Relationship between DNA damage in sperm after ex vivo exposure and abnormal embryo development in the progeny of the three-spined stickleback

Leachate from Weathered Face Masks Increases DNA Damage to Sperm of Sand Dollars Scaphechinus mirabilis

The COVID-19 pandemic has exacerbated the problem of environmental contamination of disposable personal protective equipment, in particular face masks (FMs). As a result of environmental factors, FMs undergo aging and fragmentation processes and become a source of microplastics (MPs) and chemical additives. Taking into account the scale of accumulation of used FMs and their fragments in the coastal zone, it should be expected that the most appreciable ecotoxicological consequences should be observed in hydrobionts inhabiting coastal ecosystems. Based on this, the aim of this study was to investigate the toxicity of leachates from pristine and weathered FMs using sperm of sand dollars Scaphechinus mirabilis. In our work, we used pristine and weathered FMs, which for 200 days were kept in the external environment under natural conditions and exposed to a complex of climatic factors. Fourier transform infrared spectroscopy was used to characterize the chemical changes that occurred in the polymer structure of FMs during this period. It follows from the results obtained that leachates from pristine and weathered FMs reduced sperm viability; stimulated the accumulation of lipid peroxidation products, such as malondialdehyde (MDA); and significantly increased the destruction of DNA molecules, showing a genotoxic effect. Overall, our results complement the limited experimental data presented, indicating the genotoxic properties of face mask extracts.

In vitro assessment of the genotoxicity and immunotoxicity of treated and untreated municipal effluents and receiving waters in freshwater organisms

Municipal wastewater effluent is one of the largest sources of pollution entering surface waters in the Laurentian Great Lakes. Exposure to wastewater effluent has been associated with impaired immune systems and induction of genotoxicity to aquatic animals. Due to habitat degradation and environmental pollution linked to industrial development and population growth, several regions of the Great Lakes have been designated Areas of Concern (AOCs). In this study, we assessed the effect of extracts of sewage influent, (treated) effluent and receiving surface waters from the Hamilton Harbour AOC and the Toronto and Region AOC (Ontario, Canada) on the phagocytic immune response of rainbow trout (Oncorhynchus mykiss) kidney leukocytes and the genotoxicity (DNA strand breaks) of these extracts on freshwater mussel (Eurynia dilatata) hemocytes. We identified and quantified numerous chemicals present in the various samples extracted for exposure. In freshwater mussels, extracts from Hamilton Harbour AOC induced DNA damage with the most frequency (12 out of 28 samples) regardless of sample type, reflecting past and present industrial activities. In contrast, extracts from Toronto and Region AOC induced DNA damage infrequently (2 out of 32 (summer) and 5 out of 32 (fall) samples, respectively) and from different WWTPs at different times. None of the extracts induced any significant effect on phagocytosis of rainbow trout kidney leukocytes. The present study indicates that despite overall improvements to effluent quality, treatment of influent by WWTPs may not result in a corresponding improvement of the genotoxicity of effluents. In vitro bioassays are useful and cost-effective rapid-screening tools for preliminary assessments of contamination of aquatic ecosystems.

DNA repair genes play a variety of roles in the development of fish embryos

Embryogenesis is one of the most important life stages because it determines an organism's healthy growth. However, embryos of externally fertilizing species, such as most fish, are directly exposed to the environment during development and may be threatened by DNA damaging factors (pollutants, UV, reactive oxygen species). To counteract the negative effects of DNA fragmentation, fish embryos evolved complex damage response pathways. DNA repair pathways have been extensively studied in some fish species, such as zebrafish (Danio rerio). Our literature review, on the other hand, revealed a paucity of knowledge about DNA damage response and repair in non-model aquaculture fish species. Further, several pieces of evidence underlie the additional role of DNA repair genes and proteins in organogenesis, spatiotemporal localization in different tissue, and its indispensability for normal embryo development. In this review, we will summarize features of different DNA repair pathways in course of fish embryo development. We describe how the expression of DNA repair genes and proteins is regulated during development, their organogenetic roles, and how the expression of DNA repair genes changes in response to genotoxic stress. This will aid in addressing the link between genotoxic stress and embryo phenotype. Furthermore, available data indicate that embryos can repair damaged DNA, but the effects of early-life stress may manifest later in life as behavioral changes, neoplasia, or neurodegeneration. Overall, we conclude that more research on DNA repair in fish embryos is needed.

Genotoxic Effects of Exposure to Water-Soluble Fraction of Diesel Fuel in Sand Dollar Scaphechinus mirabilis Gametes

Pollution of marine areas with oil and oil products is steadily growing. As part of this connection, the study of the impact of petroleum hydrocarbons on marine hydrobionts is an urgent issue of modern ecotoxicology. In our study, the genotoxic effect of the water-soluble fraction of diesel fuel at different concentrations on the gametes of the sand dollar Scaphechinus mirabilis was evaluated. It was shown that during the incubation of sperm and eggs of a sand dollar in WAF with an oil hydrocarbon content of 1.32; 2.64; 5.37; 7.92 mg/L caused the destruction of the DNA molecule to varying degrees in both types of gametes. In addition, it has been shown that with an increase in the concentration of petroleum hydrocarbons in WAF, a large number of cells with a high level of DNA damage appear. The success of fertilization after exposure of gametes to a water-soluble extract of petroleum hydrocarbons was also evaluated. The relationship between an increase in the concentration of hydrocarbons in the tested solutions and a decrease in the level of fertilization is shown.

Aroclor 1254 impairs sperm quality, fertilization ability, and embryo development of rainbow trout (Oncorhynchus mykiss)

The polychlorinated biphenyls (PCBs) in aquatic environment adversely affect non-target organisms, including fish. Especially, the male reproduction and next generation can be damaged through high exposure to these pollutants. Hence, the sperm cells were exposed to sublethal concentrations of Aroclor 1254 (0, 1, 5, 10, or 25 mg/l) for 4 h. The sperm quality parameters were analyzed by SCA (Sperm Class Analyzer). The fertility, eyeing, and hatching rates were determined as gamete markers. Lipid peroxidation (malondialdehyde-MDA), glutathione (GSH), and antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT)] were measured for determination of oxidative stress. Our results showed that Aroclor 1254 negatively affected the motility rate and duration, fertilization rate, embryogenesis, and hatching and also triggered antioxidant defense mechanisms at the highest concentration (25 mg L^-1). Furthermore, linear speed (VSL), linearity index (LIN), and amplitude lateral head (ALH) were significantly changed after exposure to 25 mg L^-1, and the lowest concentrations (1 and 10 mg L^-1) did not significantly affect the motility and fertilizing capacity. The embryogenesis and hatching were significantly affected by sperm exposure to 1, 10, and 25 mg L^-1 of Aroclor 1254. Consequently, Aroclor 1254 causes potential hazards in male germ cells, and the exposure of sperm cells to pollutants can adversely affect next generation of wild populations.

