"Ocellus" redirects here. For the light-sensitive structure in dinoflagellates, see Ocelloid. For other uses, see Ocellus (disambiguation).
"Ocellation" redirects here. Not to be confused with Oscillation.
"Ocelli" redirects here. For the eye-like marking, see Eyespot (mimicry).
Head of Polistes with two compound eyes and three ocelli (circled)
A simple eye or ocellus (sometimes called a pigment pit[1][2]) refers to a form of eye or an optical arrangement composed of a single lens without an elaborate retina as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-lensed "compound eye", and is not necessarily at all simple in the usual sense of the word.
The structure of an animal's eye is determined by the environment in which it lives, and the behavioural tasks it must fulfill to survive. Arthropods differ widely in the habitats in which they live, as well as their visual requirements for finding food or conspecifics, and avoiding predators. Consequently, an enormous variety of eye types are found in arthropods to overcome visual problems or limitations.
Use of the term simple eye is flexible, and must be interpreted in proper context; for example, the eyes of most large animals are camera eyes and are sometimes considered "simple" because a single lens collects and focuses an entire image onto the retina (analogous to a camera). By other criteria, the presence of a complex retina distinguishes the vertebrate camera eye from the simple stemma or ommatidia which make up compound eyes. Additionally, not all invertebrate ocelli and ommatidium have simple photoreceptors. Many have various forms of retinula (a retina-like cluster of photoreceptor cells), including the ommatidia of most insects and the central eyes of camel spiders. Jumping spiders and some other predatory spiders with seemingly simple eyes also emulate retinal vision in various ways. Many insects have unambiguously compound eyes consisting of multiple lenses (up to tens of thousands), but achieve an effect similar to that of a camera eye, in that each ommatidium lens focuses light onto a number of neighbouring retinulae.
^"Catalog - Mendeley". www.mendeley.com. Archived from the original on 24 March 2012. Retrieved 4 May 2018.
^O'Connor M, Nilsson DE, Garm A (March 2010). "Temporal properties of the lens eyes of the box jellyfish Tripedalia cystophora". J. Comp. Physiol. A. 196 (3): 213–20. doi:10.1007/s00359-010-0506-8. PMC 2825319. PMID 20131056.
and 28 Related for: Simple eye in invertebrates information
occurs in most vertebrates. In this sense "simpleeye" is distinct from a multi-lensed "compound eye", and is not necessarily at all simplein the usual...
compound eyes. Arthropod eye Mollusc eyeSimpleeyeininvertebrates Vision in fish Eakin, R. M (1973). The Third Eye. Berkeley: University of California...
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in their structure, arrangement, and function. They usually have eight, each being a simpleeye with a single lens rather than multiple units as in the...
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into the eye. They also have a high number of rods in their retina that are sensitive to dim light. While these improve the ability to see in darkness...
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naked eye 'tis evident that the stem or quill of each Feather in the tail sends out multitudes of Lateral branches, ... so each of those threads in the...
eye attractive to study because the eye distinctively exemplifies an analogous organ found in many animal forms. Simple light detection is found in bacteria...
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of an animal are derived from the embryonic germ layers. Those simplerinvertebrates which are formed from two germ layers of ectoderm and endoderm are...
origins of the anatomical features of the eye. One likely chain of development is that the eyes originated as simple patches of photoreceptor cells that could...
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last step in the integration of the aggregate of simple ocelli into a compound eye, and of further integration of a compound eye into a simpleeye. Lateral...
and G proteins in the fan worm's eyes, which were previously only seen insimple ciliary photoreceptors in the brains of some invertebrates, as opposed to...
jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including...
They feed primarily on algae, but will occasionally consume sessile invertebrates (including crustaceans, worms, and molluscs). They are considered commercially...
each eye for visual processing. Cephalopods such as the octopus and squid have the largest brains of any invertebrates. There are several invertebrate species...
John E. (2014). "Order Ephemeroptera". In Thorp; Rogers (eds.). Thorp and Covich's Freshwater Invertebrates (4th ed.). Academic Press. pp. 873–891. Hauer...
Wanninger, Andreas (11 August 2015). Evolutionary Developmental Biology of Invertebrates 6: Deuterostomia. Springer. pp. 93–94, 108–109. ISBN 978-3-7091-1856-6...
hagfish as elementary vertebrates in between invertebrates and gnathostomes. However, discussion has long occurred in scientific literature about whether...
prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the tropical coral reef environment. A...
Box jellyfish (class Cubozoa) are cnidarian invertebrates distinguished by their box-like (i.e. cube-shaped) body. Some species of box jellyfish produce...
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