The parasite of a species of ants considerably slows down their aging, but this is undoubtedly to facilitate their ingestion by a bird, in which the intruder will complete its growth, indicates a study published on May 19.
An extended life expectancy
“We have monitored the survival of insects at three years and we show that infected ants live much longer than uninfected“, Susanne Foitzik, professor of biology at the German University of Mainz, told AFP. And that’s an understatement, since no healthy ants have passed this milestone, while more than half of the parasitized ants were still alive, according to the study published in Royal Society Open Science.
Temnothorax nylanderi (T. nylanderi), also called acorn ant, where it makes a small nest, is a widespread species in Western Europe. Entomologists have long known that their working caste is the prime target of a parasite, theAnomotaenla short (A. brief). In adulthood, this small worm, a tapeworm cespode, lives in the digestive tract of the woodpecker. It lays eggs there which are found in the droppings of the bird, before appearing on the menu of the larvae of T. nylanderi. The parasite’s eggs then colonize their hemolymph (the ant’s “blood”) and develop there in the form of larvae.
Eternal youth
Infected ants seem to retain a form of eternal youth. Their cuticle, the exoskeleton serving as their shell and skin, retains the pale yellow color of young ants, initially confined to the nursery. The parasite also modifies their behavior since they refuse to follow the worker ants, which venture outside to feed the anthill. “Why can they live so long?“, with a survival rate identical to that of queens, some of which reach up to twenty years, wonders Professor Foitzik, who signed the study with his former student Sara Beros, now a researcher at the Institute. Max Planck. “Maybe thanks to more care“, car “infected ants receive more attention from other workers“, who seem attracted by a particular chemical signal from their exoskeleton. But the entomologist’s team also established, in another study published in January 2021, that the presence of the parasite”amplified the expression of genes linked to immunity, and to a lesser extent of genes linked to longevity“, says the biologist. In other words, the parasite would help the organism of the ant to fight against aging.
Better yet, Professor Foitzik’s team is analyzing the proteins released by the parasite in the “blood” of the ant, which “opens a window on the phenomenon of aging“. “We have found that several of these proteins have antioxidant properties.“, very useful for the immune system, she said, considering”possible that the parasite itself helps the ant live longer“. “Why would the parasite seek to lengthen the lifespan of its host?“Asks Pr. Foitzik. She answers it in the study by supposing that it is the best way for the parasite to reach its final host. Because the larva of the parasite can only transform into a worm by finding the tube. woodpecker digestive.
Other ant parasites lead them to a rapid suicide to achieve their ends. The small liver fluke, which begins its cycle in a snail, passes to the ant of the species Formica, and pushes its host to lose company every day with its congeners to perch on top of the grasses, in “the hope” of being grazed by a ruminant, final target of the parasite. Another little worm, Myrmeconema neotropicum, causes its host ant to raise its red abdomen in the air, the better to tempt a passing bird, its final host. Which brings us back to the woodpecker, which would have little chance of spotting T. nylanderi and its maximum size of 3 mm in a pile of leaves. Infected ants “stay sheltered in their nest in an acorn or a branch, right in the place that the woodpecker will open to feed on larvae“, according to the study. For the researchers, it is therefore likely that the behavioral changes observed in the infected workers predispose them to be worked by the bird.
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