Page 730 - The Toxicology of Fishes

710 The Toxicology of Fishes

Chemical exposure

Chemical bioavailability

Chemical–ligand binding

Cellular metabolism

Biochemical dysfunction

Physiological dysfunction

Apoptosis Necrosis Biochemical adaptation

Physiologic adaptation DNA adduct
(mutation)

Cell and tissue
morphologic adaptation

Whole-animal death Whole-animal adaptation Neoplasia
FIGURE 16.6 Cascade of histopathological alterations as result of biochemical and physiological alterations in an organ-
ism. (Adapted from Hinton, D.E. and Laurén, D.J., in Biological Indicators of Stress in Fish, Vol. VIII, Adams, S.M., Ed.,
American Fisheries Society, Bethesda, MD, 1990, pp. 51–66; Hinton, D.E. et al., in Biomarkers: Biochemical, Physiological,
and Histological Markers of Anthropogenic Stress, Huggett, R.J. et al., Eds., Lewis Publishers, Boca Raton, FL, 1992, pp.
155–209.)

contamination of aquatic ecosystems was first suggested by Dawe et al. (1964), who postulated that
liver neoplasms observed in white sucker and brown bullhead from Deep Creek Lake in Maryland might
have resulted from chemical exposure. Since that time, numerous wild fish tumor epizootics have been
identified in North America alone, dominated by liver tumors in bottom feeders in the vicinity where
chemical contaminants were concentrated. Pierce et al. (1978), for example, reported the occurrence of
hepatic tumors in English sole in Puget Sound in Washington. Malins et al. (1984) also studied sediment-
associated chemicals from near-coastal areas and related PAHs to the induction of tumors in marine fish
species. A good correlation, in fact, was found between the indices of hepatocellular carcinoma or
papilloma of the fish examined and PAH sediment concentration. Likewise, Black (1983) reported that
a high prevalence of epidermal papilloma, epidermal carcinoma, and hepatocellular carcinoma was
observed in brown bullhead inhabiting the Buffalo River, in which sediment was contaminated with
PAHs. Harshbarger et al. (1993), and Moore and Myers (1994) provided additional fish histology
references focused on the pathobiology of chemical-associated neoplasia in aquatic organisms.
Morphological change can manifest itself in various external and internal lesions or diseases that can
be easily quantified (Au, 2004). External metrics include fin erosion, skeletal abnormalities, epidermal
hyperplasias, and opercular abnormalities (Au, 2004). In addition, a number of characteristics of ana-
tomical and cytological alterations favor the use of histological examination in the biomarker approach
(Myers and Fournie, 2002). With a thorough prior knowledge of normal anatomy, the use of histological
analysis can be used to detect chemically induced alterations in a variety of tissues and organs in many