Effects of Unleaded Petroleum on the Macrophage Aggregates (MA) formation in Red King tilapia (Oreochromis sp.) Fingerlings

The Philippines is one of the major producers of tilapia, the most cultured fish and widely consumed in the world. Although fishes in general is said to be adapted to various stressful conditions, the effect on several cellular immune parameters may be of interest to determine the capacity of the organism to withstand stressors. In this paper, the effect of unleaded petroleum on the splenic macrophage aggregate (MA) formation was studied. This was done to have an overview of the immune response of Tilapia or fishes in general when an oil spill, which almost occur annually at different parts of the world, happen. Histological analysis assessed the area occupied by splenic MA 24 hours after introduction of unleaded petroleum to the aquatic system. To determine whether Mabuhay balls, a technology that claims to be beneficial in terms of improving water quality, was added to one tank (T1) to be able to compare it with another tank (T2). There is a strong statistically significant difference between the groups at day1 (p=0.000) opposite the result of day 6 (p=0.155). Thus, unleaded petroleum increased MA formation, a sign that may indicate a high immune activity as an initial positive response to stress. Mabuhay ball have lessen the mortality but has no effect on splenic MA formation.