From hydrothermal vents on the ocean floor to the deserts on all five continents: Life thrives even in the hottest places on our planet. Evolution has produced adaptation strategies that are as diverse as they are astonishing. We present ten organisms and their tactics for dealing with heat.
In the hot, dry regions of Australia, the short-beaked echidna (Tachyglossus aculeatus) knows how to stay cool. The egg-laying mammal blows mucus bubbles out of its beak, which is filled with blood vessels, and cools itself by means of the resulting evaporation chill. When needed, it also raises its insulating spines in order to dissipate even more heat through the interjacent skin.
Shimmering heat wherever you look – salt pans are inhospitable places. So it is important to have a cool refuge that you never lose sight of. To this end, the North African species of desert ant known as Cataglyphis fortis builds a hill over its underground nest that can be seen from far and wide. This helps the worker ants foraging for food to quickly find their way home, because every second too long under the burning sun could be fatal.
Tardigrades can be found in almost every kind of damp habitat and are masters at defying extreme environmental conditions – especially in “sleep mode,” when they lose about 90 percent of their body water and practically become mummies. In this state, some species like Viridiscus viridianus can survive temperatures of up to 95°C. Researchers still have many unanswered questions about how exactly the small invertebrates come through this experience unharmed.
Rüppell’s sand fox (Vulpes rueppellii) generally hunts at dusk or at night and takes it easy during the day. Its body is built for the hot deserts of North Africa. The small fox not only radiates off a lot of heat through its large body surface area compared to its volume, but also through its large ears. And instead of drinking, it gets the fluids its needs from its prey.
Snails in the desert? Yes, there are! Snails in the Sphincterochilidae family are adapted to hot, arid habitats and only become active during rare periods of precipitation. Otherwise, they live withdrawn in their chalky-white shell, which reflects most of the sun’s rays. In addition, the creatures burrow underground and estivate (the summer equivalent of hibernation) during the time of the year when least food is available.
It is said that grabbing on to panic grass (Dichanthelium lanuginosum) has saved some folk from a (very!) hot bath. The North American grass species is found on the shores of hot springs or geysers and can grow in soil temperatures of up to 65°C. But it takes three for this to work: The plant hosts a fungus, which in turn is infected with an RNA virus. While the plant roots enclose the fungus and virus in a protective envelope, the latter two jointly increase the grass’s tolerance to heat stress at the molecular level.
Like all cold-blooded reptiles, the North African mastigure (Uromastyx acanthinura) is completely reliant on the sun’s warmth to return to ‘operating temperature’ after a cold desert night. So as not to dangerously overheat during the day, the lizard makes yellow skin patches appear on its previously dark back, thus making itself brighter. During the most intense midday heat, it also seeks refuge in its cool burrow deep underground.
Pyrolobus fumarii is a species of archaea that feels comfortable at temperatures of around 100°C – just ten degrees lower and it gets too cold for them. To survive at such temperatures, the single-celled creature is equipped with extremely thermostable proteins, metabolites, and DNA. It lives in hydrothermal vents on the ocean floor, where water remains liquid at over 100°C due to the high pressure.
The red alga Galdieria sulphuraria lives in hot, sulfurous, and acidic volcanic springs, such as the ones in Yellowstone National Park. It accessed this extreme habitat by means of horizontal gene transfer – that is to say, by importing useful genes from extremophile archaea and bacteria. This is a very unusual type of genetic adaptation – especially for eukaryotes, organisms with a cell nucleus.
The body temperature of a dromedary (Camelus dromedarius) can fluctuate between 42°C during the day and 34°C in cold desert nights – in human terms, this is the difference between high fever and hypothermia. This tolerance allows the ungulates to give off stored-up heat during the night and start fresh into the day the next morning. In the daytime, this strategy reduces the need to sweat and thus saves water.
Extreme LMU research:
Geobiologist William Orsi
explores life at the bottom of the deep ocean – including archaea.
Botanist Julia Bechteler
studies plants that defy the heat and lack of water in the desert.
Biogeochemist Gonzalo Gomez-Saez
researches how microbial communities respond to temperature changes.
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