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The arthropods ancestrally possessed compound eyes, but the type and origin of this eye varies between groups, and some taxa have secondarily developed simple eyes. The organ's development through the lineage can be estimated by comparing groups that branched early, such as the velvet worm and horseshoe crab to the advanced eye condition found ...
The butterfly compound eye consists of multiple ommatidia, each of which consist of nine photoreceptor cells (numbered from R1–R9), and primary and secondary pigment cells. [5] Nymphalid butterflies have the simplest eye ommatidium structure, consisting of eight photoreceptor cells (R1–R8) and a tiny R9 cell organized into a different tier.
The optic(al) lobe of arthropods is a structure of the protocerebrum that sits behind the arthropod eye (mostly compound eyes) and is responsible for the processing of the visual information. It is made up of three layers: Lamina (ganglionaris) responsible for contrast enhancement through lateral inhibition Medulla
Arthropod eyes Head of a wasp with three ocelli (center), and compound eyes at the left and right. Most arthropods have sophisticated visual systems that include one or more usually both of compound eyes and pigment-cup ocelli ("little eyes"). In most cases, ocelli are only capable of detecting the direction from which light is coming, using ...
Compound eye of a house centipede Compound eye of a dragonfly. A compound eye is a visual organ found in arthropods such as insects and crustaceans.It may consist of thousands of ommatidia, [1] which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distinguish brightness and color.
The compound eyes of the arthropods are composed of many simple facets which, depending on anatomical detail, may give either a single pixelated image or multiple images per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors arranged hexagonally, which can give a full 360° field of vision.
The size and complexity of eyes in harvestmen roughly correlates with the amount of light available in its habitat. Evolutionary reduction of eyes appears to be caused by the early termination of eye development (paedomorphosis) in most species. Adults of those species thus have eyes that resemble embryonic or juvenile forms of their ancestors.
The movement of the eye is controlled by six distinct extraocular muscles, a superior, an inferior, a medial and a lateral rectus, as well as a superior and an inferior oblique. The superior ophthalmic vein is a sigmoidal vessel along the superior margin of the orbital canal that drains deoxygenated blood from surrounding musculature.