Impairments of Endocrine Functions: Case Studies - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 235

Moreover, fish with high plasma VTG would have a significantly reduced fertility (Nash
et al. 2004).
Occurrence of EDCs may affect hormone synthesis. P450 aromatase catalyzes the con-
version of C19 androgens to C18 estrogens, which is thought to be essential for the regula-
tion of the reproductive function. Measurements of aromatiase activity (AA) in polluted
sites showed that activity is significantly up-regulated in sites with fish showing high lev-
els of plasma VTG concentration, thus suggesting the occurrence of estrogenic compounds
and their involvement in AA modulation (Geraudie et al. 2011). Furthermore, a significant
decrease in plasma estradiol (50-60%) and 11-ketotestosterone (76-84%) was measured,
indicating that EDCs may have interfered with the normal sex steroid synthesis of male
roaches (Geraudie et al. 2010b).
9.2.5 Fish Feminization and Other Consequences
The most obvious endocrine disrupting effect in fish is the occurrence of intersex fish liv-
ing in the Seine estuary (Minier et al. 2000a, b). These intersex fish have testes, generating
not only spermatozoa but also oocytes. Histological sections thus show, among a generally
normal male tissue, some typically female cells including primary and secondary oocytes
(Figure 9.11). However, histological examinations of gonads through a sexual cycle show
that the intersex fish generally cannot ensure a full and normal development of second-
ary oocytes. They do not become eggs and degenerate prematurely. The cells must be
eliminated and thus represent a waste of reproductive potential and a significant energy
expenditure that might be harmful. It is important to note that such intersex fish can be
generated experimentally by exposing fish to EDCs during a crucial window of develop-
ment, thus showing the involvement of these compounds, including steroids, in the phe-
nomenon (Baroiller and D'Cotta 2001). Some treatments may even completely reverse the
sex of the organism. What is particularly revealing about the extent of the effects in the
Seine estuary is that many species are affected. Intersex individuals were observed in
OO
M
50 µm
FIGURE 9.11
Histological section of testis of flounder ( Platichthys flesus) ) showing occurrence of degenerating primary oocytes
(OO) in male tissue (M).