LUMINOUS BACTERIAL DISEASE IN TIGER SHRIMP POST-LARVAE (PENAEIIS MONODON FABRICIUS) IN A HATCHERY NEAR VISAKHAPATNAMN. ARAVINDAN AND C. SHEEJA
The cause of mass mortality in Penaeus monoo'on post-larvae in a hatchery at Thimmapuram, near Visakhapatnam was inves(igated. Luminous bacteria associated with exoskeleton, gills and gut were isolated, identified and quantified. Their abundance and distribution profiles were studied. Attempts were made to evaluate the optimal threshold level of luminous bacterial concentration in ambient water to initiate luminescence disease. Studies were also made to assess the lethal concentration (Lc) of luminous bacteria in hepatopancreas to enhance 50% mortality. Results of the biochemical characterization analysis revealed Vibrio harveyi as disease causing agent. In addition, gut of the host was found to support high density of V. harveyi than gills and exoskeleton. Results on Lcso experiments showed 50% mortality of P. monodon post-larvae with luminous bacterial concentration of 5.7 x 106 nos./m1 at 43 hrs. Post-larvae challenged with low levels bacterial concentrations in water did not exhibit luminescence disease. However, higher bacterial concentration, 4.66 x 106 nos./ml to 122.33 x 106 nos./m1 (acute) showed luminescence and other clinical signs of luminous Vibriosis.
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