Effect of air exposure on the immune system of the rock lobster Panulirus cygnus

Abstract

This study aimed to determine the effect of post harvest operations such as air exposure on the health status of lobsters. These effects can be assessed through measurement of selected immune parameters such as total haemocyte counts, haemolymph clotting time, bacteraemia and the differential proportion of granular cells in lobster haemolymph. Lobsters were taken from factory holding tanks and exposed to air for 2, 6, 12, and 18 h through placement in foam boxes. Controls were sampled at each time point by collecting lobsters from the same tank as the experimental animals (10 animals /treatment group) with a different group of lobsters being sampled at each time point. Air exposure caused a significant increase in clotting time at 12h and 18h. Total haemocyte counts showed a decreasing trend. The proportion of granular cells tended to be lower in air-exposed animals, the difference was significant at 2h exposure. The bacteraemia levels tended to be higher in air exposed lobsters than in controls and the difference was significant at 12h exposure. Low total haemocyte counts, high clotting times, low granular cell numbers and high bacteraemia levels implied increased susceptibility to infection and lowered immunity. The results show that air exposure has a significant adverse effect on the immune system and hence on the health status of the lobsters.