ABSTRACT
In aquatic toxicology, the functional anatomy of fishes and the presence of organ pathologies has informed us about the modes of action of toxic substances. However, a similar understanding has yet to emerge for engineered nanomaterials (ENMs). This chapter uses a target organ approach to identify the pathologies that have been associated with the body systems of fish. The focus is exclusively on in vivo exposures and the pathologies that develop in vivo. Exposure to high concentrations of ENMs can compromise the integrity of external barriers such as the gut and the gills of fish. All of the major body systems and most of internal organs show evidence of pathology from in vivo exposures. Injuries include fatty change in the liver, the presence of necrotic cells in the renal tubules, melanomacrophage deposits in the spleen and degeneration of the skeletal muscle fibres. There is also evidence of indirect brain pathology, most likely arising from vascular injury and/or systemic hypoxia. Unequivocal demonstration of brain pathology from ENMs inside the matter of the brain is yet to be demonstrated in vivo. However, some effects on sense organs, and changes in behaviour due to altered sensory perception have been observed. Only a few seemingly nano-specific pathologies have been found. Most pathologies are also known for traditional chemicals, although the aetiology is often different for the nano form. There are many data gaps, with the information limited to a few species of fish and mostly pristine ENMs.
