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Scientists at the Max Planck Institute for Chemical Ecology have used behavioral experiments to show that desert ants are able to quickly learn many food smells and memorize them for the rest of their lives. However, their memory of nesting odors seems to differ from that of their food smell: while food odors are learned and preserved after a single contact, ants need several attempts to memorize nest odors. In addition, ants quickly forget an odor associated with the nest after it has been removed from the nest. As a result, ants transform food and nest odors into their brain differently.
The desert ant Cataglyphis fortis has amazing abilities to trace food and return to its nest in the North African desert. Its sense of smell has a central function for orientation. The ant is not just a master browser, it is also an artist of memory. Markus Knaden behavior scientists at the Max Planck Institute for Chemical Ecology have been studying the navigation skills of this species of ant for years. Until now, he was particularly interested in the way in which small insects find their nest after an intensive search for food in the vast salines of the Tunisian Sahara. After all, the entrance to the nest is only a small, unobtrusive hole on the surface of the desert. He and his team have discovered that, in addition to other factors, the specific smell of the nest plays a crucial role. However, in their experiments, researchers had noticed that ants learned food odors much faster than nest odors. "Our central question was whether different types of memory existed for foraging and nesting. The idea of comparing the two learning processes emerged when we found that ants could learn incredibly fast food odors compared to nest odors that need to be trained much longer, "says first author, Roman Huber .
Scientists have developed a simple experiment to test the response of ants to over 30 different food odors. They were holding the end of a stick that had been scented with an odor about two meters from an ant on the ground, so that the wind was blowing the smell of the ant. At first, most odors were ignored by the ants and did not elicit any reaction. "After giving a crumb of food to the ants scented with one of these odors, the ants were almost always attracted by this smell," says Markus Knaden. "We were amazed at how quickly ants learned the odors associated with food and how long they could remember it. Even the ants, who had learned a smell more than 25 days ago, were able to remember it. In the wild, most ants have a short life and are usually killed by a predator within six days. Therefore, it is particularly surprising that ants having reached more than four times the average age can still remember what they have learned.
On the other hand, ants could not learn the odors associated with nests as quickly as food odors. When the researchers attached an odor to the nest entrance, the ants needed five to ten attempts to learn the odor as a benchmark. It is only after several trainings that they focused their nest search on this smell. When the odor was removed from the nest and the ants returned to the nest a few times, they completely stopped responding to the old landmark. In ants, odors are obviously treated differently in the brain, depending on whether they are food or nest signals.
Markus Knaden provides an explanation: "The two memories of different smells make sense. Throughout his life, an ant encounters many pieces of food while searching for food. As the insect finds its food primarily through olfactory cues, it is important for an ant to learn the smell of good food in order to look for it later. The nest, on the other hand, should always feel the same during the short life of an ant. As a result, no extraordinary memory is needed to locate the nest entrance following the olfactory cues. It's enough for an ant to know how much the nest felt when he went looking for food to find him at home. It is unlikely that the smell of the nest changes as an ant is looking for food. "
Scientists now want to design laboratory studies to support the results of behavioral experiments in the natural habitat of desert ants. Their goal is to use imaging techniques, such as calcium imaging, to locate and visualize the different memories in the ant brain and to compare brain activities during foraging and feeding. nest. "We already use similar techniques for visualizing brain activity in flies and mites. It would be good to establish these techniques also for ants, because ants have a particularly complex behavior, "says Markus Knaden.
Source:
Max Planck Institute for Chemical Ecology. .
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