Moon jelly

Moon jellies are see-through jellyfish of the genus Aurelia. You can spot them by four horseshoe-shaped rings glowing through the top of the bell. They float in the Atlantic, Arctic, Pacific and Indian Oceans, and are especially common in temperate waters such as those off Japan, Korea, New Zealand and northern Europe.

Like other jellyfish, a moon jelly has no brain, heart or bones, and its body is about 95 percent water. Scientists have studied this group a lot, and DNA studies show there are more species than anyone guessed from looks alone. They drift in coastal and open ocean waters, and their pale bell is thin and almost clear. Most people who touch one feel little or no sting.

Stings and food

Moon jellies lack long, strong stinging tentacles. Instead hundreds of short, fine tentacles line the edge of the bell, and their sting is mild for most people. They drift and feed on tiny plankton, which they sweep toward their mouths. A bell usually measures 5 to 38 centimetres across. Their short tentacles also help move food to the mouth. Because the bell is so watery, a moon jelly is mostly a thin, floating cloud of jelly.

A life in two forms

Moon jellies change shape during life. The free-swimming adult jellyfish, either male or female, reproduces sexually. The baby stage, a tiny polyp stuck to the seafloor, makes new jellyfish without a partner. Because several species look nearly identical, they are hard to tell apart. Scientists have found that what looks like one species may actually be several, so careful DNA studies help sort them out.

On the globe

The model shows a translucent moon jelly with four rings visible on top of its bell.