ocellus

References

ocellus

anatomy

Also known as: ocelli

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Last updated

July 1, 2026

Quick Summary

An ocellus is a small, simple eye or eyespot found in invertebrates. In insects, ocelli are one of two types of eyes, the other being compound eyes. These simple eyes are capable of detecting light, darkness, and movement, but they provide a crude visual image due to their primitive optical structure. The term "ocellar" relates to or connects with an ocellus. Ocelli are derived from the epidermis and connect to the brain via sensory axons.123

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- nervous system
  Simple bilateral systems
  The eyes, or ocelli, may occur as a pair situated anteriorly or may be scattered abundantly over the head region depending on the species. Short optic nerves connect the eyes with the brain.
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  The eyes, or ocelli, may occur as a pair situated anteriorly or may be scattered abundantly over the head region depending on the species. Short optic nerves connect the eyes with the brain.
  Read More

cnidarian
Nervous system and organs of sensation
Light-sensitive ocelli (external patches of pigment and photoreceptor cells organized in either a flat disk or a pit) occur in some medusae of each of the three classes that possess this stage. Such sensory structures are closely associated with a nerve net.
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Light-sensitive ocelli (external patches of pigment and photoreceptor cells organized in either a flat disk or a pit) occur in some medusae of each of the three classes that possess this stage. Such sensory structures are closely associated with a nerve net.
Read More