Some
parasites are expected to have beneficial impacts on wild
populations in polluted environments because of their bioaccumulation
potential of pollutants from their hosts. The fate of organic micropollutants
in host–parasite systems and the combined effect of parasitism
and pollution were investigated in chub Squalius cephalus, a freshwater fish, infected (n = 73) or uninfected
(n = 45) by acanthocephalan parasites Pomphorhynchus sp. from differently contaminated
riverine sites. Several ubiquitous pollutants (polychlorinated biphenyls
(PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl-ethers
(PBDEs), polycyclic aromatic hydrocarbons (PAHs), phthalates, insecticides,
pyrethroids, and N,N-diethyl-meta-toluamide
(DEET)) and some of their metabolites were characterized for the first
time in parasites and various fish matrices (muscle, liver, and stomach
content). Most organic pollutants reached higher levels in parasites
than in chub matrices. In contrast, metabolite levels were lower in
parasite tissues compared to fish matrices. Infected and uninfected
chub exhibited no significant differences in their pollutant load.
Body condition, organo-somatic indices, and immunity were not affected
by parasitism, and few correlations were found with chemical pollution.
Interestingly, infected chub exhibited lower oxidative damage compared
to uninfected fish, irrespective of their pollutant load. In light
of these results, this correlative study supports the hypothesis that
acanthocephalan parasites could bring benefits to their hosts to cope
with organic pollution.
Polycylic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in the marine environment. Their toxicity is mainly linked to the ability of marine species to biotransform them into reactive metabolites. PAHs are thus often detected at trace levels in animal tissues. For biomonitoring purposes, this findings have two main consequences, (i) the determination of the PAH tissue concentration is not suitable for the evaluation of individual exposure to PAHs (ii) it can explain sometimes the lack of correlations obtained with relevant markers of toxicity such as genotoxicity biomarkers. The aim of the present study was to better investigate the link between PAH exposure and genotoxicity in marine flatfish. During a laboratory experiment, juvenile soles were exposed for four weeks to a mixture of three PAHs, namely benzo[a]pyrene, fluoranthene and pyrene, followed by one week of depuration. Fish were exposed via the trophic route to a daily PAH concentration of 120 μg/g food. Fish were sampled at different time points. The bioavailability and the biotransformation of PAHs were assessed by the measurement of biliary metabolites using a sensitive UPLC MS/MS method. The 7-ethoxyresorufine-O-deethylase was also measured in liver subcellular fractions as a biomarker of phase I biotransformation activities. Genotoxicity was assessed in parallel by the measurement of DNA strand breaks in fish erythrocytes by the alkaline comet assay. During this study, the high amount of PAH metabolites produced in sole demonstrated the bioavailability of PAHs and their biotransformation by fish enzymes. A positive correlation was observed between the level of hydroxylated PAH metabolites and genotoxicity as measured by the alkaline comet assay.
The embryonic development of the sea bass Dicentrarchus labrax during the endotrophic period is discussed. An 8 cells stage, not reported for other studied species, results from two rapid successive cleavages. Blastula occurs at the eighth division when the embryo is made of 128 cells. During gastrulation, the infolded blastoderm creates the endomesoblastic layer. The Kupffer's vesicle is reported to drive the left/right patterning of brain, heart and digestive tract. Heart formation starts at 8 pairs of somites, differentiation of myotomes and sclerotomes starts at the stage 18 pairs of somites; main parts of the digestive tract are entirely formed at 25 pairs of somites. At 28 pairs of somites, a rectal region is detected, however, the digestive tube is closed at both ends, the jaw appears the fourth day after hatching, but the mouth is not opened before the fifth day. Although cardiac beating and blood circulation are observed, gills are not reported in newly hatched individuals; eye melanization appears concomitant with exotrophic behavior.
Trophic magnification factors (TMFs, i.e. the average change in the log-concentration of a pollutant per trophic level) have been extensively assessed for the so-called persistent organic pollutants, especially organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), which are biomagnified along the food web. In contrast, trophic dilution was documented for pollutants with a high metabolic transformation rate, such as phthalate plasticizers and PAHs (Polycyclic Aromatic Hydrocarbons). However, the fate of their metabolites across the food web has been rarely investigated. In this comparative study, the trophodynamics of 104 micropollutants and 25 of their metabolites were investigated in a freshwater food web from the urban Orge River, France. Trophic levels were determined using stable isotopes. Pyrethroid pesticides and their metabolites were not detected. As predicted, PCBs and OCPs biomagnified (TMF > 1), while all chlorinated paraffins (CPs), PAHs and phthalates underwent a trophic dilution (TMF < 1). TMFs significantly decreased with metabolic transformation rate and increased with hydrophobicity. The levels of PAH or phthalate metabolites were not significantly correlated to trophic levels or underwent a trophic dilution. This study highlighted that the relative contribution of metabolite levels in TMF values calculated for both parent compound and its metabolite(s) is weak compared to TMF values of the parent compound only in a riverine food web.
Data regarding the link between DNA integrity of germ cells and the quality of progeny in fish exposed to genotoxicant are scarce although such information is of value to understand genotoxic effects of contaminants in aquatic fauna. This work aimed at studying the consequences of a parental exposure during the breeding season on offspring quality in three-spined stickleback. After in vivo exposure of adult fish to methyl methane sulfonate, a model alkylating compound, a clear increase in DNA damage was observed in erythrocytes of both genders, here used as a biomarker of exposure. MMS exposure significantly affected sperm DNA integrity but neither female fecundity nor fertilization success. In order to understand the contribution of each sex to potential deleterious effects in progeny due to parental exposure, mating of males and females exposed or not to MMS, was carried out. Exposure of both males and females or of males alone led to a significant increase in both mortality during embryo-larval stages and abnormality rate at hatching that appeared to be sensitive stages. Thus, in accordance with recent studies carried out in other freshwater fish species, such development defects in progeny were clearly driven by male genome, known to be devoid of DNA repair capacity in spermatozoa. The next step will be to investigate the link between DNA damage in stickleback sperm and reproductive impairment in natural populations exposed to complex mixture of genotoxicants.
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