From deep to shallow seas: Antarctic king crab on the move

The fauna of decapod crustaceans in the Southern Ocean has historically been considered impoverished, with only about a dozen species of decapod shrimp overall, of which only three species are common and abundant on the Antarctic continental shelf. Crabs and lobsters were assumed to be absent or very rare in the Southern Ocean, mainly ascribed to the physiological constraint of cold polar waters. Polar temperatures have been hypothesised to reduce decapod activity, especially in combination with high magnesium levels in the haemolymph ([Mg2+]HL), as [Mg2+] has a relaxant effect. Mg2+ is abundant in seawater and in combination with polar temperatures causes relaxant effect in Crustacea (Frederich et al., 2001). Since most crabs are capable of regulating [Mg2+]HL only slightly below the [Mg2+] of seawater, their ability to maintain activity should be hampered (Frederich et al., 2001, Aronson et al. 2015a)