Zinc Oxide Nanoparticles Induce DNA Damage in Sand Dollar Scaphechinus mirabilis Sperm

Products containing nanomaterials are becoming more and more common in everyday life. Zinc oxide nanoparticles (ZnO NPs), meanwhile, are among the most widely used NPs. However, their genotoxic effect on the germ products of marine organisms is poorly understood. Therefore, the effects of ZnO NPs and zinc ions (20, 50, 100, 200 µg/L) on the sperm of sand dollar Scaphechinus mirabilis were compared. Comet assay showed that both tested pollutants caused an increase in DNA damage to 6.57 ± 2.41 and 7.42 ± 0.88% DNA in the comet tail, for zinc ions and ZnO NPs, respectively. Additionally, a different pattern was shown by the increase in DNA damage, with increasing concentration of pollutants, in different experimental groups.

Transcriptome and Proteome Analyses Reveal Stage-Specific DNA Damage Response in Embryos of Sturgeon (Acipenser ruthenus)

DNA damage during early life stages may have a negative effect on embryo development, inducing mortality and malformations that have long-lasting effects during adult life. Therefore, in the current study, we analyzed the effect of DNA damage induced by genotoxicants (camptothecin (CPT) and olaparib) at different stages of embryo development. The survival, DNA fragmentation, transcriptome, and proteome of the endangered sturgeon Acipenser ruthenus were analyzed. Sturgeons are non-model fish species that can provide new insights into the DNA damage response and embryo development. The transcriptomic and proteomic patterns changed significantly after exposure to genotoxicants in a stage-dependent manner. The results of this study indicate a correlation between phenotype formation and changes in transcriptomic and proteomic profiles. CPT and olaparib downregulated oxidative phosphorylation and metabolic pathways, and upregulated pathways involved in nucleotide excision repair, base excision repair, and homologous recombination. We observed the upregulated expression of zona pellucida sperm-binding proteins in all treatment groups, as well as the upregulation of several glycolytic enzymes. The analysis of gene expression revealed several markers of DNA damage response and adaptive stress response, which could be applied in toxicological studies on fish embryos. This study is the first complex analysis of the DNA damage response in endangered sturgeons.

The impact of time and environmental factors on the mitochondrial vesicle and subsequent motility of amphibian sperm

For amphibian species that display external fertilization in an aquatic environment, hypoosmotic shock to sperm cells can quickly result in damage to cellular structure and function. This study sought to determine how fertilization media osmolality, temperature, and time impact the stability of the mitochondrial vesicle's association with the sperm head and thus motility and quality of forward progression. The presence of the mitochondrial vesicle and its relationship with sperm motility and quality of forward progression were analyzed in sperm samples from the Fowler's toad (Anaxyrus fowleri) (n = 10) when held for six hours under two temperatures and four osmolalities. Results indicated that the presence of the mitochondrial vesicle is needed for sperm motility over time (p < 0.001), where higher osmolalities (p < 0.001) and lower temperatures (p < 0.001) correlated with maintaining the vesicle attachment to the spermatozoa. The higher osmolality of spermic urine was the most important factor for maintaining higher quality of forward progressive motility (p < 0.01) of spermatozoa. Sperm samples held at 4 °C and 40 mOsm/kg had the longest half-life for motility (540 min) and quality of forward progression (276 min), whereas sperm held at 22 °C and 2.5 mOsm/kg had the shortest half-life for motility (7 min) and quality of forward progression (18 min). Special attention should be given to the osmolality and temperature of fertilization solutions, or breeding tank water, when developing cold storage protocols for toad sperm or reproducing animals to ensure the retention of the mitochondrial vesicle for maximum fertilization capability.

Ascorbic acid ameliorated the sperm quality of rainbow trout (Oncorhynchus mykiss) against arsenic toxicity: Impact on oxidative stress, fertility ability and embryo development

Arsenic (As) is a heavy metal and aquatic pollutant and adversely impacts the reproduction of male fish. As a chain-breaking antioxidant, ascorbic acid (AA) has high water solubility and low toxicity. In this context, the current study was performed to assess the protective role of AA (1 mM) on the sperm cells of the rainbow trout (Oncorhynchus mykiss) exposed to sublethal concentrations of As (8, 16 and 32 mg/L). Sperm quality parameters were analyzed using a sperm class analyzer system. Lipid peroxidation and antioxidant enzyme levels were used as indicators of oxidative stress. The fertilization, eyeing and hatching rates were determined as gamete markers. Reduced sperm quality parameters and fertility capacity resulted from in vitro exposure to As (P < 0.05). The oxidative stress in sperm cells increased after As exposure (P < 0.05). The presence of AA improved sperm movement parameters and fertility potential (P < 0.05). Overall, AA had a positive effect on oxidative stress and fertility ability against As toxicity and AA supplementation ameliorated detrimental effects of As in sperm cells.

Genotoxicity of Polystyrene (PS) Microspheres in Short-Term Exposure to Gametes of the Sand Dollar Scaphechinus mirabilis (Agassiz, 1864) (Echinodermata, Echinoidea)

Microplastic pollution appears to be one of the major environmental problems in the world today, and researchers have been paying special attention to the study of the impact of microplastics on biota. In this article, we studied the short-term effects of polystyrene micro-spheres on genome integrity using the gametes of the Scaphechinus mirabilis sand dollar with the comet assay method. This highly sensitive method allowed us to identify the level of genome damage in both gametes before and after short-term exposure to PS microparticles. It was shown that primary polystyrene microspheres at concentrations of 104, 105, and 106 particles/L had a genotoxic effect during short-term exposure to the sperm of the sand dollar S. mirabilis, which was expressed as a significant increase in sperm DNA damage. The highest percentage of DNA damage (more than 20%) was detected in spermatozoa exposed for 1 h in water containing 105 microspheres of plastic per 1 L. Additionally, at all concentrations of microplastic studied in the experiment, the genetic damage index (GDI) values in spermatozoa exceeded the control level. However, regardless of the level of DNA damage, spermatozoa retained the ability to fertilise eggs with up to 97% efficiency. We must acknowledge that the genotoxic property of microplastic against sperm to some extent predicts the development of long-term adverse effects of environmental significance.

