Compared to their temperate and tropical cousins, cold-blooded polar marine animals are incapable of fast growth. Until now scientists assumed that a lack of food in winter was the major limiting factor. Studies of the protein-making abilities of limpets in both the sea around the British Antarctic Survey's (BAS) Rothera Research Station and in the laboratory aquarium reveal that these animals cannot make proteins -- the building blocks of growth - efficiently.

Lead author Dr Keiron Fraser from BAS says, "This is an important step forward in our understanding of the complex biodiversity of Antarctica's unique ecosystem. Sea temperature is predicted to increase by around 2°C in the next 100 years. If cold-blooded Antarctic animals can't grow efficiently, or increase their growth rates, they are unlikely to be able to cope in warmer water, or compete with species that will inevitably move into the region as temperatures rise."

Growth in animals occurs primarily by making and retaining proteins. While tropical water limpets typically retain 70% of the proteins they make, those in the Antarctic appear only to retain about 20%.

About Limpets

The Antarctic limpet (Nacella concinna) used in this study, is an extremely common shallow water species. In some areas hundreds of individuals can be found per square metre of seabed. This limpet forms an important part of the diets of many seabirds, fish and starfish.

To test if limpets could grow faster in warmer water BAS biologists compared the protein-making abilities of limpets in both the sea around the BAS Rothera Research Station, and in the laboratory aquarium. In the Antarctic summer of 1999 BAS SCUBA divers collected around 100 free-ranging limpets, numbered them with paint for identification, then weighed them before they were returned to the sea. Two months later the limpets were recovered and weighed, before their ability to make proteins was measured. In the following Antarctic winter the experimental work was repeated.

The ability of the limpets to make proteins at a range of water temperatures was also investigated also in the aquarium. The researchers found that even at artificially elevated water temperatures, the Antarctic limpet cannot increase the rate at which it makes proteins. In fact the synthesis rate decreases. Also, the proportion of newly made protein that the limpets manage to retain for growth is much less than in warmer water animals.

Reference: "Growth in the slow lane: protein metabolism in the Antarctic limpet Nacella concinna" (Strebel 1908) by Keiron Fraser, Andrew Clarke, and Lloyd Peck, is published in the Journal of Experimental Biology, 210, 2691-2699

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Materials provided by British Antarctic Survey. Note: Content may be edited for style and length.