Protein and DNA Content in the Gills of Labeo rohita During Aeromoniasis

Aeromonas liquefaciens is one of the most important pathogen of warm water fish. Aeromoniasis is associated with tail and fin rot, hemorrhagic septicemia, exopthalmus, plae gills etc. It is a serious disease causing heavy damage in Indian Major carp culture. A wide genetic variation in resistance has been noted in Labeo rohita for aerononiasis. The present investigations are designed to estimate the content of protein and DNA from gills of fish experimentally infected with various doses of A. liquefaciens. Four groups (66 fish in each group) of fish were given infection intramuscularly @ 10-2 CFU/fish (group A), 10-4 CFU/fish (group B), 10-5 CFU/fish (group C), and 10-6 CFU/fish (group D). Another four groups of fish (a, b, c, and d) (66 in each group) were kept as uninfected controls for comparison. Six fish from groups A, B, C and D and a, b, c and d were necropsied, tissues of gill were separated and analyzed for protein and DNA content at hour 1, 3, 6, 12, 18, 24, 36, 48, 72, 96, and 216 and for histopathological changes on hour 24 of experimental period. Marked increase of protein in gill was found at hour 6 and 72 in group A, at hour 1, 18, 24 and 36 in group C and at hour 1 to 216 in group D when compared with controls. A peak level of protein was found at hour 3, 6 and 12 in fish received 10-6 CFU/fish (group D) when compared with other experimental groups. The decrease in the content of DNA during later period of infection (from hour 12 to 216) in experimental groups of A and B (which received higher doses) may reflect the depressed oxidative respiration, due to infective bacterial pathogen exposure. Fish received small doses showed much disturbed oxidative respiration under infection gills of experimental fish showed enlargement of lamellae and loss of secondary lamellae (in groups A and B) and atrophy of primary lamellae and curling and clubbing of secondary lamellae (in groups C and D) exposure. Varied degrees of response were observed to various degrees of pathogenic doses in fish with regard to protein and DNA content.