How a tree ants leads to slavery
Acacia needs defenders or against herbivores that thorns do not frighten or against plants that are growing too close to him . Defender , so this is the role that ants have endorsed in exchange for food and shelter . The living consists of sweet nectar and tiny nodules rich in protein and fat while covered materializes by needlethorn where insects settle their colonies. For their part, the ants attack mercilessly herbivores who want to feed the plant and are a formidable effectiveness in Africa , even the elephants away a species of acacia as they fear biting ants protect it !
The case of a Central American acacia , acacia ox horn seems even more refined . His host , the ant Pseudomyrmex ferrugineus , is indeed affected a small digestive deficiency . Adult, it almost does not secrete the enzyme invertase , which breaks the sucrose molecule ( which includes the commercial sugar ) into two smaller molecules , a glucose and fructose from which they are then treated easily by the body. In other words , this ant does not digest table sugar . Well, the plant grows so kind to synthesize itself invertase and therefore offers its nectar as fructose and glucose, its insect - tenant advocates can eat without a problem.
Beautiful? Not so simple. A team of German and Mexican researchers were intrigued by the fact that evolution has led this ant to "lose" invertase , while it happens, when it attacks the neighboring plants to be in contact with honey or sweet sap . Why miss this easy source of sugars ? Their suspicions were aroused when they noticed that the ant larvae normally produced invertase and they asked the following question: if the acacia was not as helpful as it might seem at first glance ? And if manipulating the metabolism of the adult ant to prevent synthesizing enzyme and retain prisoner?
In their fascinating study , published Nov. 4 in Ecology Letters , the researchers not only confirmed that the larvae secrete invertase well but if insects leaving the larval state could , if we offered them as the first adult meal sucrose syrup , digest with no problem. However, if the acacia nectar was on the menu of the first meal , the ant refused thereafter sugar water , as if she had become " addicted " to the nectar. The reality is diabolical in this famous nectar is another enzyme, chitinase , which , by a mechanism that remains to be clarified , inhibits the production of invertase in the ant and thus makes intolerant to sucrose.
Section of Ecology Letters says: " Once the young worker is fed nectar, its rate decreases invertase , it begins to select a diet without sucrose and , therefore, continues to feed on the nectar without sucrose , thereby enhancing the inhibition of invertase . " In short, when the mechanism is launched , nothing stops . And, as the researchers point out , as there is every chance for his first adult meal , ant " is feeding on nectar or receives from its nest mates through social feeding " acacia holds insects in its grip . Ants are as enslaved , forced to remain on the tree under penalty penalty starve. Similarly , they have doubled interest in defending the plant because his death would mean their death. Symbiosis certainly exists but is forced.
As explained by the National Geographic Martin Heil , the first author of this study, " it was a surprise for me to see that the stationary plant, " passive " could manipulate his partner any more active Clearly, the ant " . German researcher adds that this discovery could change the way biologists consider the phenomenon of mutualism : " The manipulation of partner could play a role in several different types of mutualism . " It must indeed little to disrupt the balance and spend an association win-win outright exploitation ...
Pierre Barthélémy ( follow me on Twitter here or on Facebook here )
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