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pollutants, in freshwater or marine waters, are still rare in the literature. Crossing of
individuals from contaminated systems can produce F1 and F2 generations that display
a resistance to pollutants similar to the one observed for their parents; thus, this toler-
ance can be considered a genetic adaptation of the population (Belfiore and Anderson
2001; Johnston 2011).
Using this approach, Klerks and Moreau (2001) investigated the potential resistance of
the fish
Cyprinodon variegatus
to chemical stress under experimental conditions; they high-
lighted a decreasing heritability of resistance to chemical stress with the growing number
of pollutants in the mixture. For this fish species, the complexity of the mixture consider-
ably reduced the possibility of resistance or slowed down the development of this adapta-
tion. On the other hand, artificial selection carried out in the laboratory on another fish
(
Heterandria formosa
)
showed a fast response to cadmium selection; after only one genera-
tion of selection, a proportion of two selected lineages out of three displayed an increasing
resistance to cadmium (Xie and Klerks 2003).
After the remediation of a site highly contaminated by cadmium, a complete and a
rapid loss (between 9 and 18 generations) of genetically based cadmium resistance was
observed for a population of a freshwater oligochaete
Limnodrilus hoffmeisteri
; this result
was linked to the dominance of one pollutant and to a probable selective pressure on one
locus (Levinton et al. 2003).
Several studies have underlined that
F. heteroclitus
populations from three chronically
polluted estuarine systems in the United States are resistant to the aromatic hydrocarbons
in their environment, as compared to nearby fish from relatively clean habitats; resistance
in first- and sometimes second-generation embryos suggests that differential survival
could be due to genetic adaptation rather than to physiological acclimation (synthesis in
Burnett et al. 2007; Van Veld and Nacci 2008).
Recent work has also been conducted on the effects of multigenerational exposure
to pollutants on arthropods. The long-term effects of nine trace metals were studied in
insect larvae, those of the midges
Chironomus plumosus
and
Culicoides furens
; the sen-
sitivity to trace metals decreased with LC
50
values becoming larger between first and
third generations (Vedamanikam and Shazilli 2008).
Daphnia magna
were exposed to a
pesticide mixture consisting of a pyrethroid insecticide and a pre-emergent herbicide,
and significant differences were detected between F0 and F1
D. magna
for survival, in
which F1 waterfleas were less sensitive to pesticide mixtures than F0 (Brausch and Salice
2011).
14.4.3 Cost of Resistance to Toxicants
The energy allocated by an organism to stress resistance increases its survival probabil-
ity, but will reduce the energy allocated to essential functions such as growth or repro-
duction, perhaps significantly. Trade-offs are widely detected in the literature between
maintenance (survival) and production (measured by developmental rate, fecundity, etc.),
particularly in stressed populations (Mouneyrac et al. 2011).
In their synthesis on the cost of tolerance to toxins measured in experimental approaches,
Van Straalen and Hoffman (2000) underlined the cost of tolerance to metals for plants,
invertebrates, and fishes, generally identified by a very low frequency of tolerant individu-
als in “pristine” conditions and by different alterations of life history traits. Arthropods
resistant to insecticides also displayed a cost that is characterized in “pristine” habitats
by a loss of physiological performance in terms of fecundity, developmental rate, and
fertility (Roush and McKenzie 1987). The resistance of the mosquito
Culex pipiens
to
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