Physiology: Animal Function and Reproduction

Animal Senses

What are the three types of photoreceptors among invertebrates?

The three different types of eyes are represented by different types of photoreceptors among invertebrates. They are: 1) eye cup, 2) compound eye, and 3) single-lens eye. The eye cup is a cluster of photoreceptor cells that partially shield adjacent photoreceptor cells. The compound eye consists of many tiny light detectors (photoreceptors). Cray-fish, crabs, and nearly all insects have compound eyes. Single-lens eyes, found in cephalopods such as squids and octopi, are similar to cameras. They have a small opening, the pupil, through which light enters.


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