Histopathologic biomarkers
Histopathologic alterations in fish tissues are biomarkers of effect of exposure to environmental stressors. This category of biomarkers has the advantage of allowing one to examine specific target organs and cells as they are affected under in vivo conditions. Furthermore, for field assessment, histopathology is the most rapid method of detecting adverse acute and chronic effects of exposure in the various tissues and organs comprising an individual finfish or shellfish. Although very numerous, environmental pollutants act through a finite number of ultimately toxic mechanisms to produce a finite number of histopathologic lesions. While only broad generalizations regarding the specific etiologic agent(s) responsible for such lesions can be made, the ability to determine the magnitude of toxic impairment strengthens efforts to predict eventual impact on the survival of the affected individual and, in some instances, the population. Confounding issues for histopathologic biomarkers include distinguishing changes caused by anthropogenic toxicants from those due to infectious disease, normal physiologic variation, or natural toxins. In this chapter, we emphasize the use of biomarkers of toxicant-induced histopathologic change and attempt to distinguish these lesions from those caused by 156other etiologies. We limited present biomarkers (those ready for immediate use) to reliable, well-documented lesions, based on experience to date, in liver, ovary, musculoskeletal system, and skin. Other, potential or future biomarkers are also identified. These lesions may have strong field relevance but lack laboratory toxicologic support data, or they may have been seen in the laboratory but not in the field. We also describe an additional complement of research tools, available to the experimental pathologist, which may provide even more meaningful biomarkers. These powerful, integrative, laboratory-proven approaches correlate structural with biochemical and physiological alteration and yield quantitative endpoints amenable to statistical analysis. Many, however, lack field verification. The chapter also details the proper application of histopathologic biomarkers, identifies research needs to increase sensitivity and use of these approaches, and presents approaches for collection of biota, which increase precision of analysis and interpretation of results.
