Advances in ecotoxicological research using planarians: a comprehensive review

Planarians, distinguished by their extraordinary regenerative capacity and ecological role as benthic predators, have emerged as a transformative model in ecotoxicology. This review provides a comprehensive synthesis of research on the effects of diverse classes of pollutants, including metals, pesticides, pharmaceuticals, personal care products, nanomaterials, and a dedicated category of "other pollutants," namely biotoxins and physical stressors, on these organisms. We introduce a novel conceptual framework of "regenerative toxicology," which focuses on how contaminants impair an organism's innate self-repair mechanisms. Our analysis reveals a convergent toxicity pattern: despite differing initial targets, most pollutants induced oxidative stress, which triggered cellular responses, including apoptosis, ultimately disrupting neoblast function and leading to failures in regeneration, behavior, and reproduction. A key advancement of this study is its emphasis on ecological realism and complex exposure scenarios. We critically evaluate the sensitivity of planarians to real-world environmental samples and highlight the significant implications of combined toxicity, such as the "Trojan horse" effect, in which microplastics increase the bioavailability of co-pollutants such as metals. This review further integrates methodological innovations, from multi-endpoint behavioral assays to multi-omics and AI-driven predictive modelling, while underscoring the urgent need for standardization in culture and testing methods. By bridging molecular mechanisms with individual and potential population-level outcomes, the planarian model offers a unique, cost-effective platform for assessing the sublethal and long-term hazards of environmental pollution. This review establishes planarians as an indispensable tool for elucidating the consequences of contaminants on tissue homeostasis and ecosystem health, thereby informing more robust environmental risk assessments.