ABSTRACT
This chapter discusses a very few of thousands of toxicants now present in natural waters. The gills of a fish constitute a multifunctional organ (respiration, ionoregulation, acid-base regulation, nitrogenous waste excretion) accounting for well over 50 percent of the total surface area of the animal. The branchial epithelium is made up of multiple cell types and is both delicate and geometrically complex. Mallatt has provided a comprehensive and quantitative synthesis of more than 100 toxicologic studies in which structural changes in the gills were examined by light or electron microscopy. The chapter provides an alarming conclusion that is how little we know at present about toxicant action at the gills of seawater fish in contrast to freshwater fish, despite the fact that species abundance, fish productivity, and economic importance are all so much greater in the marine environment.
