Cloning and Expression Analysis of Keratin 18 Gene in Loach(Misgurnus anguillicaudatus) Incidence of antioxidant enzymes and vitellogenin induced in male loach (Misgurnus anguillicaudatus) exposed to octylphenol The effects of different methods of cultivation on the densities of Brachionus calyciflorus(rotifer)and its environmental conditions