Lizards as model organisms to evaluate environmental contamination and biomonitoring

Blood levels of metallic trace elements are influenced by sex, age and habitat in the European pond turtle (Emys orbicularis)

Metallic trace elements (MTEs) constitute a major source of chemical pollution and represent a threat to aquatic ecosystems and organisms. Important variation in contamination may exist at a local scale in relation to the environment (hydrosystem, trophic ressources) and individual traits (age, sex). Heretofore, the factors influencing MTEs exposure of freshwater reptiles in temperate regions are not fully understood. Freshwater turtles have a relatively high trophic position and a long lifespan, thus being potentially highly exposed due to bioaccumulation and bioamplification processes. We investigated MTE blood concentrations from two populations of the European pond turtle (Emys orbicularis) in the Camargue wetland (France). These populations, monitored since 1997, differ in their habitat and exposure (irrigation versus drainage canal). In this study, we detected 7 MTEs (Cu, Fe, Hg, Mn, Pb, Se, and Zn) which levels depended on site and individual characteristics. Hg was positively related to body size and age, indicating an increase of exposure in older individuals. We found differences between males and females with the interaction with body size for Pb and Se and with age for Pb. Nitrogen and carbon stable isotopes varied only marginally between individuals and were poorly associated with MTEs concentrations, showing that trophic position might not explain MTEs contamination for these populations. At the individual level, Hg, Pb, and Se blood values were repeatable over years. Further studies should concentrate on potential ecophysiological effects to such exposure, especially since we recently evidenced that these populations of E. orbicularis are highly exposed to organic contaminants, which can lead to synergistic effects.

Evaluation of herbicide toxicity to Lemna minor L. and Azolla caroliniana Willd

Long-residual herbicides can negatively impact aquatic ecosystems through surface runoff and leaching. This study evaluated the acute toxicity of indaziflam, sulfentrazone, clomazone, and tebuthiuron on Lemna minor and Azolla caroliniana. Experiments were conducted in the laboratory using a completely randomized design (CRD) with six concentrations of each herbicide across four replicates. The study assessed the concentration causing acute effects in 50% of the organisms (EC50), the effects on fresh weight (g), and the risk quotient (RQ). For L. minor, EC50 values were 0.41, 0.73, 0.12, and 0.21 mg L⁻¹ for clomazone, sulfentrazone, indaziflam, and tebuthiuron, respectively; and for A. caroliniana, the values were 3.26, 0.51, 0.11, and 0.71 mg L⁻¹, respectively. All tested herbicides were classified as highly toxic to macrophyte species, except for clomazone, which was categorized as 'moderately toxic' for A. caroliniana. Moreover, these herbicides significantly reduced fresh weight even at the lowest concentrations.

Microplastic accumulation in a lizard species: Observations from the terrestrial environments

Microplastics are a global environmental problem, polluting both aquatic and terrestrial environments. Terrestrial lizards are suitable model organisms to study human-induced pollution in these areas, as they can live in urbanized areas where microplastics are most abundant. Therefore, we analyzed the prevalence of microplastics (MPs) in a common Lacertid lizard, the snake-eyed lizard, Ophisops elegans. We detected MPs in the gastrointestinal tract (GIT) of 33 of 152 specimens from 18 populations. The detected MPs had six distinct polymer compositions, namely Polyethylene terephthalate, Polyacrylonitrile, Polypropylene, Polyethylene, Poly methyl methacrylate and Polyamide. The majority of these MPs were fiber-type and the dominant color was navy blue. The lengths of MPs varied from 37 to 563 μm, with an average length of 175 μm. MPs were detected in the GITs of 43% of juveniles (n = 7), 30% of males (n = 105), and 18% of females (n = 40), with a mean of 0.27 per specimen. Furthermore, we found that microplastic densities varied with habitat distance from human settlements, supporting the theory that high levels of microplastic contamination are associated with extensive anthropogenic activity.

