Ecological Indicators (Aug 2024)
Aging in animals – Individuals decline and the impacts on toxicity – Hazard of Cd in Enchytraeus crypticus
Abstract
Aging is a natural process for all living beings and there is often a decline of overall performance after a certain age tipping point. The response to stressors, e.g. exposure to chemicals can differ depending on the individuals’ age. Standard guidelines do not always include synchronized age animals and are often optimized based on healthy animals of homogeneous populations, not aiming to cover age aspects. Hence, in the present study we aimed to assess the effects of aging on Enchytraeus crypticus (Oligochaeta) response to cadmium (Cd) exposure. For that, cultures with 3 synchronized ages [young: 18–20 days old, old: 91–93 days old and oldest: 127–129 days old] plus the standard (non-synchronized adults), were exposed to CdCl2 (0, 1, 3.2, 10, 32, 100, 320 mg Cd/kg) in LUFA 2.2 soil. Results showed that Cd toxicity varied depending on the animal’s age, with the young and oldest being most sensitive to Cd (reproduction EC50_old = 138 > EC50_young = 69 > EC50_oldest = 46 mg Cd/kg soil). This highlights the importance of age when assessing toxicity. Testing animals with synchronized age should improve results comparability but will not necessarily capture the most sensitive age. Toxicity to Cd has been shown to be higher in younger animals compared to standard cultures, although this may not be a general pattern with other chemicals or stressors. When using standardized guidelines, if cultures are not synchronized results will suffer from variability due to various ages of the animals. For a standard context we recommend the start with young (18–20 days) animals instead of non-synchronized adults. On the other hand, the study of populations on the edge windo w is highly relevant and can be much more explored in an ecotoxicology frame, as this can also enlighten impacts of aging in a wider species context.
