Effects of tidal emersion and marine heatwaves on cuttlefish early ontogeny

Anthropogenic climate change has increased the frequency and intensity of extreme weather events, such as marine heatwaves (MHW). They exert a strong influence over the structure and functioning of marine ecosystems, considering temperature is one of the most critical environmental factors affecting marine life. Additionally, intertidal habitats are ecologically challenging ecosystems, and inhabiting organisms need to possess the necessary mechanisms to adapt to the periodic fluctuations in physical characteristics across tidal cycles. To assess the effect of simulated MHWs (categories I and IV) and low tide conditions (emersion) on the early development of the common cuttlefish Sepia officinalis, the development time and hatching success were evaluated, as well as the antioxidant enzymatic machinery, lipid peroxidation, HSP70 and total ubiquitin concentrations. Embryonic development time decreased significantly with temperature, but tidal emersion held no significant impact on development time or hatching success. Superoxide dismutase activity levels were significantly increased with temperature but lowered under emersion conditions. Glutathione-S-transferase activity significantly increased with temperature, while glutathione peroxidase activity was significantly enhanced under emersion. Catalase activity, lipid peroxidation, HSP70 content and total ubiquitin content were not affected by any of the treatments. These findings suggest that while development time is greatly conditioned by temperature, S. officinalis embryos are remarkably resilient to emersion conditions. Moreover, the simulated marine heatwaves did not elicit any sub-lethal oxidative stress-related effects, suggesting that such temperatures were still within the optimum range of the cuttlefish thermal window of aerobic performance.