Toxic effects of ZnSe/ZnS quantum dots on the reproduction and genotoxiticy of rare minnow (Gobiocypris rarus)

ZnSe/ZnS quantum dots (QDs) have excellent optical properties, but researchers have not clearly determined whether they cause harm to organisms. In the present study, the effect of ZnSe/ZnS QDs on the parents and offspring of rare minnow were evaluated for the first time. Exposure to ZnSe/ZnS QDs altered the testicular structure, caused sperm DNA damage and decreased sperm motility in males. They also suppressed the expression of reproduction-related genes, such as androgen receptor (Ar), DM-related transcription factor 1 (Dmrt1), estrogen receptor (Er), and X-ray repair cross complementing gene 1 (Xrcc1). Continued monitoring of the F1 generation revealed that the embryonic development of the F1 generation was abnormal and the growth index of the F1 generation of adult fish showed hormesis. A comet assay showed that the F1 generation still had DNA damage in the 400 and 800 nmol/L groups at 96 h post-fertilization (hpf). Thus, ZnSe/ZnS QDs damaged the reproductive system of the rare minnow, and this effect continued to the F1 generation.

De novo cytogenetic alterations in spermatozoa of subfertile males might be due to genome instability associated with idiopathic male infertility: Experimental evidences and Review of the literature

Male infertility is caused by many factors including genetics. Although part of genetic damages are inherited and could be traced in blood leukocytes, but those de novo alterations induced in spermatogenesis are not part of diagnostic work up. De novo alterations might be the cause of many idiopathic conditions of male infertility. The aim of this study was to evaluate DNA damage, sex chromosomal aneuploidy and DAZ microdeletion in sperms of subfertile males in comparison with normal healthy individuals. Whole blood and semen samples were obtained from 75 subfertile and 45 normal men. Semen samples from karyotypically normal subfertile and normal individuals were used for DNA fragmentation, sex chromosome aneuploidy and DAZ microdeletion analysis. Sperm DNA damage was assessed by alkaline comet assay, chromosome aneuploidy and DAZ microdeletion was assessed using a combined primed in situ labeling and fluorescent in situ hybridization (PRINS-FISH) method. A significantly high percentage of DNA fragmentation was observed in subfertile patients compared to control. Similar observation was observed for sex chromosome aneuploidy and DAZ microdeletion (p < 0.01). A relatively small interindividual difference was seen in all three assays performed. However DAZ microdeletion was observed as mosaic form in Y bearing sperms. Results indicate that subfertile males experience higher genome instability in spermatogenesis expressed as DNA damage and consequently sperm chromosomal 220 AIMS Genetics Volume 3, Issue 4, 219-238. aneuploidy or microdeletions. Occurrence of de novo genetic alterations caused by environmental chemico-physical genotoxic agents during spermatogenesis might be one of the causes of idiopathic male infertility.

Oxidative Stress and DNA Damage of Zebrafish Sperm at Different Stages of the Cryopreservation Process

Although gamete cryopreservation has facilitated advancement of reproduction research by allowing the storage of cells over prolonged periods of time, during freezing-thawing cycles, cells inevitably suffer from cryoinjuries. Here, we evaluate oxidative stress and DNA damage of zebrafish sperm at different stages of the cryopreservation process. It was generally observed that the freezing and thawing of the samples led to an increase in the generation of reactive oxygen species and the activity of the catalase enzyme and a reduction in the generation of sulfhydryl groups and superoxide dismutase activity. The alkaline comet assay demonstrated that DNA damage increased after equilibration time, with an even greater increase after freezing and thawing. The comet assay modified with the enzyme formamidopyrimidine glycosylase, and Endonuclease III demonstrated greater DNA damage than the standard comet assay, demonstrating a high degree of oxidation of purines and pyrimidines at all stages of cryopreservation. Our results show that the freeze and thaw processes cause greater oxidative stress and DNA damage than cryoprotectant toxicity during exposure at the equilibrium stage.

Semen parameters on the intracytoplasmic sperm injection day: Predictive values and cutoff thresholds of success

OBJECTIVE

This study was conducted to investigate the relationship of semen parameters in samples used for intracytoplasmic sperm injection (ICSI) with fertilization and pregnancy rates in infertile couples.

METHODS

In this prospective study of Infertile couples with male factor infertility that had undergone ICSI, fractions of the same semen samples obtained for microinjection (to ensure the best predictability) were evaluated to determine the semen parameters and sperm DNA fragmentation index (DFI) on the day of oocyte recovery.

RESULTS

In total, 120 couples completed the study and were subdivided into fertilized (n=87) and non-fertilized couples (n=33). The fertilized couples were further classified into pregnant (n=48) and non-pregnant (n=39) couples. Compared to non-fertilized and non-pregnant couples, fertilized and pregnant couples showed statistically significantly higher sperm viability and percentage of normal sperm morphology, as well as significantly lower sperm DFI values. A receiver operating characteristic curve analysis of data from the 120 ICSI cycles showed that sperm viability, normal sperm morphology percentages, and sperm DFI were significant prognostic indicators of fertilization at cutoff values of 40%, 7%, and 46%, respectively. A sperm DFI of 46% showed sensitivity and specificity of 95% and 90%, respectively, for predicting fertilization, and no clinical pregnancies occurred in couples with a sperm DFI above 46%.

CONCLUSION

Semen parameters from the ICSI day sample, especially sperm viability, normal morphology, and DFI, had an impact on fertilization and pregnancy outcomes in ICSI cycles.

