Adaptations to thermal variation in two Mediterranean limpets - cardiac response and haemocyte lysosomal stability

Patella rustica and Patella caerulea are two congeneric limpet species, both occurring along the rocky shores of the Mediterranean but on different tidal heights. P. rustica is dominant in the upper intertidal zone while P. caerulea is more abundant in the lower part of the same zone. Understanding variations in physiological adaptations to thermal stress is vital when investigating intertidal species' distribution. Hence, to investigate the relationship between their physiological thermal tolerance and intertidal zonation, laboratory experiments were designed to test the hypothesis that the lower zoned P. caerulea has reduced upper thermal limits when compared with higher zoned P. rustica, which is predicted to be more tolerant. Arrhenius break temperatures (ABTs) of cardiac performance were used as a sensitive parameter to estimate species critical thermal limits, together with analysis of haemocyte lysosomal stability, and both in line with the concept of oxygen and capacity - limited thermal tolerance