Jellyfish are aquatic invertebrates with gelatinous bodies and gelatinous tentacles. They have a variety of shapes, colors, and sizes. A jellyfish has no eyes but it does have a light-sensitive organ called the “nauplius”. The nauplius is located on the underside of the jellyfish’s body near its mouth. It is used for sensing light and movement in their environment.
Jellyfish have eight primitively simple eyes which are used for detecting light and motion. They mostly swim near the surface of the water, where they are close enough to sunlight to receive food particles that drift down from above.