DNA of crayfish spermatozoa as a target of waterborne pesticides - An ex vivo approach as a tool to short-term spermiotoxicity screening

The spermiotoxic properties of aquatic contaminants might be the cause of low fertilization rate and decreased prolificacy, affecting the success of the impacted populations. The genotoxic potential of pesticides in spermatozoa as an undesirable effect on non-target organisms, namely aquatic invertebrates with external fertilization, emerges as a key question in ecogenotoxicological research. Thus, this study aimed to clarify if DNA integrity of red swamp crayfish (Procambarus clarkii) spermatozoa is affected by waterborne pesticides at environmentally relevant concentrations. By adopting an ex vivo approach, six pesticides were addressed in a short-term assay: herbicides glyphosate (9 and 90 μg L^-1) and penoxsulam (2.3 and 23 μg L^-1); insecticides dimethoate (2.4 and 24 μg L^-1) and imidacloprid (13.1 and 131 μg L^-1); fungicides pyrimethanil (2.2 and 22 μg L^-1) and imazalil (16 and 160 μg L^-1). Genotoxicity was observed in higher concentrations of glyphosate, penoxsulam, dimethoate, pyrimethanil, and imazalil. Imidacloprid was the only pesticide that did not cause non-specific DNA damage, although displaying pro-oxidant properties. Overall, the present study demonstrated the suitability of the ex vivo approach on spermiotoxicity screening, highlighting the potential ecological impact of pesticides on non-target species, such as P. clarkii, compromising sperm DNA integrity and, subsequently, the population success.

Biomarkers as tools for monitoring within the Water Framework Directive context: concept, opinions and advancement of expertise

The Water Framework Directive (WFD) currently supports chemical and ecological monitoring programmes in order to achieve the good water surface status. Although chemical and ecological assessments are necessary, they have some limitations. Chemical approaches focus on certain substances identified as priorities, but they do not take into account other potentially harmful substances and also ignore the hazards related to contaminant cocktails. On the other hand, while ecological approaches provide holistic information on the impairment of biological communities in ecosystems, they do not distinguish the role of contaminants in these alterations, and consequently do not allow the establishment of contaminant impact reduction plans. Consequently, ecotoxicologists suggest the use of effect-based tools such as biomarkers. Biomarkers highlight the effect of potentially harmful substances (or a cocktail), and their specificity towards the chemicals makes it possible to properly discriminate the role of toxicants within biological community impairments. Thus, the integration of such tools (besides existing chemical and ecological tools) in the WFD could considerably improve its biomonitoring strategy. The B n' B project (Biomarkers and Biodiversity) exposes key objectives that will allow to (i) establish an inventory of the biomarkers developed by French laboratories; (ii) determine their methodological advancement and limits and, on this basis, formulate recommendations for biomonitoring use and future research needs; (iii) discuss the biomarkers' ecological significance, specificity to contaminants and interpretation capacity; (iv) establish, in fine, a selection of valuable biomarkers to enter the WFD; and (iv) propose integrative tools to facilitate the decision-taking by stakeholders.

The effect of sperm DNA fragmentation index on assisted reproductive technology outcomes and its relationship with semen parameters and lifestyle

Background

The sperm DNA fragmentation index (DFI) is widely regarded as a key measure for assessing male fertility, but the predictive value of the DFI for outcomes of assisted reproductive technology (ART) remains under debate. In this study, we used a large sample to analyze the effect of sperm DFI on pregnancy outcomes following ART and its relationship with oocyte fertilization and embryo development in in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). We also explore the value of sperm DNA fragmentation (SDF) and its associated factors in assessing male fertility.

Methods

The relationship between the DFI measured with the sperm chromatin structure assay (SCSA) and pregnancy outcomes following ART were retrospectively analyzed in 2,622 ART treatment cycles, of which 1,185 were intrauterine insemination (IUI) cycles, 1,221 were IVF cycles and 216 were ICSI cycles. Rates of pregnancy, early abortion, oocyte fertilization and good quality embryos from IVF and ICSI cycles were compared between the groups of low DFI (DFI ≤15%), medium DFI (15%< DFI <30%) and high DFI (DFI ≥30%). Additionally, the relationships between sperm DFI and male lifestyle variables such as age, body mass index, smoking, and alcohol consumption, as well as routine semen parameters, were analyzed.

Results

Clinical pregnancy rates following IUI among high, medium, and low sperm DFI groups were 12.5% (11/88), 14.3% (48/336), and 13.4% (102/761), respectively, with no statistical difference between the groups (P=0.88); however, early abortion rates among these groups were 27.3% (3/11), 14.6% (7/48), and 4.9% (5/102), respectively, and the difference was statistically significant (P=0.02). No significant differences in the rates of clinical pregnancy, early abortion, oocyte fertilization, or good quality embryos in IVF or ICSI cycles were detected among different DFI groups (P<0.05). Sperm DFI was negatively associated with sperm density, vitality and normal morphology; It was positively correlated with age, abstinence time and unhealthy lifestyles.

Conclusions

As an increasingly common technique for reproductive testing, sperm DFI has proven to be very valuable in male fertility evaluation, but its significance as a predictor of pregnancy outcomes following ART requires further investigation.

Effects of a chronic exposure to different water temperatures and/or to an environmental cadmium concentration on the reproduction of the threespine stickleback (Gasterosteus aculeatus)

Knowledge about combined effects of chemicals and temperature on reproductive capacity of fish are rare in literature, especially when it comes to the effects of chronic low-dose chemical exposure combined to the thermal stress. The aim of the study was to evaluate the single and combined effects of temperature (16, 18, 21 °C) and an environmentally relevant concentration of waterborne cadmium (1 µg L^-1, nominal concentration) on the reproductive outputs of threespine stickleback (Gasterosteus aculeatus), and their consequences on offspring survival parameters. The high temperature (21 °C) was the only factor that affected parental parameters (gonadosomatic index "GSI", and vitellogenin "VTG" particularly). On females, 21 °C had a stimulating effect on gonadal development evaluated by an early increase, followed by a sharp decrease of GSI, probably indicating gonadal atresia. Promoting effect of temperature was corroborated by an early production of VTG. In vitro fertilization assays showed interesting results, particularly cadmium effects. As it was supposed, high temperature had a negative impact on offspring parameters (significant decrease in survival and an increase of unhatched embryos). Parental exposure to the very low concentration of cadmium had also negative consequences on mortality rate (significant increase) and hatching rate (significant decrease). Our results indicate that in a global warming context, high temperature and its combination with contaminant may impact reproductive capacity of G. aculeatus, by decreasing parental investment (low eggs and/or sperm quality).

Physiological impacts of pollution exposure in seabird's progeny nesting in a Mediterranean contaminated area

Aquatic wildlife is exposed through trophic transfer of hazardous substances to several threats inducing physiological impairments. We aimed at assessing the impact of contamination in one of the hot spots of pollution along Mediterranean coasts, the gulf of Gabes in Tunisia, on Common tern Sterna hirundo, a piscivorous top predator bird. Firstly, we compared the reproductive effort of breeding adults through clutch size distribution in three sites with different levels of pollution. Then, a battery of genotoxicity and oxidative stress biomarkers was carried out to assess physiological impairments in chicks. While defense mechanisms showed a depletion, lipid peroxidation and genotoxicity increased significantly according to pollution level. The multi-biomarker approach used here, discriminated chicks according to contamination degree of their nesting sites. Increases in genotoxicity and oxidative stress were correlated to a decrease in chick body mass known to lead to long-term impacts on juvenile survival and recruitment in birds.

