Effect of marine plant (Excoecaria agallocha) extract against luminescence disease causing Vibrio harveyi during shrimp larviculture

Abstract

Crude extract of Excoecaria agallocha was tested for antagonism against Vibrio harveyi and an inhibitory zone of 9.9 ± 0.4 mm was observed. When V. harveyi was grown in Luria Bertani (LB) agar with crude extract of plant, the growth of microorganisms decreased from 2.946 to 1.782 OD in 5 days. In control, V. harveyi growth increased from 3.290 to 3.592 OD. When V. harveyi was treated with the plant extract, proteolysis, lipolysis, phospholipase and thermonuclease activity and bio-luminescence was weak. Similarly, crude bacteriocin OD values showed a decreasing trend from 1.937 to 1.452 OD as compared to the control from 2.073 to 1.739 OD. The disruption of protease production ranged from 0.010 to 0.121. Exopolysaccharide production of V. harveyi decreased from 2.791 to 2.691 OD as compared to the control (3.387 to 3.23 OD). The reduction in the cumulative percentage mortalities in the treatment tank was 4 to 14 % due to the addition of crude extract of E. agallocha when compared to the control. The results suggested that the crude extract of E. agallocha can be used as a non-antibiotic agent to control shrimp disease caused by V. harveyi