Lizards as an unconventional model to evaluate the effects of contaminants on soil organisms.

Soil is the Earth's upper layer that sustains plant life, hosts an extraordinary biodiversity, and plays a key role in ecosystem functioning. But the excessive use of agrochemicals to increase agricultural productivity and the constant discharge of industrial and urban waste have resulted in the slow decline of soil quality. This situation has underscored the importance of preserving terrestrial ecosystems, and there is growing interest in developing effective and sustainable remediation strategies. Model organisms and reliable biomarkers are needed to assess the effectiveness of such interventions. Ecotoxicological studies most often use invertebrates, such as earthworms and snails, as biological models, but the results obtained cannot be easily extrapolated to more complex organisms such as terrestrial vertebrates, including humans. In this respect, terrestrial lizards have proven to be promising experimental models. They have a smaller range than birds and fewer ethical considerations than small mammals. In recent years, research on the Italian field lizard Podarcis siculus has provided insights into the bioaccumulation and toxicological effects of soil contaminants in terrestrial vertebrates. Histological analyses showed significant vacuolization of hepatocytes and atrophy of gonadal tissue in samples exposed to environmentally relevant concentrations of glyphosate and cadmium. Moreover, molecular analyses showed a dose-dependent induction of the stress response gene Hsp70 in the liver of cadmium-exposed animals, which strongly correlated with the extent of tissue damage. In individuals exposed to glyphosate, however, an increase in the expression of estrogen receptors mRNA in the testis was observed, suggesting a possible endocrine-disrupting effect. These results confirm Podarcis siculus as a highly sensitive biological model for studying the sublethal effects of soil contaminants on terrestrial vertebrates. The histological and molecular biomarkers detected are useful tools for environmental biomonitoring programs, improving the assessment of terrestrial ecosystem health and remediation effectiveness, also providing essential data for future ecotoxicological risk assessments.