Assessment of sperm DNA integrity within the Palaemon longirostris (H. ) population of the Seine estuary

The interpretation of biomarkers in natura should be based on a referential of expected values in uncontaminated conditions. Nevertheless, to build a reference data set of biomarker responses in estuarine areas, which receive chronic pollution loads due to their transition position between continent and sea, is impossible. In this context, the aim of the present work was to propose the use of laboratory recovery period to define a baseline for the measurement of sperm DNA damage by Comet assay in the estuarine prawn Palaemon longirostris. For that, sperm DNA integrity was observed after both a passive (i.e. 20 days in a clean environment) and an active (i.e. forced renewal of spermatophores) recovery of wild P. longirostris specimens from the Seine estuary, in laboratory conditions. Then, the levels of sperm DNA damage recorded within the P. longirostris population of the Seine estuary, during six campaigns of sampling from April 2015 to October 2017, have been interpreted according to the defined threshold values. The results showed a persistence in the level of DNA damage after 20-day in clean environment with the passive recovery. This strategy was inconclusive to reach a baseline level but it revealed the lack of DNA repair mechanisms. For the active recovery, a decrease of 54% of the level of DNA damage has been observed after the first renewal of spermatophores and this level stabilized after the second renewal. On the basis of this second strategy, we defined a mean basal value of sperm DNA damage of 54.9 A.U. and a maximum threshold of 69.7 A.U. (i.e. 95 %CI). The analysis of the results using the reference value highlighted significant abnormal sperm DNA damage within the native population of P. longirostris from the Seine estuary on all stations during the six-sampling campaigns.

Signification of DNA integrity in sperm of Palaemon serratus (Pennant 1777): Kinetic responses and reproduction impairment

The study of the effects of contamination on sperm quality not only provides an early, specific and integrative response to the fraction of bioavailable pollutants, but also has been shown to predict the potential of this fraction to modify an organism's capacity to reproduce. In addition, fertility damage in invertebrates has been addressed as a major problem that may pose a threat to the maintenance of populations. In this context, the present study proposes a methodology based on the measurement of sperm DNA integrity to evaluate the impact of paternal damaged DNA on the reproductive success of Palaemon serratus. A preliminary methodological optimization step was carried out to assess the kinetics of response of spermatozoa as well as the sensitivity of the spermatozoa according to their location in the genital tract. Spermatozoa appeared to be sensitive to a short in vivo exposure to the direct acting agent methyl methanesulfonate (i.e. MMS; 2 days), with a persistence of damage even after a 30 days' recovery in a clean environment, suggesting a probable lack of DNA repair machinery. Moreover, our results revealed no difference in the level of DNA damage in mature spermatozoa whatever the exposure in spermatophore located in the terminal ampulla or in the proximal and distal part of the vas deferens. Finally, a significant decrease in the percentage of naturally bred prawns has been observed at the highest concentration of MMS (i.e. 100 μM). Nevertheless, no reproduction impairment (i.e. fertilization rate and early embryo development) following a paternal exposure has been shown in spite of very high levels of sperm DNA damage. In regard to the literature, this result raises questions concerning the kinetics of expression of genotoxic damage on progeny in the Palaemon model and future work will be led in this way.

Exposure of male tilapia (Oreochromis niloticus) to copper by intraperitoneal injection: DNA damage and larval impairment

The present work aimed to assess the genotoxic effects of intraperitoneally injected copper in males of O. niloticus, and to investigate its association with eventual changes in the quality of the gametes and in the generation of offspring abnormalities. Thus, to evaluate DNA damage, the alkaline comet assay was performed in sperm and blood; sperm parameters were analyzed to determine the quality of the gametes, and the incidence of morphological abnormalities of larvae, originated from eggs fertilized by males exposed to copper, was used as a measure of reproductive impairment. Male fish were exposed to three doses (1 mg/kg, 2 mg/kg, 4 mg/kg) of copper sulfate via intraperitoneal injection and observed after 96 h of exposure. We found that the quality of gametes was not affected by copper, as indicated by the lack of differences in sperm parameters between the exposed and the control groups. Nonetheless, copper induced an increase in sperm DNA damage at all tested doses. Taking into consideration the total number of abnormalities, larvae presented a higher proportion of morphological abnormalities at all the tested doses. Considering the morphological abnormalities separately, the 2 mg/kg and 4 mg/kg groups presented significantly higher frequencies of arrested development and spinal abnormalities than the control group. This work suggests that intraperitoneally injected copper is an inductor of DNA breakage in germ cells of O. niloticus males. Copper induces the formation of larval morphological abnormalities, causing reproductive impairment to this species. The fact that copper did not induce alterations on sperm parameters indicates that the parental genotoxic effects are inheritable to the offspring.

Effects of dietary microencapsulated Cymbopogon flexuosus essential oil on reproductive-related parameters in male Rhamdia quelen

In aquaculture, nutrition and supplemented diets have been shown to affect broodstock reproductive performance. In this study, we investigated the effects of dietary supplementation with Cymbopogon flexuosus essential oil (CFEO) microcapsules on reproductive-related parameters in silver catfish (Rhamdia quelen) male broodfish. Adult male broodstocks were separated into three groups according to the concentrations of supplemented CFEO (0.0 = control; 1.0 or 3.0 mL per kg of diet). After 20 days under experimental conditions, the animals were euthanized and the gonads were harvested for gonadosomatic index, sperm analysis, oxidative stress, and histopathology; testosterone levels were measured in the plasma; gene expression of prl, smtl, pomca, and pomcb was assessed in the pituitary gland by real-time PCR. The results showed no alterations on reproductive parameters in R. quelen males treated with Cymbopogon flexuosus essential oil compared to the control-diet animals. In conclusion, CFEO microcapsules supplied for 20 days in the concentrations of 1.00 or 3.00 mL per kilogram of diet did not affect the reproduction criteria evaluated in this study in male silver catfish.

