It smells like a stable! Everyone knows this expression that suggests that a horse, when approaching its home, shows a special excitement. The study published on Tuesday, September 17 in the journal Frontiers in marine sciences It does not say whether the mysids kick or change their behaviour near their cave. But one thing is certain: these crustaceans, a kind of tiny shrimp measuring about five millimetres, recognise the chemical landscape around them and show a certain preference for the water in their cave. home Sweet Home.
It must be said that caves play an essential role in the lives of these creatures. Preyed upon by a large number of fish and other crustaceans, they find in darkness an essential protection during the day. But this same darkness, which prevents any photosynthesis, is not a matter of finding the algae, plankton and other plant remains that are their delight. Moreover, every evening, the swarm, made up of millions of individuals, leaves its lair. And at dawn, satisfied, it returns home.
Finding the way out of the cave is not a problem: you just have to follow the light. But finding the entrance seems much more complex. The Marseille coves where the last study was carried out contain numerous cavities, which at first glance are quite similar. However, the mysids do not seem to make any mistakes in their daily migration. So how do they guide themselves?
“A royal signature”
Thierry Perez’s team at the Endoume marine station in Marseille, which specialises in studying this particular ecosystem of underwater caves, observed for the first time that, despite appearances, each one concealed a particular chemical profile. The systematic analysis of the molecules present in the water revealed hundreds of different signals. What to do for each cavity. “a royal signature”the environmentalist estimates.
Mysids do not make mistakes. This is the main result of this research. To test it, the Marseille researchers set up an experiment that was, in principle, quite simple. Hundreds of individuals were taken from two caves neighbouring the coves, Jarre and Fauconnière. Then, one by one, they were placed in a Y-shaped device that allowed them to choose between two waters, “their own”, from which they were extracted, and another. And the result is clear: if the crustaceans, visibly curious, try both arms of the device, they spend much more time in the one that houses their original environment. Their way of choosing. The researchers carried out the same experiment with leptomycessmall shrimps that live, again, in the streams, but outside the caves. This time no preference was observed.
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