Life in the margins: the effect of immersion/emersion and tidal cycle on the North Atlantic limpet Patella vulgata protein synthesis rates.

Biological processes in intertidal species follow tidal rhythms that enhance survival and fitness. Whereas tidal effects on behaviour and metabolic rates have been widely studied, impacts on other key process such as protein synthesis are still poorly understood. To date, no studies have examined the effect of immersion/emersion and tidal cycles on protein synthesis rates (k). Patella vulgata is an intertidal limpet present in North-Eastern Atlantic rocky shores from high to low shore. Previously reported P. vulgata respiration and heart rate measurements suggest aerobic metabolism is maintained during emersion and growth rates increase from high to low shore, but whether these patterns are reflected in k is currently unclear. Here, we measured for the first time in any intertidal organism, k, RNA to protein ratios and RNA translational efficiency (k) in P. vulgata over a full tidal cycle, at three different shore heights. k increased during emersion (p < 0.001) and was significantly higher in low shore animals compared to the other shore heights (p < 0.001), additionally k was negatively correlated to body mass (p = 0.002). RNA to protein ratios remained unchanged over the tidal cycle (p = 0.659) and did not vary with shore height (p = 0.591). k was significantly higher during emersion and was also higher in low shore limpets (p < 0.001). This study demonstrates that P. vulgata increases k during emersion, an important adaptation in a species that spends a considerable amount of its lifecycle emersed. Intertidal species are highly exposed to increasing air temperatures, making knowledge of physiological responses during emersion critical in understanding and forecasting climate warming impacts.