Range: Tropical and temperate oceans worldwide Habitat: Open ocean and brackish waters Size: 1 foot (30.5cm) or wider Diet: Crustaceans, plankton, fish eggs, jellyfish, and more Threats: Sea turtles, marine birds, and fish Life span: Up to twenty-five as polyps; About one as medusae

Transcript:

Today on Animal Fact Files we’re discussing moon jellyfish. The name moon jellyfish is appropriate considering these cnidarians have been to space. They were sent to space as an experiment. Moon jellyfish have crystals in their bodies made of calcium sulfate which help them determine their orientation in the water based on gravity.

Humans have a similar crystal in their ears which helps us determine the tilt of our head as well as our forward motion. The question was: if a human baby is born in space, free from gravity, how would they react when experiencing gravity for the first time. The findings concluded that the moon jellyfish who were born in space and then traveled to Earth ended up developing identically to an earth-born moon jellyfish but the space-born jellies experienced vertigo which affected their motor skills. Potentially, this could mean that if humans ever intend to live outside of earth’s gravity field, then this could pose an obstacle we’ll have to face.

Keeping back to earth, moon jellyfish are sometimes called saucer jellyfish and they get their common names from their spherical appearance. They can be found in tropical and temperate oceans worldwide and tend to stay near the top of the water column. They will also drift into brackish water, or water consisting of both salt and freshwater. They have very little control over where they swim and sometimes wash up on beaches. Although they do sting, their stinging cells don’t penetrate human skin very well so they often leave little to no marks on our skin. Those with more sensitive skin, or thin skin, may be more affected.

Moon jellyfish can grow to be more than a foot (30.5cm) in diameter and are usually a semi translucent white color although their color can change based on what they eat. Crustaceans will turn them pink or purple while something like shrimp makes them more orange. They also eat plankton, fish eggs, and even other jellyfish. Food is gathered by mucus covered oral arms that hold the food in place while it is carried to the mouth.

There are about two dozen currently classified moon jellyfish species, but they can be difficult to tell apart from one another. The most stand out feature for the group as a whole are the four pronounced horseshoe shaped regions within their bell. These are where sperm or eggs are stored depending on the sex of the jellyfish.

Moon jellyfish have a pretty fascinating life cycle. When larvae from fertilized eggs hatch they will make their way to the ocean floor, find something to attach to and develop into polyps. The polyps will then produce clones of themselves that will detach from the polyp. These are called ephyrae and will end up growing into adult moon jellyfish which are called medusae. The polyps will do this for upwards of 25 years but medusae usually don’t live past their first. They’re eaten by sea turtles, sea birds, other jellyfish, and many fish species.

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