Impacts of aging and injuries on Enchytraeus crypticus’ performance: standard tests and gene expression: a mechanistic approach

• Autor(a) principal: Costa, Joana Margarida Santos
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/39245
• topic: Stressed population; Injuries; Animal’s geing; Gene expression; Enchytraeus crypticus

The standard guidelines that are the basis for risk assessment are typically designed for healthy individuals and within homogeneous populations. However, natural populations are not homogeneous. There are animals of variable age and also physical condition (e.g., the presence of injuries or diseases) which influence their overall performance, including the response to other stressors such as chemical exposure. This is not considered in the standard guidelines, which can lead to an underestimation of risks. Among the several factors that can affect animals’ performance, the effects of aging and the presence of injuries were studied here, using the soil ecotoxicology model species Enchytraeus crypticus (Oligochaeta). Enchytraeids are important members of soil fauna and used in ecotoxicity tests for more than 50 years. Further, E. crypticus has a vast array of tools available (from the full life cycle test to several -omics: transcriptomics, proteomics, metabolomics) being advantageous in comparison to other model species. The main goal of this research was to provide understanding on the biology and toxicological response of stressed populations: injured and aged. It was shown that E. crypticus can overcome perforating wounds (using microneedles) without significant effects on their performance (survival and reproduction) over 42 days after wounding. The mechanism for wound closure probably involves the inhibition of Rho GTPase activity, as described for the nematode Caenorhabditis elegans, and confirmed here through the down-regulation of the Rho family GTPase 1 gene (Rho-1). These provide the base procedures for further studies on, for instance, the impacts of chemical exposure on injured animals. Cadmium (Cd) was used to investigate age related sensitivity differences, in animals with synchronized age (young: 18-20 days, old: 91-93, and oldest: 127- 129 days). It was shown that the toxicity of Cd to E. crypticus varied with animals’ age: was higher for young adults and increased with age (from old to oldest). This confirms the importance of testing with animals of synchronized age, which will exclude the age variability factor. Test procedures were provided to the assessment of impacts on a sensitive edge of the population – older animals. These can also be the base for further research on the mechanisms involved in aging and toxicity related responses. Studies that are conducted on vulnerable populations provide researchers a better understanding of the variable performances and mechanisms that can be expected in natural populations, where age or physical condition are not uniform.