Intertidal encapsulated embryos exposed to environmental stressors associated with the tidal cycle: A study based on oxidative stress and antioxidant response in early stages of the muricid snail Acanthina monodon.

Intertidal environments are highly dynamic, exposing organisms to multiple physical stressors simultaneously. This study evaluates the physiological responses of encapsulated Acanthina monodon embryos to stressors associated with tidal cycles, using oxidative damage and antioxidant activity as indicators. Egg capsules collected from the rocky intertidal zone were subjected to a tidal cycle including 3 h of emersion followed by re-immersion. Environmental variables such as temperature, humidity, PAR and UV-B radiation were recorded. Samples were analyzed for lipid peroxidation, protein carbonyls, and total antioxidant capacity. Previous studies have shown that initial-stage embryos are particularly vulnerable to desiccation and thermal stress, yet little is known about their antioxidant responses under natural tidal fluctuations. Based on this, we hypothesize that embryos possess a developmentally regulated and environmentally responsive antioxidant defense system envolving an enzymes or non-enzymatic antioxidants that mitigates oxidative damage during emersion and activates repair mechanisms upon re-immersion. Results showed that early-stage embryos exhibited high antioxidant capacity, particularly during air exposure, suggesting an adaptive response to oxidative stress. Prolonged emersion increased oxidative damage markers, while re-immersion reduced them, indicating activation of repair mechanisms. No mortality was observed in any developmental stage. These findings support the hypothesis and highlight antioxidant capacity as a key strategy for survival during early ontogeny in fluctuating intertidal conditions. This study provides insight into the defense mechanisms of A. monodon embryos and their resilience to environmental stress during encapsulated development.