Wildlife ecotoxicology of plant protection products: knowns and unknowns about the impacts of currently used pesticides on terrestrial vertebrate biodiversity

Agricultural practices are a major cause of the current loss of biodiversity. Among postwar agricultural intensification practices, the use of plant protection products (PPPs) might be one of the prominent drivers of the loss of wildlife diversity in agroecosystems. A collective scientific assessment was performed upon the request of the French Ministries responsible for the Environment, for Agriculture and for Research to review the impacts of PPPs on biodiversity and ecosystem services based on the scientific literature. While the effects of legacy banned PPPs on ecosystems and the underlying mechanisms are well documented, the impacts of current use pesticides (CUPs) on biodiversity have rarely been reviewed. Here, we provide an overview of the available knowledge related to the impacts of PPPs, including biopesticides, on terrestrial vertebrates (i.e. herptiles, birds including raptors, bats and small and large mammals). We focused essentially on CUPs and on endpoints at the subindividual, individual, population and community levels, which ultimately linked with effects on biodiversity. We address both direct toxic effects and indirect effects related to ecological processes and review the existing knowledge about wildlife exposure to PPPs. The effects of PPPs on ecological functions and ecosystem services are discussed, as are the aggravating or mitigating factors. Finally, a synthesis of knowns and unknowns is provided, and we identify priorities to fill gaps in knowledge and perspectives for research and wildlife conservation.

Pesticides compromise health: a comparison between lizards collected within and outside an agricultural area

Reptiles are the least studied vertebrates regarding the impact of pesticides on their health, despite being good models for ecotoxicological studies given their abundance and easy handling. Salvator merianae is widely distributed in South America and often found in agricultural cultivation areas. Here, we compared the morphological, biochemical, and physiological parameters of S. merianae from an exposed area (EA) to pesticides and a reference area (RA) or control. These parameters were measured in plasma (albumin, alanine transaminase, alkaline phosphatase, gamma-glutamyl transpeptidase, glucose, total proteins, uric acid, triglycerides, VLDL, and corticosterone) and in erythrocytes (TBARS, glutathione S-transferase, superoxide dismutase, and catalase activity). Blood samples were collected from 28 lizards (EA: three juveniles, three adult females, and three adult males; RA: nine juveniles, four females, and five males) in southern Brazil during the reproductive period. We observed a decrease in body mass, the ratio between body mass and total length and snout-vent length in juvenile lizards collected at EA. The levels of TBARS, glutathione S-transferase, triglycerides, VLDL, and uric acid were altered for juveniles in EA. When comparing the two areas, females differed in superoxide dismutase activity and total proteins, while males differed in superoxide dismutase, catalase, and glutathione S-transferase activity. This set of results shows that S. merianae, especially juveniles, suffers a negative impact when inserted in an agricultural area. The analyzed biomarkers proved suitable for monitoring these lizards and the quality of this environment.

Immuno-endocrine alterations and oxidative stress induced by commercial formulations of pesticides in the tegu lizard (Salvator merianae)

Recent research has shown the risk of environmental contamination by pesticides in Argentina. Salvator merianae is considered as "sentinel species" for monitoring their effects. We intended to investigate growth, immunological and endocrine functions, and oxidative stress in S. merianae exposed to two commercial brands of the herbicide glyphosate: Roundup and Panzer Gold, as well as, to two insecticides: chlorpyrifos, and cypermethrin. Our results showed a higher increase in growth in animals exposed to Roundup and chlorpyrifos and a lower increase in those exposed to Panzer Gold. Higher total leukocyte and lymphocyte count values were observed in lizards exposed to Panzer Gold. The heterophils/lymphocytes ratio decreased in all treated animals. Regarding lobularity index, natural antibodies titers, and complement system activity values, lizards exposed to cypermethrin had higher values. Low corticosterone levels were observed in animals exposed to Roundup. Our results reveal different toxic effects of pesticides contributing to the knowledge of the pesticides' potential deleterious impact in the habitat of S. merianae.

Metal contents in house geckos (Squamata: Gekkonidae) from industrial and urban areas of southern Tamaulipas, Mexico and western Andalucía, Spain, may reflect airborne metal pollution

