Some Forms of Gill Disease in Penaeid Shrimp

Gill disease in penaeid shrimp is a complex of several afflictions, any of which may result in death of affected animals either by outright destruction of the gills or by suffocation resulting from mechanical blockage of gas exchange across the surface of the gill lamellae. Organisms demonstrated to cause gill disease in penaeids include an imperfect fungus that belongs to the genus Fusarium, at least two types of epicommensal peritrichs that belong to the genera Zoothamnium and Lagenophrys, and a filamentous bacterium that superficially resembles Leucothrix mucor. “Black gills” or melanization of the gill process is a sign of several forms of gill disease and is not a disease in itself. “Black gills” occur in shrimp with heavy infestations of Lagenophrys. “Black gills” are not usually seen in animals that have heavy infestations on the surface of the gills of either the epicommensal peritrich Zoothamnium or the filamentous bacterium. Detritus and algae are often trapped by these epicommensals, and this results in gills that range in color from green to dark brown. Demonstrable histological damage to the gills does not occur in shrimp dying from heavy infestations of the filamentous bacterium or Zoothamnium. Histopathological changes are readily demonstrated in animals having Fusarium infections and in animals with the epicommensal Lagenophrys sp.