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

Abstract

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 hypothesized to reduce decapod activity, especially in combination with high magnesium levels in the hemolymph ([Mg2+]HL), as [Mg2+] has a relaxant effect. Mg2+ is abundant in seawater and in combination with polar temperatures causes a relaxant effect in Crustacea (Frederich et al. 2001). Because 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). In contrast, caridean shrimp regulate [Mg2+]HL to very low levels. The combined effect of low temperatures and high [Mg2+]HL might explain the limits of cold tolerance in decapods and has been put forward as the principal reason for the absence of crabs and lobsters from the high‐polar regions (Frederich et al. 2001, Aronson et al. 2015a). These large, benthic, shell‐crushing decapods, along with shell‐crushing teleosts and elasmobranchs, are important in structuring benthic communities at lower latitudes.

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