Periodic moulting is needed for crayfish to be able to grow blickwinkel / Alamy Stock Photo

WHEN a crayfish sheds its protective exoskeleton, it becomes temporarily vulnerable to attack by predators. Now there is evidence that this leads to behaviour that resembles anxiety, and that this can be relieved using the same anti-anxiety drugs that humans take.

“They worry, they have an apprehension state that makes them avoid potentially dangerous areas. It’s kind of like a primitive anxiety,” says Pascal Fossat at the University of Bordeaux in France.

Fossat and his colleagues collected crayfish from swamps near Bordeaux and …