Agriculture Reference
In-Depth Information
any material or equipment of high cost. Further details of this test are described by Kihlman
(1975).
Fig. 3.
Tradescantia pallida
. (Photo: Guilherme Thiago Maziviero)
4. Biomarkers
Molecular, biochemical and physiological compensatory mechanisms can become operative
in organisms after exposure to environmental contaminants. This may result in the
inhibition or facilitation of one or more physiological mechanisms or functional and
structural changes. In this sense, the use of biomarkers allows obtaining information about
the biological effects of pollutants and mechanisms of action of xenobiotics on the fauna.
Several authors have proposed different definition for the term biomarkers. According to
Lam and Gray (2003), biomarkers can be defined as biochemical, cellular or molecular
alterations or physiological changes in the cells, body fluids, tissues or organs of an
organism that are indicative of exposure or effect of a xenobiotic. Despite being older, the
definition proposed by Depledge (1993) and Depledge et al. (1993) has a more
comprehensive character and it is considered the most widely used nowadays: biomarkers
are defined as adaptive biological responses to stressors, evidenced as biochemical, cellular,
histological, physiological or behavioural alterations.
In the scope of measuring the toxic effects in the organisms at a cellular or molecular level,
biomarkers represent an initial response to environmental disturbances and contamination.
Therefore, they are generally considered more sensitive than the tests that measure these
effects at higher levels of biological hierarchy, such as individual or population (McCarthy
& Shugart, 1990).
Thus, during the last decades, several biomarkers have been used effectively, especially as
tests for specific toxicants, since biomarkers when combined with biomonitors can create a
sophisticated multiple target system to detect a variety of environmental hazards in a fast
and economically feasible way, in a single test organism, helping in the establishment of
priorities for action in the control of environmental pollution.
4.1 Morphological biomarkers
The detection of many classes of damage in several tissues and cellular types becomes
possible by using morphological biomarkers. Such morphological alterations may provide
qualitative evidences of a functional adaptation to the external environment (Meyers &
Hendricks, 1985). Moreover, the qualitative assessment of such changes before the death of
the organism may provide early indications of toxicity (Nogarol & Fontanetti, 2010;
Triebskorn et al., 1999).
