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HISTOPATHOLOGICAL BIOMARKERS AS INTEGRATORS OF ANTHROPOGENIC AND ENVIRONMENTAL STRESSORS
Citation:
Myers, M. S. AND J W. Fournie. HISTOPATHOLOGICAL BIOMARKERS AS INTEGRATORS OF ANTHROPOGENIC AND ENVIRONMENTAL STRESSORS. Chapter 2, S. Marshall Adams (ed.), Bioindicators of Stress in Aquatic Organisms. Wiley and Sons, Boca Raton, FL, , 221-287, (2002).
Description:
Histopathology is an extremely useful tool for assessing effects of exposure to stressors at the level of the individual. Even though the histopathological approach is somewhat qualitative, it is very valuable because the observed lesions represent an integration of cumulative effects of biochemical and physiological changes as well as representing actual injury to the organism. This approach also allows identification of specific cells, tissues, and organs that have been affected. We have presented information in the chapter on a number of lesions in various tissues and organs that may at some point in time have the potential as reliable histopathological biomarkers of specific environmental stressors, but require further validation by epidemiological and laboratory studies. Examples include lesions of the excretory kidney, gonad, gills, central nervous system, neurosensory organs, and hemopoietic tissues in head kidney. In our opinion, there are only a small number of histopathological biomarkers that have been shown via rigorous epidemiological methods and experimental validation to be reliable indicators of exposure to various stressors. These include liver lesions, splenic macrophage aggregates, some skin lesions, and certain musculoskeletal abnormalities. Some are relatively specific while others are more nonspecific, and all require the investigator to account for seasonal, physiological, age and sex-related variation. For example, an epizootic of liver neoplasms and other liver lesions involved in the stepwise histogenesis of liver neoplasia in a population of fish indicates that they have been exposed to hepatotoxic and pepatocarcinogenic contaminants. Elevated numbers of splenic macrophage aggregates is a less specific indicator, but still indicates that the affected fish probably have been exposed to contaminated sediments, low dissolved oxygen, or some other stressor. Because histopathology is a biologically meaningful method of evaluating the effects of stressors on animals, it should be an essential component of all environmental assessments. In order to assess the health status of a body of water it is necessary to evaluate the health of the organisms inhabiting the particular body of water, which requires a histopathological examination of representative tissues and organs from those organisms.