Moon Jellyfish: Habitat & Reproduction

Instructor: Lauren Posey

Lauren has taught intermediate reading in an English Language Institute, and she has her Master's degree in Linguistics.

Moon jellyfish are one of the more common species of jellyfish. In this lesson you will learn about their habitat and distribution, as well as their reproductive cycle.

Moon Jellyfish

Have you ever gone walking along the beach and found a jellyfish washed up on shore? Or maybe you saw groups of them from a boat or dock, or even while swimming! If so, it's possible that what you saw were moon jellyfish. This is the common name for the species Aurelia arita, and they are one of the more common species of jellyfish. One way to identify them is their distinct four-loop pattern at the top of their bell. The bell is the top part of a jellyfish, above the tentacles. While jellyfish don't swim the way that fish do, they do use the bell to keep themselves near the surface.

The moon jellyfish has a distinctive four-loop pattern on its bell.
Moon jelly

Habitat

The moon jellyfish is extremely widespread. In fact, it can be found along almost all coastlines, other than the extreme poles, where it is too cold for them to survive. They are particularly common along coastlines in the Atlantic, Pacific, and Indian oceans. They are not common to the open or deep ocean, however. They stay near the surface and near the coast. They can also be found further inland, in estuaries or inland seas.

Moon jellyfish are typically seen in huge numbers. They are very common in warmer areas, such as tropical seas and coral reefs, but also in some cooler areas, such as along the European coast of the Atlantic Ocean. They are most common in salt water, but they can live in brackish, or mixed salt and fresh, water with very low levels of salt. Aurelia arita is a very common jellyfish found along a majority of the world's coastlines.

Reproduction

Moon jellyfish, similar to other species of jellyfish, can actually reproduce at two separate stages of life. One is the medusa, or adult, stage. The other is the polyp stage, where the jellyfish resembles a sea anemone.

Medusa Reproduction

One of the stages where a moon jellyfish can reproduce is the medusa stage. This is the stage most people think of when they think 'jellyfish.' It has the bell and tentacles, and drifts along the surface of the water. During this stage, the jellyfish can reproduce sexually. In fact, the four-loop pattern on the bell are the sexual organs. These are often pink colored in females.

Notice the pink color of the sexual organs.
Pink four loop pattern

Jellyfish typically release sperm and eggs into the water, where the eggs are fertilized, but in moon jellyfish, the female receives the sperm through the mouth and her eggs are fertilized internally. She incubates the eggs in arm pockets until they form into planula, or jellyfish larvae, and can be released into the water. The planula then attach themselves to reefs or rocks on the ocean floor. Once attached, they grow into polyps.

Polyp Reproduction

Though it is the most recognizable form, the medusa form is actually not how a jellyfish spends most of its life. A jellyfish might spend one year as a medusa, but it can spend several years in the polyp stage. Polyps are stationary and reproduce asexually.

The method of reproduction used by jellyfish polyps is known as budding, and it does look like a plant growing a new bud for a flower. The polyp essentially clones itself. The clone buds out of the original polyp and detaches to float freely in the water. These detached clones are known as ephyra. Once they are separated, ephyra develop into the adult medusa form.

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