Jellyfish are animals that are part of the Cnidaria family. Most of them have bodies that are shaped like bells, and they also have various tentacles that are poisonous. Most of the jellyfish found in many parts of the world are translucent with many of them changing colors. With these properties, people usually assume that they glow in the dark. One good reason for this is that most people see these beautifully-colored jellyfish in aquariums that are placed in dark areas. With the light shining through their translucent bodies, most jellyfish appear to glow in the dark. Many people can relate to the fact that most public aquariums and aquatic display areas are situated in darkened rooms with strategically-placed lights to enhance the color and brightness of various water creatures, including jellyfish. With backlighting, for example, an aquarium full of jellyfish will be able to enhance the translucent color of the jellyfishes’ bodies, and this effect will literally make them seemingly to glow.
The glow from most jellyfish does not actually come from its actual body. Instead, its translucent body basically reflects any available light in a particular aquarium. Many jellyfish also change color. So with the light passing through their bodies, people will also see the change in color as if they are actually glowing. Without a source of light, most jellyfish actually do not glow.
There is one type or class of jellyfish, though, that literally glows in the dark. Known as the Aequorea type of jellyfish, these animals are able to display their bioluminescent or phosphorescent properties. Through the mixing of two molecular proteins, this class of jellyfish is able to emit a green glow coming from their bodies. This particular class of jellyfish is not commonly found, and the glowing jellyfish that people usually see are those with translucent bodies.