Did you know?

Moon jellyfish have a secret weapon against predators! While their stings are mild to humans, they can be potent enough to paralyze and capture the tiny zooplankton they prey upon.

Key Characteristics of the Moon Jellyfish

Length: Up to 12 inches (30 cm)

Weight: Usually just a few ounces

Lifespan: A few months to a year

Diet: Zooplankton, small fish eggs, larvae, and other microscopic organisms

Conservation Status: Least concern

Habitat: Coastal and open oceans

This jellyfish is almost entirely translucent and can be recognized by its four horseshoe-shaped gonads

Published by Hamna Faizan

Marine Life Researcher and Lecturer, with an MSc in Zoology

Aurelia aurita, commonly known as Moon Jellyfish, includes about 25 species that like to stay in relatively warm waters. For practical purposes, they are all quite similar, if not identical; however, the genetic analysis points out clear differentiation.

Although the Moon Jellyfish can be located all over the epipelagic area, its distribution is most typically observed close to shore and in upwelling sites, where its food is more abundant. As a result of violent storms or surges that push them ashore, this animal isn’t a particularly great swimmer and is frequently discovered on coastlines.



Appearance

Their bell is clear or opaque, with one permeable circle in the middle that is typically blue. They can be identified by their distinct quadruple clover-shaped gonads, visible through the top of the dome, and typically range between 10 and 16 inches in diameter.

The moon jelly differs from many jellyfish in lacking long, potent stinging tentacles. Instead, they have hundreds of short, fine tentacles that line the bell margin. The moon jelly’s sting is mild and most people have only a slight reaction to it if anything at all.

The tendrils are packed in particular irritating cells known as Cnidocytes, like other genuine jellies. The reason why they have the name “Moon” is because of their rounded, shining crown or bell and tiny appendages. Its overall anatomy makes the jellyfish more of a floater than a swimmer, which is notoriously difficult for them.

Beneath the bell, four thicker, frilly oral arms extend outwards. They aid in moving food towards the mouth.

Did you know…

A distinctive feature is the four horseshoe-shaped gonads (reproductive organs) that often exhibit pink, purple, or orange coloration. Some populations have been observed to have biofluorescence, emitting a blue-green glow under certain light conditions.

This jellyfish is almost entirely translucent and can be recognized by its four horseshoe-shaped gonads
This jellyfish is almost entirely translucent and can be recognized by its four horseshoe-shaped gonads


Habitat

This jellyfish can be found in oceans where the temperature is between 43–88 °F; they typically are located in Greenland, the north-east Atlantic, the east coast of the US, and Canada, as well as in the Caspian. It’s not uncommon to find many Moon Jellyfish either washed up or near the shoreline. 

A large number of these jellyfish are called a “Bloom,” and it’s generally a sign that the surrounding area is negatively affected by human activity, resulting in either a reduction of predators or an upsurge in the available prey supply. Either way, they are a fairly resilient species that is able to survive in water conditions most sea species would perish in.

It is capable of only limited motion, and drifts with the current, even when swimming.
It is capable of only limited motion, and drifts with the current, even when swimming.


Diet

Moon Jellyfish feed on small life forms such as platyzoa, and plankton as well as larger forms like crustaceans and mollusks alongside fish eggs. The mechanism by which they acquire food is quite efficient, considering that their underwater mobility is practically non-existent, as they solely depend on favorable currents to push them in the favorable direction.

The tentacles are laced with cnidocytes mixed in the mucosal lining, which work by exploding small particles on the prey’s surface, resulting in paralysis and rendering the prey immobile and helpless.


Reproduction

Moon jellyfish have two main stages to their lifecycle: polyp and medusa. The latter is the adult, bell-shaped, floating jellyfish we are familiar with. The former is a small stalk that attaches to a rock and divides into buds that break free to become adults.

Aurelia jellyfish naturally die after living and reproducing for several months.
Aurelia jellyfish naturally die after living and reproducing for several months.

Adults reproduce by external fertilization, in which the male discharges sperm further into surrounding water and the female discharges eggs. After fertilization, the egg develops into a larva that spends considerable time in the pelagic habitat. The larva looks for a suitable location in the intertidal zone as it develops and ultimately adheres to the ocean floor, where it develops into a polyp. 

Each organism forms multiple clones of itself while it goes through the polyp phase that asexually reproduces and swims away before developing into a fully developed Moon Jellyfish. Most astoundingly, they can reverse their life cycles so that they age backward, rendering them to practically live forever.


Threats

In addition to the leatherback sea turtles and the ocean sunfish, Moon Jellyfish are also reported to be consumed by a range of shorebirds that might be more attracted to the krill and other smaller arthropods.

These jellyfish are more vulnerable to fungal and other disease issues in the environment due to the heated water at the summer’s end, where rapid daily mating and decreased natural food concentrations make tissue repair almost impossible. As a result, the majority of specimens are expected to perish.

The moon jelly differs from many jellyfish in that they lack long, potent stinging tentacles.
The moon jelly differs from many jellyfish in that they lack long, potent stinging tentacles.


6 More Facts about the Moon Jellyfish

  1. They have the ability of bioluminescence.
  2. This jellyfish has been around as early as 500 million years ago.
  3. Moon Jellyfish were passengers in the Space Shuttle Columbia mission in 1991.
  4. They are passive swimmers, largely at the mercy of currents and tides.
  5. They have a relatively short lifespan of around one year.
  6. Moon jellyfish populations can reflect ocean health, as they are sensitive to environmental changes


FAQs

How poisonous are Moon Jellyfish?

The Moon Jellyfish is distinct from numerous other jellyfish because it lacks lengthy, highly effective stinging appendages. Instead, the bell border is lined with thousands of tiny, delicate tentacles. The Moon Jellyfish has a faint sensation, and also most individuals only experience minor irritation or none at all.

What happens if you get stung by a Moon Jellyfish?

If you are stung by a Moon Jellyfish, don’t be alarmed; it won’t hurt you much. Essentially, Moon Jellyfish don’t possess a sting with enough intensity to pierce flesh. Rather, they will only provide a slight tingling feeling. You might experience modest discomfort and irritability, but these feelings should pass quickly.

How long can Moon Jellyfish live out of water?

Moon Jellyfish are known to live in water with very little oxygen content in some polluted waters, and they are paradoxically as resilient as they are fragile. However, outside of water, they can live for less than an hour, and depending on how strong the sun exposure is, the time just gets less and less.

How long do Moon Jellyfish live?

A polyp Moon Jellyfish can live up to a quarter of a century before becoming a mature Moon Jelly, whereas an adult Moon Jellyfish only lives a year and a half in tank confinement. Even if they are completely safe from predators, the procreation renders their immune system too weak to counteract any bacteria resulting in death.

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