Temperature limits to activity, feeding and metabolism in the Antarctic starfish Odontaster validus

Cold-blooded Antarctic marine species are highly stenothermal and possibly the most temperature-sensitive group on Earth. Studies to date have produced upper lethal temperatures in the range of 4 to 10 degrees C. Although invertebrates have not been acclimated to temperatures above 3 degrees C, some Antarctic fish have been acclimated to 4 degrees C. Activity competence has been evaluated in several Antarctic marine invertebrates and shown to be very sensitive to temperature, with 50% failures in the range of 1 to 3 degrees C for clams, limpets and scallops. The starfish Odontaster validus is much more capable of coping with elevated temperatures than any of these species. Turning speed increased with temperature, reaching a maximum at 7.5 degrees C. Temperature increase led to a clear hierarchy of response loss in the starfish, with lethal limits occurring at a higher temperature (15 degrees C) than loss of activity (9 degrees C) and loss of feeding competence (Specific Dynamic Action, or SDA) and coelomic oxygen level collapse both occurring at 6 degrees C. The higher temperature limit for activity than coelomic oxygen level could be explained by body design or taxonomic factors, which may also explain the markedly enhanced ability to cope with elevated temperature over other Antarctic marine species. Long-term acclimation and survival up to 6 degrees C should be possible for this species, which is important for species living on the west coast of the Antarctic Peninsula, possibly the fastest warming marine environment on Earth. The markedly higher resistance to elevated temperature and maintenance of function in a common Antarctic predator compared to the abilities of several of its prey species suggests that a warming environment could have dramatic consequences on the community-level ecological balance for large areas of the Antarctic benthos.

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