Use of sperm DNA integrity as a marker for exposure to contamination in Palaemon serratus (Pennant 1777): Intrinsic variability, baseline level and in situ deployment

In a previous study, the Comet assay was optimized for Palaemon serratus prawns in order to propose a biomarker for sperm quality in this species. However, better knowledge of its basal level and its natural variability, related to intrinsic biotic and environmental abiotic factors, is required before any relevant use of this biomarker in the field. To fulfill this goal, the present study proceeded in three steps: (i) the temporal variability of DNA integrity was followed monthly in a reference population over a 2-year period, (ii) the correlation between the main intrinsic biotic (i.e. size, weight and molting stage) and abiotic factors (i.e. water temperature) were recorded in the field, and the basal DNA integrity was assessed in order to scrutinize any confounding influence of factors unrelated to toxic response, (iii) the baseline level was used to discriminate biomarker response among different stations displaying contrasting contamination levels. The results of the two-year monitoring in the reference population revealed no correlation between the levels of spermatozoa DNA damage and temperature, body size, weight or molting stage. Only a slight variability between monthly samplings was detected. On the basis of these field-collected data, we defined a reference distribution (i.e. 52.6 ± 5.6 A.U) with a threshold value (i.e. 61.7 A.U). Finally, this threshold value proved its relevance to discriminate among stations with contrasting pollution levels around the Seine Bay. Indeed, the results suggest significant DNA damage in populations nearest the Seine estuary, a major source of contaminants in the Bay, and a lower effect in populations further away from the estuary. The overall conclusion was that the Comet assay on P. serratus spermatozoa could be a useful tool for the monitoring of the toxicological print within sperm and main globally the contamination exposure of crustaceans in marine waters.

An integrative approach to assess ecological risks of surface water contamination for fish populations

Contamination of aquatic ecosystems is considered as one of the main threats to global freshwater biodiversity. Within the European Water Framework Directive (EU-WFD) a particular attention is dedicated to assess ecological risks of surface water contamination and mitigation of chemical pressures on aquatic ecosystems. In this work, we evaluated ecological risks of surface water contamination for fish populations in four EU-WFD rivers through an integrative approach investigating three Lines of Evidence (chemical contamination, biomarker responses as early warning signals of contamination impacting individuals and ecological analyses as an indicator of fish community disturbances). This work illustrates through 4 case studies the complementary role of biomarkers, chemical and ecological analyses which, used in combination, provide fundamental information to understand impacts of chemical pressures that can affect fish population dynamics. We discuss the limitations of this approach and future improvements needed within the EU-WFD to assess ecological risk of river contamination for fish populations.

Acclimation capacity of the three-spined stickleback (Gasterosteus aculeatus, L.) to a sudden biological stress following a polymetallic exposure

To get closer to the environmental reality, ecotoxicological studies should no longer consider the evaluation of a single pollutant, but rather combination of stress and their interaction. The aim of this study was to determine if responses of a fish to a sudden biological stress could be modified by a prior exposure to a chemical stress (a polymetallic contamination). For this purpose, in situ experiment was conducted in three ponds in the Haute-Vienne department (France). One pond was chosen for its high uranium concentration due to uranium mine tailings, and the two other ponds, which were not submitted to these tailings. Three-spined sticklebacks (Gasterosteus aculeatus) were caged in these ponds for 14 days. After this period, fish were submitted to a biological stress, exerted by lipopolysaccharides injection after anesthesia, and were sacrificed 4 days after these injections for multi-biomarkers analyses (leucocyte viability, phagocytic capacity and reactive oxygen species production, antioxidant peptide and enzymes, lipid peroxidation and DNA damage). The pond which received uranium mine tailings had higher metallic concentrations. Without biological stress, sticklebacks caged in this pond presented an oxidative stress, with increasing of reactive oxygen species levels, modification of some parts of the antioxidant system, and lipid peroxidation. Caging in the two most metal-contaminated ponds resulted in an increase of susceptibility of sticklebacks to the biological stress, preventing their phagocytic responses to lipopolysaccharides and modifying their glutathione contents and glutathione-S-transferase activity.

Effects of exposure to cadmium in sperm cells of zebrafish, Danio rerio

Cadmium is a natural element found in the earth’s crust; it is usually associated with other metals, but due to the impacts caused by human activity, its concentration has increased in the aquatic environment. This metal may damage aquatic animal reproduction, decreasing the rate of fertilization of organisms such as fish. Thus, this study aimed to evaluate the in vitro toxicity of different concentrations of cadmium (0 (control), 0.5, 5, and 10 μg/L) using sperm cells of model organism zebrafish, Danio rerio. Structural parameters, including integrity and fluidity of the plasma membrane, concentration of oxygen species, mitochondrial function and DNA fragmentation were measured by flow cytometry. The following sperm movement parameters were also measured using the computer assisted sperm analysis (CASA) system: motility, time of motility, curvilinear velocity, average path velocity and straight line velocity in μm/s. Significant effects were observed on path speed, straight speed, curvilinear velocity, motility time, progressive and total motility, and plasma and DNA integrity. The results showed that cadmium can negatively affect some reproductive parameters in D. rerio, which may reduce the fertility rate of these animals.

In situ effects of metal contamination from former uranium mining sites on the health of the three-spined stickleback (Gasterosteus aculeatus, L.)

Human activities have led to increased levels of various pollutants including metals in aquatic ecosystems. Increase of metallic concentrations in aquatic environments represents a potential risk to exposed organisms, including fish. The aim of this study was to characterize the environmental risk to fish health linked to a polymetallic contamination from former uranium mines in France. This contamination is characterized by metals naturally present in the areas (manganese and iron), uranium, and metals (aluminum and barium) added to precipitate uranium and its decay products. Effects from mine releases in two contaminated ponds (Pontabrier for Haute-Vienne Department and Saint-Pierre for Cantal Department) were compared to those assessed at four other ponds outside the influence of mine tailings (two reference ponds/department). In this way, 360 adult three-spined sticklebacks (Gasterosteus aculeatus) were caged for 28 days in these six ponds before biomarker analyses (immune system, antioxidant system, biometry, histology, DNA integrity, etc.). Ponds receiving uranium mine tailings presented higher concentrations of uranium, manganese and aluminum, especially for the Haute-Vienne Department. This uranium contamination could explain the higher bioaccumulation of this metal in fish caged in Pontabrier and Saint-Pierre Ponds. In the same way, many fish biomarkers (antioxidant and immune systems, acetylcholinesterase activity and biometric parameters) were impacted by this environmental exposure to mine tailings. This study shows the interest of caging and the use of a multi-biomarker approach in the study of a complex metallic contamination.