House geckos share living quarters with humans in the tropical and subtropical regions inhabited by these reptiles. Gecko behavior, biological traits, continuous exposure to suspended particulate matter 0 µm in diameter (PM₁₀) and dust, as well as status as exotic species, motivated the choice of these species to examine environmental exposure to ambient air pollutants, in particular metals, and subsequent accumulation in these organisms. One part of the study was conducted in Tamaulipas (Mexico) where Hemydactylus frenatus is abundant in urban and industrial environments, the other part was conducted in Andalucia (Spain) where Tarentola mauritanica is found in similar environments. Adult geckos were collected on buildings in locations affected by various air pollution sources. For both species, higher metal contents were observed in whole-body (including digestive tracts) analysis and were markedly different between collection sites. Contents in tails, digestive tracts, and carcasses without digestive tracts were not correlated. Based on contamination factor values, bioaccumulation in H. frenatus tissues occurred for 12 of the 15 metals analyzed. Data suggest that H. frenatus might serve as a biomonitor for Cu, Ni, Pb, Cr, Li, and V, whereas T. mauritanica might be a biomonitor for Cu, Ni, Pb, and Cr. To our knowledge, metal contents for H. frenatus are reported here for the first time. House gecko data could be integrated into a highly representative monitoring system and health risk assessments related to air quality in residential areas.

Molecular and Histological Effects of Glyphosate on Testicular Tissue of the Lizard Podarcis siculus

The expansion of agriculture produces a steady increase in habitat fragmentation and degradation due to the increased use of pesticides and herbicides. Habitat loss and alteration associated with crop production play an important role in reptile decline, among which lizards are particularly endangered. In this study, we evaluated testicular structure, steroidogenesis, and estrogen receptor expression/localization after three weeks of oral exposure to glyphosate at 0.05 and 0.5 μg/kg body weight every other day in the field lizard Podarcis siculus. Our results show that glyphosate affected testicular morphology, reduced spermatogenesis, altered gap junctions and changed the localization of estrogen receptors in germ cells, increasing their expression; the effects were mostly dose-dependent. The result also demonstrates that glyphosate, at least at these concentrations, did not influence steroidogenesis. Overall, the data indicate that this herbicide can disturb the morphophysiology of the male lizard's reproductive system, with obviously detrimental effects on their reproductive fitness. The effects of glyphosate must be considered biologically relevant and could endanger the reproductive capacity not only of lizards but also of other vertebrates, including humans; a more controlled and less intensive use of glyphosate in areas devoted to crop production would therefore be advisable.

Behavioral fever in Bosk's fringe-toed lizards (Acanthodactylus boskianus) living in an industrial area in south-eastern Tunisia

As an indicator of physiological state of lizards, thermoregulatory behavior has been proposed as an assessment tool of environmental contamination, particularly in desert ecosystems where lizards represent a major biological component. Although pesticide contamination has been shown to induce behavioral fever in lizards, the possible pyrogenic effect of heavy metals has received less attention. The objective of this study was to provide data on this issue by using Bosk's fringe-toed lizards (Acanthodactylus boskianus) living in a metal-contaminated industrial area in south-eastern Tunisia as a study model. Combining field observations of behavior with measures of thermoregulatory performance under laboratory conditions, we found that proximity to the industrial zone was associated to a different thermoregulatory behavior of lizards. There was a tendency of lizards living close to the contamination source to display behavioral fever, as they spent more time in the sun, preferred higher body temperatures, and warmed up faster, compared to lizards living far away. This heat-seeking behavior is likely a reaction to improve the functioning of physiological systems involved in the defense against toxic effects of heavy metals, possibly through the increase of metabolic rate, stimulation of enzymes involved in the detoxification process, and enhancement of immune defense systems. Our findings stress the need for further detailed studies into the physiological mechanisms linking metal contamination to behavioral fever. They also underline the usefulness of thermoregulatory behavior as a reliable, non-destructive, and inexpensive, individual-level biomarker in lizard ecotoxicology and biomonitoring of contaminated desert environments.

Combining ecological, eco-cultural, and environmental justice parameters to create Eco-EJ indicators to monitor cultural and environmental justices for diverse communities around contaminated sites

