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fish from both reference and contaminated sites. On the other hand, the finding of specific
lesions only in fish from contaminated sites suggested a contaminant etiology, particularly
when they were similar to those observed in laboratory exposures to specific contami-
nants (Teh et al. 1997).
Assessment of liver tissues was carried out in the sharptooth catfish
Clarias gariepinus
from
two dams in South Africa known to be multipolluted (metals, endocrine disrupting chemi-
cals) despite being situated within a protected urban nature reserve (Marchand et al. 2008).
Histopathological alterations included structural alterations in 27% of studied specimens,
granular or fatty degeneration of hepatocytes (98% and 25%, respectively), hepatocyte nuclear
alterations (90%), an increase in melanophage centers (32%), and necrosis of liver tissue (14%).
By using a standardized quantification of histopathological alterations, the authors were able
to distinguish between the degrees of impact at these two sites (Marchand et al. 2009). In
the same species, Abdel-Moneim and Abdel-Mohsen (2010) examined the ultrastructural
changes in hepatocytes of specimens from a polluted location and a relatively clean area in
Lake Mariut, Egypt. Fish hepatocytes from the polluted area showed accumulation of hetero-
chromatin, enlarged nucleoli, and an extremely folded nuclear envelope. The most frequent
pathological modifications were the swelling of mitochondria and cristae regression.
4.4
Conclusions
The use of cortisol impairment as a biomarker, however conceptually attractive, presents
considerable difficulties. Hontela (2000) stresses the need for “very specific sampling pro-
tocols since several factors influence cortisol secretion,” first of all the stress of capture and
handling. In addition to this problem of feasibility, conflicting results have been shown in
the present review of the literature. In a review encompassing many more species than
aquatic organisms, Busch and Hayward (2009) highlight a steep increase in the number of
conservation-related field studies that measure glucocorticoid hormones (corticosterone or
cortisol) as markers for stress. Since glucocorticoids have key roles in vital functions (ani-
mal performance including growth and metabolism, fetal development), it may be argued
that, in addition to being able to reveal the presence of chemical stressors, cortisol is a bio-
marker with added ecological value as described for arctic fish and polar bears (Letcher et
al. 2010). Despite a great potential for informing conservation, interpretation of the results
of endocrine tools is often complicated.
AChE activity proved to be a responsive biomarker in different biological models, with
decreased values at sites influenced by agricultural, urban, and industrial activities. This
is well recognized for environmental assessment in monitoring programs (Burgeot et al.
2010). It is not as specific for OP and carbamate pesticides as was initially believed, but this
inconvenience may be turned to advantage, since AChE activity can be used as a generalist
biomarker, representative of the physiological status of organisms (Leiniö and Lehtonen
2005). Different forms of ChE exist in invertebrates and fish, and they can exhibit variable
susceptibility to environmental contaminants. However, in many studies, it is unclear if
the authors have truly characterized the enzyme that they call AChE. A better fundamen-
tal knowledge of this biomarker would help in correctly interpreting field data.
It is also important to be aware of all confounding factors capable of modulating the
response of AChE activity in the presence of neurotoxicants. However, it seems that the
problem may be more or less crucial, depending on the biological model used for AChE
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