Page 23 - The Toxicology of Fishes

1

Introduction

Richard T. Di Giulio and David E. Hinton

Toxicology, the study of the adverse effects of chemicals, has a rich history, the bulk of which revolves
around understanding the effects of poisons on humans. Michael Gallo (2001) provided an excellent
and lively historical perspective on human health-oriented toxicology, including historical and literary
examples of inquiry from antiquity, the Middle Ages, and the Age of Enlightenment. As he noted,
modern toxicology draws upon many fields of basic science; these include molecular biology, chemistry
and biochemistry, genetics, organismal biology, ecology, and mathematics. Indeed, the solution to most
important toxicological questions requires interdisciplinary approaches drawing on multiple forms of
expertise. A distinction that has been used to categorize toxicology is biomedical vs. environmental
(or ecotoxicology), the former focusing on human health and the latter on free-living flora and fauna
and their populations, communities, and supporting ecosystems. The latter is a relatively young field,
at least in the sense of a formal science; the term ecotoxicology was first used by Truhaut in 1969
(Truhaut, 1977) and is often used to stress the fate and effects of chemicals within an ecosystem
(Kendall et al., 2001).
Ecotoxicology has been defined in various ways, but for most of us it means the study of effects that
chemical pollutants exert on natural biota. Contributing to the biocomplexity that we are challenged
with is the large number of species for which meaningful data are needed. To deal with effects at various
levels of biological organization and in a large number of organisms, we must extrapolate findings
between species. It should also be noted, however, that some definitions are broadened to include effects
on any biosphere component, including humans (Newman and Unger, 2003), and increasing consider-
ation for integrative connections between human health and the well-being of natural systems appears
to be enhancing interactions between the fields of biomedical toxicology and ecotoxicology (Di Giulio
and Benson, 2002) and also integrations of risk assessments for human health and ecosystem protection
(Munns et al., 2003; Suter et al., 2003).
Fish occupy a prominent position in the field of toxicology; they have been employed amply in studies
concerning both human and ecological health, probably bridging this divide more than any other class
of organisms. Several reasons likely account for this. Fish are by far the most diverse class of vertebrates;
the 28,000 species identified to date are greater than the combined numbers for the other classes (Cossins
and Crawford, 2005). This taxonomic diversity is reflected in a diversity of body forms, lifestyles, and
physiologies, which also reflect the great diversity of aquatic systems that fish inhabit, from freshwater
to hypersaline waters, with temperatures ranging from below freezing to >45°C, pressures ranging from
1 to 1000 Atm, and other variabilities in solar radiation, oxygen concentrations, ionic and organic matter
compositions, turbulence, bottom environments, and so forth. This species and habitat diversity has long
driven the use of fishes for scientific inquiries into the influences of environmental variables on the
evolution, genetics, and adaptations of organisms.
In the context of pollution, aquatic systems are highly vulnerable due to their tendency to accumulate
relatively high concentrations of chemicals entering from surrounding terrestrial systems, as well from
direct inputs; thus, regardless of their source of entry to the environment, aquatic systems are oftentimes
repositories for a large array of stressor chemicals (for example, see Chapters 2 and 14 in this volume).

3