Differential anoxia and hypoxia tolerance in two color morphs of the green crab, Carcinus maenas

Abstract

Despite the name green crab, Carcinus maenas displays red and green color morphs. Earlier studies using organismic parameters suggest differences in stress tolerance between the color morphs without a detailed study on their cellular physiology. We tested the hypothesis that the differential stress tolerance at the organismic level is reflected in a difference in cellular stress parameters during anoxia and hypoxia. Crabs of both color morphs were exposed to 2 h anoxia or up to 24 h hypoxia. For organismic parameters, we analyzed righting response, heart rate, oxygen consumption, and running endurance on a treadmill. At the cellular level, we measured heart tissue lactate accumulation, AMP‐activated protein kinase (AMPK) activity and mRNA expression, and heat shock protein (HSP70) levels and mRNA expression. At the organismic level, color morphs showed no differences during normoxia and anoxia. Only during hypoxia did green morphs perform better. At the cellular level green morphs showed elevated levels of stress parameters such as AMPK and HSP70, which contradicts earlier publications that describe green morphs as more stress tolerant. Our findings provide the first data of cellular differences between color morphs and question the assumption that green color morphs are generally more stress tolerant than red morphs. Funded by NSF‐IOB 0640478 to MF and an APS summer fellowship to CAT.