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Run for your life: the Saharan silver ant

Posted by on October 1, 2013

Saharan silver ant Cataclyphic bombycinaGuest post by Mel Evans, a student at the University of Gloucestershire. Read carefully – hidden in here is an answer to one of the pub quiz questions which will be asked during Professor Adam Hart’s 24 hour lecture

On the surface, ants don’t always seem like the most extreme of animals. Not so with the Saharan silver ant (Cataglyphis bombycina). This species races for its life every day to survive the scorching effects of the sun in North Africa. Predation and heat exposure cause them to avoid the coolest and hottest hours, leaving just a ten-minute window in which to catch food.

This strategy affords them a unique niche in which other ant species cannot survive, let alone compete. The silver ants wait until the temperature reaches 46°C – a temperature which also signals predators like fringe toad lizards (Uma sp.) to seek shelter from the sun. At the same time scouts keep watch at the entrance to the nest, as the lizards like to build their burrows nearby. Then, when the coast looks clear, hundreds of ants dart from the nest in a desperate hunt for food.

As they sprint across the sand, searching for other insects which have already succumbed to heat stress, they rely on some major adaptations which enable exploitation of their desert environment.

First, possessing longer legs than other ant species keeps their bodies 4mm away from the sand, where the temperature drops by 7°C. They also adopt a quadrapedal gait, keeping their two front legs raised away from surface temperatures which can reach 70°C.

Second, they take advantage of vegetation, climbing to the top of plant stalks to pause and rid themselves of excess body heat, a trait which can cause them to run up the legs of human visitors to the area. Third, they are exceptionally fast, reaching speeds of 50cm or 100 body lengths a second, a feat unmatched in the animal kingdom, and equivalent to us running 280mph. This minimises their sun exposure while contributing to convective cooling.

Finally, they produce shock proteins which allow their cellular functions to continue. Amazingly they do this before venturing out, as the proteins would not have time to work if the response occurred once they left the nest.

With the highest thermotolerance of any species, they continue to forage until they reach the critical thermal maximum of 53°C, at which point they have seconds to seek refuge before dying. As you might expect, many ants do not make it back to the nest, but the risks are worth it, with those that survive returning with 15-20 times their own bodyweight in food during their six-day lifespan.

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