Application of the comet assay, micronucleus test and global DNA methylation analysis in Darevskia lizards as a sentinel organism for genotoxic monitoring of soil pollution

Congenital malformation in green turtle embryos and hatchlings

Successful embryonic development depends on the interaction between genetic factors and environmental variables. Congenital malformations in sea turtles can result from extreme conditions during the incubation period, reducing hatching success and potentially impeding population recovery. We aimed to characterize the congenital malformations found in green turtle nests, determine their prevalence and severity, and understand their drivers during the 2022 nesting season on Samandağ beach on northern Mediterranean nesting beaches. A total of 2986 examples of congenital malformations were observed in 362 out of 907 green turtle nests. The prevalence of congenital malformations per nest was 39%, and the severity (the number of malformed individuals per nest) was 3.8%. Nests with congenital malformations exhibited a lower mean distance from the sea, a shorter incubation duration (a proxy for incubation temperature), lower hatching success, a larger clutch size, and higher mortality at late embryonic and hatchling stages than nests without congenital malformations. There was no significant difference in total mortality between these two nest types. A total of 52 different congenital malformations were recorded, 2 of which were observed for the first time in sea turtles and 28 for the first time in green turtles. The results suggest that congenital malformations may be related to nest temperature and clutch size, while overall mortality may be independent of malformations. Pigmentation disorders and craniofacial malformations typically coexist in cases of multiple malformations. Long-term monitoring of congenital malformations is crucial, as it can provide clues about the health status of the nesting beach and nesting colony.

Micronucleus test in reptiles: Current and future perspectives

Micronucleus (MN) cell counting emerged in 1973-1975 as a valid alternative for characterizing chromosomal damage caused by different agents. It was first described in mammals, but its application was rapidly extended to other vertebrates, mainly fish. However, it was not until 28 years later that this test was implemented in studies on reptiles. Nowadays, reptiles are found to be excellent non-target species from environmental contamination exposure and MN test has become a fundamental tool for analyzing genotoxic effects induced by various xenobiotics. In this article we provide an updated review of the application of the MN test in reptile species, from an ecotoxicological perspective. Therefore, we present (I) a bibliometric analysis of the available research on genotoxic-induced MN formation in reptile species; (II) the use of reptiles as sentinel organisms in ecotoxicological studies; and (III) the strength and weakness of the application of the MN test in this group. With this review, we aim to provide a comprehensive view on the use of the MN test in ecotoxicology and to encourage further studies involving reptile species.

Ecogenotoxicity assessment with land snails: A mini-review

In the context of the increasing environmental and sanitary crisis, it is accepted that soil pollution can cause health alterations and disturb natural population dynamics. Consequently, the assessment of the genotoxic potential of compounds found in contaminated soils is important. Indeed, the alteration of genomic integrity may increase the risk of cancer development and may impair reproduction and long-term population dynamics. Among the methodologies to assess terrestrial genotoxic potential, there has been growing interest during the last decade in monitoring alterations of the genome in bioindicators of soil quality. As some land snail species are recognized bioindicators of soil quality, especially to assess the environmental and toxicological bioavailability of compounds, this review focuses on current knowledge regarding the genotoxicology of land snails. Classical biomarkers to assess genotoxic effects have been used (e.g., DNA breakage, micronuclei, random amplification polymorphic DNA) at various stages of the life cycle, including embryos. The studies were performed in vitro, in vivo, in situ and ex situ and covered a diverse set of contaminants (nanoparticles, metal(loid)s, pesticides, polycyclic aromatic hydrocarbons) and snail species (Cantareus aspersus, Eobania vermiculata, Theba pisana, Helix lucorum). Based on recent studies reviewed here, the use of land snails to map soil genotoxic potential is promising due to their ability to reveal pollution and subsequent environmental risks. Moreover, the position of snails in the trophic chain and the existing bridges between contaminant bioavailability to snails and bioaccessibility to humans reinforce the value of land snail-based ecotoxicological assessment.

Application of land snail Helix lucorum for evaluation of genotoxicity of soil pollution

Application of native species as sentinels allows environmental scientists to determine real genotoxic impact of environmental pollutants. The present study aims at investigating the DNA damage in the land snail Helix lucorum as a biomarker of soil pollution. For this reason, the genotoxic impact of contaminated soil on H. lucorum, collected from different polluted areas, was investigated using the comet assay in haemocytes and digestive gland cells. An increase in DNA damage was found in the snails sampled from polluted sites compared with the reference one. Strong correlations between DNA damage in haemocytes and digestive gland cells with the level of contamination indicate pollution-induced genotoxic effects in both tissues. At the same time, the digestive gland was more sensitive towards pollutants compared with haemolymph. A direct relationship between concentrations of Cu, As and Mo in soil and the number of damaged cells for hаemolymph and digestive gland tissue was found. However, the data obtained reflect the total genotoxicity of all pollutants in the studied areas. Significant correlations between the DNA damage measured by the comet assay and metal contents in soil indicate that it is a suitable biomarker in ecotoxicological studies. Our results indicate the effectiveness of H. lucorum in biomonitoring of environmental pollution.

Epigenetic Measurement of Key Vertebrate Population Biology Parameters

The age, sex, and sexual maturity of individual animals are key parameters in assessing wild populations and informing conservation management strategies. These parameters represent the reproductive potential of a population and can indicate recovery rates or vulnerabilities. Natural populations of wild animals are difficult to study; logistically, economically, and due to the impacts of invasive biomonitoring. Genetic and epigenetic analyses offer a low impact, low cost, and information-rich alternative. As epigenetic mechanisms are intrinsically linked with both biological aging and reproductive processes, DNA methylation can be used as a suitable biomarker for population biology study. This review assesses published research utilizing DNA methylation analysis in relation to three key population parameters: age, sex, and sexual maturity. We review studies on wild vertebrates that investigate epigenetic age relationships, with successful age estimation assays designed for mammals, birds, and fish. For both determination of sex and identification of sexual maturity, very little has been explored regarding DNA methylation-based assays. Related research, however, confirms the links between DNA methylation and these processes. Future development of age estimation assays for underrepresented and key conservation taxa is suggested, as is the experimental development and design of DNA methylation-based assays for both sex and sexual maturity identification, further expanding the genomics toolkit for population biology studies.

Intergenerational Patterns of DNA Methylation in Procambarus clarkii Following Exposure to Genotoxicants: A Conjugation in Past Simple or Past Continuous?

Epigenome is susceptible to modulation by environmental pressures—namely, through alterations in global DNA methylation, impacting the organism condition and, ultimately, reverberating on the phenotype of the subsequent generations. Hence, an intergenerational study was conducted, aiming to clarify the influence of genotoxicants on global DNA methylation of the crayfish Procambarus clarkii. Two subsequent generations were exposed to the herbicide penoxsulam (Px; 23 µg·L⁻¹) and to the genotoxicant model ethyl methanesulfonate (EMS; 5 mg·L⁻¹). Px did not induce changes in DNA methylation of adult crayfish (F₀). However, the hypomethylation occurring in unexposed F₁ juveniles demonstrated that the history of exposure per se can modulate epigenome. In F₁ descendants of the Px-exposed group, methylome (hypermethylated) was more affected in males than in females. EMS-induced hypomethylation in adult females (F₀), also showed gender specificity. In addition, hypomethylation was also observed in the unexposed F₁ crayfish, indicating an intergenerational epigenetic effect. The modulatory role of past exposure to penoxsulam or to EMS also showed a dependency on the crayfish developmental stage. Overall, this research revealed that indirect experiences (events occurring in a predecessor generation) can have an impact even greater than direct experiences (present events) on the epigenetic dynamics.

