Compound eye

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Compound eye

Scutigera coleoptrata left eye

File:DragonFly macrogiants E.jpg

DragonFly macrogiants

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Paper Wasp Head

Compound eye is a visual organ found in certain arthropods such as insects and crustaceans. It consists of up to several thousand light-sensitive, miniature structures called ommatidia. Each ommatidium is a functioning eye in itself, and together they give a broad field of view and excellent motion detection, at the expense of low resolution.

Structure

The compound eye is made up of many small, repeating units, the ommatidia. Each ommatidium consists of a lens, a cone, visual cells (usually eight), and pigment cells. The lens helps to focus light, while the cone and pigment cells prevent light from spreading between ommatidia.

Function

The compound eye is very good at detecting motion. Because each ommatidium is essentially an eye in itself, it can detect changes in the light that falls on it. If an object moves across the field of view, the ommatidia will detect this change in light intensity. This makes the compound eye excellent for detecting predators and for navigation.

Types of Compound Eyes

There are two types of compound eyes: apposition eyes and superposition eyes. Apposition eyes are the most common form in daytime-active insects, while superposition eyes are more common in nocturnal insects.

Evolution

The compound eye has evolved independently in several different lineages. It is believed to have first evolved in the ancestors of the modern arthropods, over 500 million years ago. The basic structure of the compound eye has remained relatively unchanged since then, although there have been many adaptations to suit different lifestyles and environments.

See Also

• Simple eye in invertebrates
• Vision in fish
• Vision in birds
• Vision in mammals