The European eel Anguilla Anguilla Linne, 1758 has for a long time been of interest to naturalists (Aristotle, 350 BC) on account of its peculiar life cycle. It often appeared mysteriously and a large number of fanciful explanations have been expressed. It still intrigues biologists on account of its behavioural characteristics: its life span, its transatlantic migration, its nocturnal activity, its metamorphosis, as shown by the large number of papers published on the subject. Even Sigmund Freud (1877) looked into the problem of the sex differenciation in eels!