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Concept
Ocelle (tache)
Résumé
An eyespot (sometimes ocellus) is an eye-like marking. They are found in butterflies, reptiles, cats, birds and fish.
Eyespots could be explained in at least three different ways. They may be a form of mimicry in which a spot on the body of an animal resembles an eye of a different animal, to deceive potential predator or prey species. They may be a form of self-mimicry, to draw a predator's attention away from the prey's most vulnerable body parts. Or they may serve to make the prey appear inedible or dangerous. Eyespot markings may play a role in intraspecies communication or courtship; the best-known example is probably the eyespots on a peacock's display feathers.
The pattern-forming biological process (morphogenesis) of eyespots in a wide variety of animals is controlled by a small number of genes active in embryonic development, including the genes called Engrailed, Distal-less, Hedgehog, Antennapedia, and the Notch signaling pathway.
Artificial eyespots have been shown to reduce predation of cattle by lions.
The eye-like markings in some butterflies and moths and certain other insects, as well as birds like the sunbittern, serve functions in addition to mimicry; indeed, it is unclear whether they actually mimic eyes. There is evidence that eyespots in butterflies are antipredator adaptations, either in deimatic displays to intimidate predators, or to deflect attacks away from vital body parts. In species such as Hipparchia semele, the conspicuous eyespots are hidden at rest to decrease detectability, and only exposed when they believe potential predators are nearby. Butterfly eyespots can mimic dead leaves for camouflage from predators, as seen in Bicyclus anynana; this is a response to a seasonal fall in temperature, causing a shift in selection towards smaller, less conspicuous eyespots among those individuals developing at that time. Butterfly eyespots may play a role in mate recognition and sexual selection. Sexual selection drives the diversification of eyespots in different species of butterflies, as mates select for characteristics like size and brightness.
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