Ocellus

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Overview

An ocellus (plural: ocelli) is a type of photoreceptor organ in animals. Also called "simple eyes", ocelli are miniature eyes capable of sensing light but not distinguishing its direction. See also stemmata, which are structurally similar. Ocelli are found in many invertebrates. Insects in particular have two types of ocelli, dorsal ocelli and lateral ocelli.

Photoreceptors

In insects, ocelli are involved (along with compound eyes) in the horizon-detecting response, decreasing the latency between horizon changes and the insect's response.

Dorsal Ocelli

Dorsal ocelli are light-sensitive organs on the dorsal surface or on the top of the head. There are generally three, forming a triangle.

They consist of a few dozen rod cells covered with a corneal lens. In some species, such as locusts, dorsal ocelli may contain several hundreds of retinula cells. Insects with dorsal ocelli also have compound eyes.

Lateral Ocelli

Lateral ocelli have a mixture of rod cells and cone cells and are found on the sides of the head, one to six on each side.

Lateral ocelli are the only eyes of the larvae of several orders of insects (fleas, springtails, silverfish, and Strepsiptera).

External links

• John R. Meyer, Photoreceptorsde:Ocellus

fr:Ocelle (œil) nl:Ocellus no:Medianøye

Acknowledgement and Attribution Regarding Sources of Content

Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .