Slow growers: A spawning aggregation of Antarctic limpets (Nacella concinna). New research hints that limpets and other cold-blooded polar species synthesise protein inefficiently and may find it difficult to compete with invading species as the climate changes.

Credit: BAS

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SYDNEY: A new study hints that animals at the poles may have less efficient metabolisms than their warm water counterparts, and that they may find it difficult to compete as the climate changes.

Previous research suggested that a dearth of food in winter was the major factor leading to slow rates of growth in cold-blooded polar animals. But a study of an invertebrate now suggests that the frigid temperatures prevent them from efficiently synthesising proteins – which are the building blocks of growth and countless celullar processes.

"Big implications"

"Making proteins is one of the most expensive things an animal does, therefore inefficiencies in this process have big implications for the energy costs of growth", said Keiron Fraser, lead author of the study and marine ecophysiologist with the British Antarctic Survey (BAS) team and the University of Cambridge in England.

Fraser's team believe that results of their study on the limpet, Nacella concinna – a shelled invertebrate found clamped to marine rock surfaces – may also apply to other cold-blooded animals such as fish and other molluscs.

The BAS team studied the growth rates of limpets at a variety of ocean temperatures in the laboratory and in their natural habitat – up to 13 m below the icy-cold water surface. As they reveal in the current Journal of Experimental Biology they found that their was no difference in feeding levels throughout the year in wild limpets, leading them to finger an inefficient metabolism as the cause of low growth rates.

The researchers further found that Antarctic limpets retain as little as 20 per cent of the proteins they synthesise, compared to up to 70 per cent in tropical species of limpets.

Unexpected discovery

The laboratory experiments also led to an unexpected discovery; that a small shift in temperature of just one to two °C above the typical summer maximum lead to a further drop in efficiency of protein synthesis.

Their findings suggest that as water temperatures increase along with global warming, cold-blooded Antarctic species may grow even more slowly and find it near impossible to compete with invading warm-water species taking advantage of the balmier conditions.

"Antarctic animals… may be incapable of competing with invasive species from outside which are likely to grow more efficiently [as temperatures warm]," said Fraser.

"The work raises further questions as to whether Antarctic ectotherms [cold-blooded animals] will be able to respond, or indeed compensate, for the predicted increases in Antarctic temperatures – or whether their thermal sensitivities will limit their growth and survival", commented zoologist Nia Whitely at the U.K.'s University of Wales in Bangor.