Cellular Responses Induced by Zinc in Zebra Mussel Haemocytes. Loss of DNA Integrity as a Cellular Mechanism to Evaluate the Suitability of Nanocellulose-Based Materials in Nanoremediation

Zinc environmental levels are increasing due to human activities, posing a threat to ecosystems and human health. Therefore, new tools able to remediate Zn contamination in freshwater are highly recommended. Specimens of Dreissena polymorpha (zebra mussel) were exposed for 48 h and 7 days to a wide range of ZnCl2 nominal concentrations (1-10-50-100 mg/L), including those environmentally relevant. Cellulose-based nanosponges (CNS) were also tested to assess their safety and suitability for Zn removal from freshwater. Zebra mussels were exposed to 50 mg/L ZnCl2 alone or incubated with 1.25 g/L of CNS (2 h) and then removed by filtration. The effect of Zn decontamination induced by CNS has been verified by the acute toxicity bioassay Microtox®. DNA primary damage was investigated by the Comet assay; micronuclei frequency and nuclear morphological alterations were assessed by Cytome assay in mussels' haemocytes. The results confirmed the genotoxic effect of ZnCl2 in zebra mussel haemocytes at 48 h and 7-day exposure time. Zinc concentrations were measured in CNS, suggesting that cellulose-based nanosponges were able to remove Zn(II) by reducing its levels in exposure waters and soft tissues of D. polymorpha in agreement with the observed restoration of genetic damage exerted by zinc exposure alone.

Toxicity of polystyrene nanoplastics and zinc oxide to mice

The toxicity of zinc oxide (ZnO NPs) and polystyrene nanoplastics (PS NaPs) has been tested in different animal models; however, knowledge about their impact on mice remains incipient. The aim of the current study is to evaluate the effects of these nanomaterials on Swiss mice after their individual exposure to a binary combination of them. The goal was to investigate whether short exposure (three days) to an environmentally relevant dose (14.6 ng/kg, i.p.) of these pollutants would have neurotoxic, biochemical and genotoxic effects on the modelss. Data in the current study have shown that the individual exposure of these animals has led to cognitive impairment based on the object recognition test, although the exposure experiment did not cause locomotor and anxiogenic or anxiolitic-like behavioral changes in them. This outcome was associated with increased nitric oxide levels, thiobarbituric acid reactive species, reduction in acetylcholinesterase activity and with the accumulation of nanomaterials in their brains. Results recorded for the assessed parameters did not differ between the control group and the groups exposed to the binary combination of pollutants. However, both the individual and the combined exposures caused erythrocyte DNA damages associated with hypercholesterolemic and hypertriglyceridemic conditions due to the presence of nanomaterials. Based on the results, the toxicological potential of ZnO NPs and PS NaPs in the models was confirmed and it encouraged further in-depth investigations about factors explaining the lack of additive or synergistic effect caused by the combined exposure to the assessed pollutants.

Cytogenetic analysis of nuclear abnormalities in the erythrocytes of gecko lizards (Phyllopezus periosus) collected in a semi-arid region of northeast Brazil: Possible effects of natural background radioactivity

High natural-background radioactivity levels occur in the semi-arid region of the State of Rio Grande do Norte, northeastern Brazil. We have studied the lizard Phyllopezus periosus, an endemic species of the Brazilian caatinga with saxicolous habitat, as a bioindicator of environmental quality. Specimens were collected in three areas, an environmental protection area and two areas recognized as having high natural background radiation, one of these being a mining area. Level of metals and gamma radiation emitters present in the water sources potentially used by the lizards were measured. The biological endpoints assessed were micronuclei and nuclear abnormalities in blood samples. Significant differences in background radioactivity levels were found among the assessed areas. Statistically significant differences in micronuclei and nuclear abnormality frequencies were seen, among the study areas and a relationship between radioactivity level and genetic damage was observed.

Lizards as model organisms to evaluate environmental contamination and biomonitoring

Environmental contamination is reaching ever higher levels and affecting several animal populations, including humans. In this context, studies are being developed to monitor and evaluate this environmental problem using bioindicators organisms, in addition to testing the toxicity of contaminants in the laboratory. In this perspective, reptiles are ideal animals for these types of studies, considering that they are ectothermic and have a slower metabolism directly influencing their recovery power, and therefore, they are more sensitive to xenobiotic effects. Among reptiles, lizards are animals that adapt to various environmental conditions, even being found in areas with arid characteristics. Therefore, a literature review was conducted in this study regarding the use of lizards as models for ecotoxicological studies, including biomonitoring, carried out in the last 10 years, with the aim of evaluating them as bioindicators in Brazilian semi-arid region. Studies were found involving ten lizard families, among which the most investigated was Lacertidae. The studies were classified into two categories: organic contaminants (pesticides, petroleum by-products, and explosives) and inorganic contaminants (metals such as zinc, lead and aluminum, and radionuclides). Contaminants directly contributed to DNA damage and to increasing the frequency of micronuclei in exposed animals, histopathological effects, and oxidative stress. The performed analysis highlights the usefulness of lizards as environmental biomonitors. However, the response profile is dependent on the exposure level and route, in addition to the environmental scenario analyzed. Therefore, future studies aimed at evaluating environmental contaminants are required under exposure conditions more related to the environmental reality to be studied.

