Toxicological pathology in laboratory fish: an evaluation with two species and various environmental contaminants.

: This paper presents an overview of the studies carried out in small laboratory fish species to investigate the usefulness of histopathology as a tool in aquatic toxicology. The studies were performed with medaka (Oryzias latipes) and guppy (Poecilia reticulata) that were exposed to a variety of environmental contaminants for one and three months. Besides the measurement of routine toxicological parameters, total body histopathology was carried out. The data are summarized and evaluated in view of their contribution to the knowledge of toxicology, the specific responsiveness of animals and tissues, and the application in ecotoxicology. It is concluded that histopathology of (small) fish exposed to environmental contaminants may provide useful information as to target organs and mechanism of action: moreover, this technique can be more sensitive than routine parameters.