Mystic Aquarium

Info

Size:

A moon jelly can range in size from 2 to 15 inches in diameter.

Range/Distribution:

Moon jellies are found in coastal regions worldwide.

Appearance:

An adult moon jelly is commonly identified by the appearance of 4 horseshoe shaped reproductive organs which are visible through their clear bell.  The reproductive organs of the animal are located near the bottom of the stomach so when the jelly feeds the area around the gonads will take on the color of the prey.  Moon jellies have small tentacles lining the bell and distinctive oral arms, which assist in feeding, draping from the center of the bell.

Habitat:

Jellies are found in water with temperatures ranging from 48ْ -66ْ F (but can with stand water temperatures between 21ْ - 88ْ F).   These amazing invertebrates can even live in brackish water (a mixture of fresh and salt water); however, the bell will take on a flattened appearance when in areas of low salt concentrations.

Prey:

The moon jelly is a carnivorous animal which preys on small planktons such as larval crabs, shrimps and fish eggs.  Although movement is mostly dictated by the currents, a moon jelly can move into areas abundant with prey by pulsing their bell.  Although prey may be stung by the stinging cells (nematocysts) that line the tentacle, most become entangled in the mucous layer which covers the animal.  Food is then moved along eight canals which deposit food into the stomach.

Predators:

Moon jellies are preyed on by sea turtles, shore birds, fish species and other jelly species.

Mating Behaviors:

There are both male and female moon jellies.  The male will release a strand of sperm which the female will take internally through the mouth for fertilization.  The fertilized eggs undergo development in pockets in the arms that surround the mouth until they are ready to be released. Once released, the larvae spend a short period free-swimming before settling in one spot as a polyp.   The polyp will reproduce asexually by creating clones of it which will bud off the polyp and be released into the water column.  These released clones look like small plates with multiple arms and will mature and develop a complete bell after approximately 3 months.  Once mature, these jellies will reproduce sexually and the cycle will continue.

FAQ

Mystic Aquarium's jelly aquarist, Megan Priede, answers some questions about jellies.  Make sure to check out more of our interview with Megan under the video tab.

Q: Why have scientists changed the animals' name from jellyfish to jellies?

A: "Scientist are phasing out the term jellyfish and replace it with the more accurate term jellies or sea jellies.  Jellies do not possess fish characteristics; they don't have bones like a fish, scales like a fish, gills like a fish, etc.  Instead, jellies belong to the phylum cnidarai; this group of invertebrates (animals without backbones) share traits such as radial symmetry and stinging cells, just to name two.

Q: How many species of jellies are there in the world?

A: “There are currently 200 species of jellies identified but scientists believe that the number could be much larger as they are discovering new species of animals as they explore the ocean.”

Q: What do you call a group of jellies?

A: "A group of jellies is called a smack."

Q: Is it difficult to have house jellies at an aquarium?

A:  "Yes, jellies are delicate animals with almost 95% of their body being composed of water.  In an aquarium, staff must ensure that exhibits are built to best suit each species.  For instance, the upside down jelly lies with its bell resting on the botton of the exhibit and its tentacles waving in the water to collect plankton.  This species also needs sufficient light for the algae that it houses within its body to photosynthesize.  On the other hand, a moon jelly's exhibit will have customized systems to provide the appropriate flow for the animals to swim throughout the exhibit."

Q: How does the aquarium care for the jellies?

A: “Every morning a staff member will clean the exhibits of food and waste debris by carefully siphoning out waste without harming the jellies.  Temperatures and water quality are checked on all exhibits twice a day to make sure the water is clean and clear.  The aquarist will then feed all of the animals."

Q: How and what do you feed the jellies?

A: "Each jelly species may feed on a different type of prey.  The sea nettles will feed on small moon jellies while the moon jellies will feed on brine (sea monkeys).  Other jelly species may recieve a meal of fish eggs or shrimp.  The aquarist feeding the jellies will take care to ensure that all the animals receive the food they need."

Q: Are there any jellies listed on the endangered species list?

A: "There are currently no species of jellies listed on the IUCN red list."

Q: How do human activities influence the jelly population?

A: "Human activities can influence plant and animal life throughout the oceans.  A decrease in jelly population has not yet been documented, in fact, human activities seem to be increasing some populations of jellies.  Jellies play an important role in the food chain by feeding on fish and other zooplankton.  If the jelly population was to continue to increase it could lead to a chain reaction within the ocean food chain."

Photos

Videos

Podcast

Species of the Month Podcast: What if you get stung by a jelly?

Join Mystic Aquarium's Kelly Matis and MaryEllen Mateleska for a fun five minutes devoted to December's featured species: the moon jelly! In this podcast they tackle what to do when you get stung by a jelly at the beach?

Download

Kelly and MaryEllen want to hear from you! Send questions, comments and suggestions for future podcast topics to educationinfo@mysticaquarium.org.