Moon jelly’s upper body can reach up to 12 inches in width
The aurelia aurita, more commonly known as the moon jelly, has enchanted humanity for generations.
With no brain, heart, eyes or ears, they float along the oceans’ currents carefree and majestic. Their lives begin around summertime when an adult male’s sperm floats through the ocean until it meets an adult female. Her fertilized eggs then begin to develop in pockets in her arms. During autumn, the eggs are released as free-swimming larvae known as planulae, which float in the water until they find a hard surface to anchor onto.
From there, they morph into a polyp, a small anemone-looking structure. The polyp uses asexual reproduction to release dozens of tiny immature jellyfish known as ephyrae. The ephyrae resemble snowflakes and will remain in this immature stage for around three months. Within this time, the ephyrae mature into the moon jelly’s final stage, the medusa.
Although they are still not fully grown, they are more recognizable after developing some of their adult characteristics. But they have not yet developed their four gonads situated at the bottom of the stomach.
Resembling a loosely arranged four leaf clover the gonads are the moon jelly’s reproductive organs and their most distinguishing feature.
Once fully grown, the moon jelly lives around six months to a year, and their bell-shaped upper body can reach up to 12 inches in width.
Like all of the moon jelly’s stages, the medusa relies primarily on the ocean currents for locomotion. However, they do have muscle cells in their upper body called coronal muscles.
They can contract these muscles and achieve movement this way, not to get from place to place but to keep themselves near the surface of the water.
The water’s surface has the highest concentration of plankton, a source of food for the moon jelly. Stinging cells known as nematocysts that line their tentacles are used in some cases as self-defense, but primarily to kill passing prey.
Dead or alive, the moon jelly’s prey becomes entangled in the mucous layer that covers them before being moved along eight canals that deposit food into the stomach and then get broken down by digestive enzymes.
Staying at the surface also can be a greater risk for the moon jelly. If they get too close to the surface, some shore birds will snatch them for food. Other predators include larger fish, sea turtles and humans.
In some areas, jellyfish are caught for food, or sometimes, jellyfish populations will be lowered simply to put tourists at ease. The moon jelly’s thin body leaves it easily affected by water pollution and more susceptible to being washed ashore where they cannot survive.
Despite its many obstacles and delicate appearance the moon jelly is a resilient animal. It can be found in oceans all around the world from warm to cool water temperatures. Although it is unknown how long the moon jelly has been around, jellyfish in general have been evolving and surviving for millions of years.
It would truly be a tragedy if the world lost these marvelous creatures. But with everyone’s help, the moon jelly can continue fostering wonder in people of all ages for years to come.
* Jessica Smith is a senior at Harmony School in Bloomington, Ind. She’s interning with the Maui Ocean Center as part of her senior project.