Influence of maternal age on the effects of seleno-l-methionine in the model organism Daphnia pulex under standard and heat stress conditions.

Selenium deficiency and toxicity increase the risk of adverse developmental and reproductive outcomes; however, few multi-stressor studies have evaluated the influence of maternal age on organic selenium dose-response and additional stressors over the life course. While multi-stressor research in mammalian models is time-consuming and expensive, use of alternative models can efficiently produce screening data for prioritizing research in mammalian systems. As a well-known eco-toxicological model, Daphnia pulex, may offer advantages in screening for impacts of multi-stressor exposures. We evaluated the influence of maternal age on the effects of seleno-methionine (SeMet) for lifespan, reproduction, and heat-stress resistance in D. pulex. Our results show effects of SeMet-treatment and maternal age, where the highest SeMet-treatment had reduced lifespan and absence of reproduction, and where Daphnia from late life broods had increased resistance to heat-induced stress. Further analysis suggests an additional interactive effect between maternal age and SeMet treatment on time to first reproduction.