Bio-augmentation of heterotrophic bacteria in biofloc system improves growth, survival, and immunity of Indian white shrimp Penaeus indicus.

Effect of bio-augmentation of Bacillus spp in biofloc on growth, survival and immunity in Indian white shrimp Penaeus indicus was evaluated. Nine Bacillus strains were isolated and screened individually as well as in the form of a consortia. To maintain a C:N ratio of 12:1 a blend of carbohydrate sources was used. Bio-augmentation with bacterial consortium and Virgibacillus sp. produced improved growth and immunity. Shrimp survival ranged from 80 to 95% among treatments. Production was higher (35%) in the biofloc tanks with an average body weight (ABW) of 10.89 ± 1.2 g. On evaluating the immune responses, it was found that trypsin significantly (P < 0.05) enhanced Prophenoloxidase (PO) activity in Lysinibacillus, Bacillus cereus, Bacillus licheniformis and Bacillus subtilis bio-augmented groups. Laminarin induced PO activity was observed in groups supplemented with Oceanobacillus sp., Bacillus sp.and Bacillus megaterium. The lysozyme (LZ) activity was significantly (P < 0.05) higher in B. cereus and Microbial Consortia (MC), while other treatments were less effective. Total hemocyte count (THC) significantly (P < 0.05) increased in all treatment groups compared to the control. Hyaline hemocyte (HH) count was significantly (P < 0.05) higher in the control group (14.43%). Semi granular hemocytes (SGH) was higher in groups treated with Lysinibacillus, Bacillus sp., B. licheniformis and B. subtilis. The granular hemocyte (GH) count was significantly (P < 0.05) higher in Virgibacillus sp., B. cereus, B.megaterium and Oceanobacillus sp. The biofloc alone (BF), treated and augmented with B. megaterium significantly (P < 0.05) increased phagocytic activity. Highly significant phagocytic index (PI) was observed in bio-augmented groups, BF and MC. The relative expression levels of immune genes were found to be significantly up-regulated in shrimps grown in bio-augmented groups. Enhanced immunological parameters implies that bio-augmentation of biofloc with Bacillus spp. improved immunity in shrimps. Hence, bio-augmentation of probiotics in biofloc may be useful in improving culture conditions to produce P. indicus.

First record of Cymothoa indica (Crustacea, Isopoda, Cymothoidae) infecting the cultured catfish Mystus gulio in India.

Cymothoa indica (Isopoda, Cymothoidae) is reported parasitizing the long-whiskered catfish Mystus gulio, cultured in an experimental cage in India. The specimens observed were adult males and females, which had mainly settled in the buccal cavity of juvenile catfish. The species was previously known from wild populations of Siganidae and Belonidae, but this is the first record of C. indica parasitizing the cultured long-whiskered catfish. Serious lesions, typical of a crustacean infection, were macroscopically visible inside the buccal cavity. The cumulative mortality, over a period of 10 d, was 100%. The parasitic problem was not successfully dealt with, due to an unexpected prevalence and very swift mortality.