. Further investigations are required to pave light on the seasonal dynamics of metabolic interaction and their immune outcome through interlinking of these attributes to tissues and body fluids with their active transport in P. viridis. Ferritin, a principal protein found in the cells of almost all living organisms for iron storage and immune responses have rarely been reported in mussels, and to our knowledge ferritin gene is not yet fully characterized in P. viridis. So this study also aimed to characterize the ferritin gene in Asian green lipped mussel. The full length cDNA of ferritin gene was found to be 798 bp with a deduced amino acid of 173. It has a Euk_Ferritin domain with three conserved residues- ferroxidase diiron center, ferrihydrite nucleation center and iron ion channel. This result may serve as a reference for further studies regarding the expression of this gene. Thus, the outcome of the study can be exploited in various pollution monitoring studies and disease management strategies for P. viridis culture.