Ecological relevance of biomarkers in monitoring studies of macro-invertebrates and fish in Mediterranean rivers

Mediterranean rivers are probably one of the most singular and endangered ecosystems worldwide due to the presence of many endemic species and a long history of anthropogenic impacts. Besides a conservation value per se, biodiversity is related to the services that ecosystems provide to society and the ability of these to cope with stressors, including climate change. Using macro-invertebrates and fish as sentinel organisms, this overview presents a synthesis of the state of the art in the application of biomarkers (stress and enzymatic responses, endocrine disruptors, trophic tracers, energy and bile metabolites, genotoxic indicators, histopathological and behavioural alterations, and genetic and cutting edge omic markers) to determine the causes and effects of anthropogenic stressors on the biodiversity of European Mediterranean rivers. We also discuss how a careful selection of sentinel species according to their ecological traits and the food-web structure of Mediterranean rivers could increase the ecological relevance of biomarker responses. Further, we provide suggestions to better harmonise ecological realism with experimental design in biomarker studies, including statistical analyses, which may also deliver a more comprehensible message to managers and policy makers. By keeping on the safe side the health status of populations of multiple-species in a community, we advocate to increase the resilience of fluvial ecosystems to face present and forecasted stressors. In conclusion, this review provides evidence that multi-biomarker approaches detect early signs of impairment in populations, and supports their incorporation in the standardised procedures of the Water Frame Work Directive to better appraise the status of European water bodies.

Field evidence of reproduction impairment through sperm DNA damage in the fish nase (Chondrostoma nasus) in anthropized hydrosystems

This work aims to explore in the field the relationship between the integrity of sperm DNA and the quality of offspring as a possible cause of the decline of a feral fish population through reproduction impairment. Mature nase (Chondrostoma nasus) were caught during the breeding season in three locations (A-C) of the Rhône River basin and gametes collected by stripping. Sampling locations were chosen according to the following gradient of contamination due to human activities on the watershed: A≤B<C. Samples of a pool of collected oocytes were fertilized with the sperm of individual males and then incubated individually back in the lab to study embryo-larval development as well as using sperm samples to assess DNA integrity. Genetic analysis clearly showed the absence of a difference in genetic structure between the three studied C. nasus populations from the Rhône basin. Sperm DNA integrity was significantly lower in males from station C compared to other ones while sperm biochemical characteristics and fertilization rate remained almost unchanged whatever the station. Mortality and abnormality rates measured at both hatching and at the end of yolk sac resorption stages followed the same trend as the sperm DNA damage, demonstrating an impact of river water quality on nase fitness through a loss of sperm DNA integrity. Since the level of both abnormalities and mortality measured in offspring of fish caught in the most contaminated area reached high values up to 15% and 80%, respectively, the hypothesis that the observed nase decline in Rhône River stemming through selection forces can be put forward.

The Comet Assay and its applications in the field of ecotoxicology: a mature tool that continues to expand its perspectives

Since Singh and colleagues, in 1988, launched to the scientific community the alkaline Single Cell Gel Electrophoresis (SCGE) protocol, or Comet Assay, its uses and applications has been increasing. The thematic areas of its current employment in the evaluation of genetic toxicity are vast, either in vitro or in vivo, both in the laboratory and in the environment, terrestrial or aquatic. It has been applied to a wide range of experimental models: bacteria, fungi, cells culture, arthropods, fishes, amphibians, reptiles, mammals, and humans. This document is intended to be a comprehensive review of what has been published to date on the field of ecotoxicology, aiming at the following main aspects: (i) to show the most relevant experimental models used as bioindicators both in the laboratory and in the field. Fishes are clearly the most adopted group, reflecting their popularity as bioindicator models, as well as a primary concern over the aquatic environment health. Amphibians are among the most sensitive organisms to environmental changes, mainly due to an early aquatic-dependent development stage and a highly permeable skin. Moreover, in the terrestrial approach, earthworms, plants or mammalians are excellent organisms to be used as experimental models for genotoxic evaluation of pollutants, complex mix of pollutants and chemicals, in both laboratory and natural environment. (ii) To review the development and modifications of the protocols used and the cell types (or tissues) used. The most recent developments concern the adoption of the enzyme linked assay (digestion with lesion-specific repair endonucleases) and prediction of the ability to repair of oxidative DNA damage, which is becoming a widespread approach, albeit challenging. For practical/technical reasons, blood is the most common choice but tissues/cells like gills, sperm cells, early larval stages, coelomocytes, liver or kidney have been also used. (iii) To highlight correlations with other biomarkers. (iv) To build a constructive criticism and summarize the needs for protocol improvements for future test applications within the field of ecotoxicology. The Comet Assay is still developing and its potential is yet underexploited in experimental models, mesocosmos or natural ecosystems.

Genotoxicological response of the common carp (Cyprinus carpio) exposed to spring water in Tlaxcala, México

This study evaluated the genotoxic impact of anthropic activities in Huactzinco Spring, using Cyprinus carpio as a biomonitor. In situ and in vivo experimental designs were compared by means of simultaneous 2-week exposures. The water from the spring generated mean micronuclei frequency values (108.6 ± 32 MN/1,000) and DNA fragmentation values (143.4 ± 35 au) which were statistically higher than those for the negative control (10.9 ± 6 MN/1,000 and 67.6 ± 23 au). The in situ and in vivo experiments supported one another. The comet assay proved to be the most sensitive test, with an EC50 value (11.4 % ± 3.4 %) being less than that determined for the micronuclei test (54.8 % ± 3.2 %). The results of this study confirm the usefulness of C. carpio as an environmental contamination biomonitor, and suggest that Huactzinco Spring water constitutes a latent risk to human health and the environment.

