The animal world's leading lights

This jellyfish commonly known as the mauve stinger starts lighting up once it is unsettled by forces like water turbulence. Experts refer to this response as bioluminescence - the ability to generate light either on one's own or with the help of bacteria. The phenomenon is most often seen among aquatic animals.

Single-celled organisms, like this dinoflagellate, are also capable of producing light. Their light is unleashed when strong waves or fish swimming quickly by cause deformations in their cellular membranes. Their luminescence helps to confuse possible predators.

Of course, no list of glowing creatures could be complete without the firefly. Their light-emitting organs, known as photophores, produce the substance luciferin, which then reacts to oxygen. The reaction is what produces light. And humans aren't the only ones dazzled by the sight - male and female fireflies communicate by way of light signals they emit.

Many deep sea fishes possess the photophore organs, and this marine hatchetfish is one. Some residents of the aquatic depths generate light in order to orient themselves better in the darkness that reigns deep underwater. Others, however, use their glow to attract prey. A glance at the marine hatchetfish's head leaves little doubt that it is among them.

The photostomias, a member of the deep-sea family known as barbeled dragonfishes, can also light up. This creature that lives deep in the ocean has light organs situated behind its eyes that transmit a red glow - an unusual color among aquatic organisms. Many fellow ocean inhabitants cannot even perceive the light signals that the photostomias gives off.

Granted, mice normally don't light up. But that can all change once they're in a laboratory. Researchers can cause the animals to produce a fluorescent green protein in their cells. This type of protein normally appears in certain types of jellyfish. When placed under blue light, the entire mouse turns green - with the exception of its fur.

Theoretically, any animal could be induced to light up by manipulating its genes. A research institute in Uruguay, for example, is behind these lambs: They radiate yellow upon being exposed to ultraviolet rays. And a great variety of colors are possible: green, yellow, blue, cyan and red.