Morphologic evaluation of the gills as a tool in the diagnostics of pathological conditions in fish and pollution in the aquatic environment: a review

Abstract

Fish gills, owing to their status as a multifunctional organ, have always fascinated researchers. In spite of the intense work done on the morphologic examination of gills, the organ is relatively under-used in health evaluation in fish. The existing literature on this topic is reviewed here. Our review summarises important diagnostic guidelines for the examination of gill structure and describes the morphological lesions that develop under the influence of different biological and physicochemical factors. The picture that should emerge is that of an organ that is extremely sensitive to all types of handling and unfavourable changes in the external and internal environments. We conclude that studying the morphology of the fish gills provides an opportunity to assess fish health status as well as information on possible health hazards coming from their environment.