Kinetic response of a genotoxicity biomarker in the three-spined stickleback and implication for environmental monitoring

The ultimate sink for the majority of anthropogenic compounds are the aquatic ecosystems, either through direct discharges or indirectly through hydrologic or atmospheric processes, possibly leading to long-term adverse effects in aquatic living resources. In order to assess exposure, fate and effects of chemical contaminants, aquatic ecotoxicologists have developed a large array of early-warning biomarkers proving that toxicants have entered organisms, have been distributed between organs and have triggered toxic effects regarding critical targets. However, optimal use of biomarkers in environmental studies previously requires in-depth knowledge of the kinetics of response of biomarkers. This work aimed to define as a first step of a validation process the kinetic response of a genotoxicity biomarker recently developed in the three-spined stickleback (Gasterosteus aculeatus). DNA damage was assessed in stickleback erythrocytes after in vivo exposure for 12 days to methylmethanesulfonate (MMS), an alkylating compound, followed by a 20 day-recovery period. Results show a dose-response relationship, time to maximal induction being reached after 6 days at the highest MMS concentration. No acclimation process was noticed during exposure whatever the MMS concentration, and genotoxicity decreased during the recovery phase only in fish exposed to the highest MMS concentration, suggesting more an effect of erythrocyte turn-over than of DNA repair system on the observed DNA damage level. Further field experiments are needed before including this genotoxicity biomarker in a battery of biochemical markers to monitor adverse effects of pollutants on fish health.

A multi-biomarker assessment of single and combined effects of norfloxacin and sulfamethoxazole on male goldfish (Carassius auratus)

In the present study, the sublethal effects of norfloxacin alone and in combination with sulfamethoxazole in goldfish (Carassius auratus) were investigated, the biomarkers including acetylcholinesterase (AChE) in brain, 7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST), and superoxides dismutase (SOD) activities in liver, vitellogenin (Vtg) in serum and DNA damage in gonad were determined after 1, 2, 4 and 7 days of exposure. Brain AChE activity was significantly inhibited by norfloxacin (≥0.4 mg/L) after 4 and 7 days and the mixtures with sulfamethoxazole (≥0.24 mg/L) after 4 days of exposure, and significant concentration-response relationships were obtained. Liver EROD, GST and SOD activities were significantly increased by the individual and mixed pharmaceuticals in most cases and exhibited analogously bell-shaped concentration-response curves. Serum Vtg was increased by the highest concentration of norfloxacin and two higher concentrations of the mixtures. Higher concentrations of the test antibiotics induced significant DNA damage in a concentration- and time-dependent manner. The results indicated that selected antibiotics possesses cytotoxic and genotoxic potential against the non-target organism C. auratus.

Study of genetic damage in the Japanese oyster induced by an environmentally-relevant exposure to diuron: evidence of vertical transmission of DNA damage

Pesticides represent a major proportion of the chemical pollutants detected in French coastal waters and hence a significant environmental risk with regards to marine organisms. Commercially-raised bivalves are particularly exposed to pollutants, among them pesticides, as shellfish farming zones are subject to considerable pressure from agricultural activities on the mainland. The aims of this study were to determine (1) the genotoxic effects of diuron exposure on oyster genitors and (2) the possible transmission of damaged DNA to offspring and its repercussions on oyster fitness. To investigate these points, oysters were exposed to concentrations of diuron close to those detected in the Marennes-Oleron Basin (two 7-day exposure pulses at 0.4 and 0.6 μg L(-1)) during the gametogenesis period. Genomic abnormalities were characterized using two complementary approaches. The Comet assay was applied for the measurement of early and reversible primary DNA damage, whereas flow cytometry was used to assess the clastogenic and aneugenic effect of diuron exposure. Polar Organic Chemical Integrative Samplers (POCIS) were used in exposed and assay tanks to confirm the waterborne concentration of diuron reached during the experiment. The results obtained by the Comet assay clearly showed a higher level of DNA strand breaks in both the hemocytes and spermatozoa of diuron-exposed genitors. The transmission of damaged genetic material to gamete cells could be responsible for the genetic damage measured in offspring. Indeed, flow cytometry analyses showed the presence of DNA breakage and a significant decrease in DNA content in spat from diuron-exposed genitors. The transmission of DNA damage to the offspring could be involved in the negative effects observed on offspring development (decrease in hatching rate, higher level of larval abnormalities, delay in metamorphosis) and growth. In this study, the vertical transmission of DNA damage was so highlighted by subjecting oyster genitors to short exposures to diuron at medium environmental concentrations. The analysis of POCIS showed that oysters were exposed to integrated concentrations as low as 0.2 and 0.3 μg L(-1), emphasizing the relevance of the results obtained and the risk associated to chemical contamination for oyster recruitment and fitness.

Oxidative damages and ultrastructural changes in the sperm of freshwater crab Sinopotamon henanense exposed to cadmium

The toxicity of several waterborne heavy metals to aquatic organisms is associated with oxidative damages due to the formation of reactive oxygen species (ROS). In the present work, the reproductive toxicity of the heavy metal cadmium was tested with the sperm of freshwater crab. The crabs were exposed to sublethal concentrations of 0, 7.25, 14.5, 29, 58 and 116 mg/L of Cd²⁺ for 3, 5 and 7 d. Cd²⁺ accumulation, ROS formation, and the total antioxidant capacity (TAC) in Sinopotamon henanense sperm were measured. Biomarkers of oxidative damage to lipid (Malondialdehyde, MDA), proteins (protein carbonyl derivates, PCO) and DNA (DNA-protein crosslinks, DPC) were investigated to address Cd²⁺ effects on crucial macromolecules of the S. henanense sperm. Transmission electron microscopy (TEM) was applied to assess ultrastructural changes induced by 29 and 116 mg/L Cd²⁺ exposure for 7 d. The results showed that sperm Cd²⁺ levels were significantly increased at 3, 5 and 7 d starting from the 14.5 mg L⁻¹ Cd²⁺-treated groups. Meanwhile, ROS levels were significantly increased over the experimental period. In terms of TAC, statistically significant changes were observed only at day 7 with the Cd²⁺ concentrations of 14.5, 29, 58 and 116 mg/L. This resulted in an increase of MDA content (5 d and 7 d), PCO content (Cd²⁺: 58 and 116 mg/L, 7 d), and DPC levels (Cd²⁺: 116 mg/L, 3 d and 7 d), by 26.32%, 37.47%, 22.04%, respectively, in the 116 mg/L Cd²⁺ group at day seven. For ultrastructural observations, the sperm membrane became wrinkled and partly dissolved, the nuclear envelope turned wrinkled and the chromatin condensed, the acrosome was incomplete with a damaged acrosomal membrane in crabs treated with 29 mg/L Cd²⁺ for 7 d. After treatment with 116 mg/L Cd²⁺ for 7 d, the sperm membrane was almost dissolved, the chromatin in the nucleus was more heavily condensed, chromatin irregularities and serious acrosome damage were observed.

Parental exposure to methyl methane sulfonate of three-spined stickleback: contribution of DNA damage in male and female germ cells to further development impairment in progeny

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.