Enrichment of imidacloprid and its metabolites in lizards and its toxic effects on gonads

Soil contaminants can cause direct harm to lizards due to their regular swallowing of soil particles. As the world's fastest growing insecticide with long half-life in soil, the endocrine disrupting effect of neonicotinoids on lizards deserves more attention. In this report, we assessed the endocrine disrupting effect of imidacloprid on Eremias argus during 28 days of continuous exposure. Among the imidacloprid and its metabolites, only the metabolite 6-chloropyridic acid had a significant accumulation in the gonads and was positively correlated with its blood concentration. Imidacloprid might cause endocrine disrupting effects on lizards in two ways. First, the desnitro metabolites of imidacloprid could accumulate in the brain, inhibited the secretion of gonadotropin-releasing hormone, and ultimately affected the feedback regulation of hypothalamic-pituitary-gonadal related hormones. Secondly, imidacloprid severely inhibited the gene expression of the corresponding enzymes in the gonadal anti-oxidative stress system, causing histological damage to the gonads and ultimately affecting gonadal function. Specifically, exposure to imidacloprid resulted in abnormal arrangement of spermatogenic epithelial epithelium, hyperplasia of epididymal wall, and oligospermia of male lizard. Meanwhile, gene expressions of cyp17, cyp19, and hsd17β were severely inhibited in the imidacloprid exposure group, consistent with decreased levels of testosterone and estradiol in plasma. Imidacloprid exposure could cause insufficient androgen secretion and less spermatogenesis in male lizards. The risk of imidacloprid exposure to female lizards was not as severe as that of male lizards, but it still inhibited the expression of cyp19 in the ovaries and led to a decrease in the synthesis of estradiol. This study firstly reported the endocrine disruption of imidacloprid to lizards, providing new data for limiting the use of neonicotinoids.

Alterations to DNA, apoptosis and oxidative damage induced by sucralose in blood cells of Cyprinus carpio

Sucralose (SUC) is an organochlorine that is used as a common sweetener in different dietary products around the world. Its extended use and production have led to this product is released into the environment in concentrations ranging from ng L^-1 to μg L^-1 in surface waters, groundwaters, wastewater treatment plants and ocean waters. A previous study carried out by our research team demonstrated that SUC is capable of inducing oxidative stress in Cyprinus carpio at environmentally-relevant concentrations. The aim of this study was to evaluate if SUC was capable of inducing alterations to DNA, apoptosis, and oxidative damage in the blood cells of C. carpio. Carps were exposed to two environmentally-relevant concentrations (0.05 and 155 μg L^-1) of SUC, and the following biomarkers were determined: comet assay, micronucleus test (MN), caspase-3 activity, TUNEL assay, hydroperoxide content, lipid peroxidation level, protein carbonyl content and superoxide dismutase and catalase activities. Results obtained showed that SUC is capable of inducing DNA damage. A maximum increase of 35% and 23% were observed for c1 and c2, respectively in the comet assay; increases of 586% and 507.7% for c1 and c2, respectively, were found at 72 h through the MN test. The activity of caspase-3 showed a greater response for c1 and c2 at 96 h, with 271% and 493.5%, respectively. TUNEL assay also showed the highest response at 96 h, with 51.8 for c1 and 72.9 for c2; c1 y c2 were able to induce oxidative stress with the highest expression at 72 h. A correlation between DNA damage biomarkers, apoptosis and plasma levels of SUC in both concentrations were observed. With the data obtained, we can conclude that SUC, at environmentally-relevant concentrations, was capable of generating DNA alterations, apoptosis and oxidative stress in blood cells in common carp.