Assessing environmental quality often requires selection of indicators that can be employed over large spatial scales and over long-time periods to assess the health and well-being of species, natural communities, and ecosystems, and to detect changes warranting intervention. Typically, the ecologic environment and the human environment are evaluated separately and selection of indicators and monitoring approaches are not integrated even though ecological indicators may also provide information on risk to human consumers from contaminants (e.g., eco-cultural indicators) or because of disease levels. This paper is a call for ecologists and managers to consider diverse cultural and environmental injustice disparities and health issues when selecting indicators for environmental assessment and monitoring. There is an opportunity for managers and community members to work together to preserve ecological and cultural resources and heritages. We propose a paradigm that selects indicators and monitoring approaches that lend themselves to the integration of human-diversity and uniqueness in the same manner that the selection of ecological indicators and monitoring approaches consider biological species diversity and uniqueness. The proposed paradigm builds on ecological risk assessment techniques, developing analogous endpoints for neighboring communities. For example, identification and protection of human communities, particularly culturally diverse and environmental justice communities, identification of contaminant corridors (e.g., through water or green corridors) into communities, and eco-monitoring of vulnerable communities are not routine at contaminated sites. Green corridors refers to a width of wild habitat (forest, grasslands) that connects other similar habitat paths (usually a corridor runs through an urban or suburban habitat). We coin the term Eco-EJ indicators for these endpoints, including examination of (1) unique cultural relationships to resources; (2) connectedness of on-site and off-site resources and habitats; (3) health of threatened, rare, and unique cultures and communities; and (4) linkages between ecological, eco-cultural, and public health for monitoring and assessment. We also propose that assessment and monitoring include these Eco-EJ indicators, especially for communities near facilities that have extensive chemical or radiological contamination.Developing these indicators to assess risk to culturally diverse and environmental justice communities would be an equivalent goal to reducing risk for significant ecological resources (e.g., endangered species, species of special concern). These Eco-EJ indicators are complementary to the usual human health-risk assessments, would include surveys of neighboring vulnerable communities, and require time and re-organization of current data and additional data collection at site boundaries and in adjacent communities, as well as rethinking the human component of indicators. This approach lends itself to addressing some diverse cultural and environmental justice issues with current indicator selection and biomonitoring, and helps identify specific hotspots of unique ecosystem risk and environmental justice community risk. We briefly discuss ecological and eco-cultural monitoring already on-going at three Department of Energy sites to illustrate how the addition of these indicators might work and add value to environmental management and to their relationships with surrounding communities. We recommend that managers of contaminated sites convene people from culturally diverse communities, environmental justice communities, local and federal government, Tribes, resource trustees, managers, and other stakeholders to develop appropriate site-specific indicators to address environmental inequities around contaminated facilities.

Snakes as bimonitors of environmental pollution: A review on organic contaminants

Monitoring data on organic pollutants published between the late 1960s and 2020 are reviewed to provide comprehensive and updated insights into their bioaccumulation characteristics, sources, and fate in snakes. Multiple organic pollutant classes including pesticides, polychlorinated biphenyls, chlorinated paraffins, dioxin-related compounds, alkanes, polycyclic aromatic hydrocarbons, flame retardants, plasticizers, etc., were detected in various aquatic and terrestrial snake species with concentrations and patterns varying between species and locations. In general, higher concentrations of organic pollutants were found in snakes collected from contaminated sites (e.g., densely populated, pesticide-treated, and waste processing areas), suggesting that snakes can serve as good biomonitors of environmental pollution caused by organic contaminants. Factors influencing concentrations and patterns of organic pollutants in snakes are discussed, providing an overview of current understanding about their accumulation, transformation, and elimination processes. Potential negative effects associated with organic pollutants in snakes and their predators are also considered. Based on such discussions, research gaps and future perspectives on the utilization of snake biomonitoring studies are addressed, heading towards an effective monitoring and assessment scheme for a variety of legacy and emerging organic pollutants in the environment.

Review of petroleum toxicity in marine reptiles

Worldwide petroleum exploration and transportation continue to impact the health of the marine environment through both catastrophic and chronic spillage. Of the impacted fauna, marine reptiles are often overlooked. While marine reptiles are sensitive to xenobiotics, there is a paucity of petroleum toxicity data for these specialized fauna in peer reviewed literature. Here we review the known impacts of petroleum spillage to marine reptiles, specifically to marine turtles and iguanas with an emphasis on physiology and fitness related toxicological effects. Secondly, we recommend standardized toxicity testing on surrogate species to elucidate the mechanisms by which petroleum related mortalities occur in the field following catastrophic spillage and to better link physiological and fitness related endpoints. Finally, we propose that marine reptiles could serve as sentinel species for marine ecosystem monitoring in the case of petroleum spillage. Comprehensive petroleum toxicity data on marine reptiles is needed in order to serve as a foundation for future research with newer, unconventional crude oils of unknown toxicity such as diluted bitumen.

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.