Compound eye
Compound eyes consist of many photoreceptor units or ommatidia. Each 'ommatidium' (singular) is an individual 'eye unit'.
The image perceived is a combination of inputs from ommatidia on a convex surface. Thus they point in slightly different directions.
Compared with simple eyes, compound eyes possess a wide-angle view. They can detect fast movement and, in some cases, the polarization of light.[1]
The general picture
Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system.[2] Image-resolving eyes are present in molluscs, chordates and arthropods.[3]
Almost all insects and arachnids use both simple and compound eyes.
Types of compound eye
Compound eyes fall into two groups: apposition eyes, which form multiple inverted images, and superposition eyes, which form a single erect image.[4] Compound eyes are common in arthropods, and are also present in annelids and some bivalved molluscs.[5]
Compound eyes, in arthropods at least, grow at their margins by the addition of new ommatidia.[6]
Good fliers
Good fliers like flies or honey bees, or prey-catching insects like praying mantis or dragonflies, have specialized zones of ommatidia organized into a foveal area which gives acute vision. In the acute zone the eyes are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution.
Other types
Another version is the pseudofaceted eye, as seen in Scutigera. This type of eye consists of a cluster of numerous ocelli on each side of the head, organized in a way that resembles a true compound eye.
The body of Ophiocoma wendtii, a type of brittle star, is covered with ommatidia, turning its whole skin into a compound eye. The same is true of many chitons.
Compound Eye Media
Compound eye of Antarctic krill as imaged by an electron microscope
Head of a mantisfly showing a compound eye
Compound eye of a dragonfly
References
- ↑ Völkel R; Eisner M. & Weible K.J.. Miniaturized imaging systems. Microelectronic Engineering 67-68 (1) (2003). p. 461–472. doi:10.1016/S0167-9317(03)00102-3. Retrieved 2011-01-17.
- ↑ Land, M.F.. The evolution of eyes. Annual Review of Neuroscience 15 (1992). p. 1–29. doi:10.1146/annurev.ne.15.030192.000245.
- ↑ Frentiu, Francesca D.. A butterfly eye's view of birds. BioEssays 30 (11–12) (2008). p. 1151–62. doi:10.1002/bies.20828.
- ↑ Gaten, Edward. Optics and phylogeny: is there an insight? The evolution of superposition eyes in the Decapoda (Crustacea). Contributions to Zoology 67 (4) (1998). p. 223–236. doi:10.1163/18759866-06704001. Retrieved 2011-01-17.
- ↑ Ritchie, Alexander. 'Ainiktozoon loganense Scourfield, a protochordate? from the Silurian of Scotland. Alcheringa 9 (2) (1985). p. 137. doi:10.1080/03115518508618961.
- ↑ Mayer, G.. Structure and development of onychophoran eyes: What is the ancestral visual organ in arthropods?. Arthropod Structure and Development 35 (4) (2006). p. 231–245. doi:10.1016/j.asd.2006.06.003.