The moon jellyfish are common in South Florida and live in temperate, coastal waters around the globe. They are comprised of 95% water, possessing no respiratory, excretory, or circulatory systems. They do, however, possess a fundamental nerve system connected to a nerve net that will respond to stimuli and creates the “pulsing” movement that jellyfish are known for.

Known predators of the jellyfish are sunfish, sea turtles, and even other jellyfish, such as the hydro-medusa. While there are predators, jellyfish are thriving and there are no real threats to their booming populations.

Jellyfish are masters of adaptation and thrive in low oxygen environments; they are strong bioindicators regarding the health and decline of our oceans. They are extremely weak swimmers, relying on ocean currents for locomotion. Their rudimentary swimming function serves only to keep them near the surface and to aid in feeding.

Moon jellyfish are carnivorous, feeding primarily on zooplankton and larval organisms. Their tentacles possess stinging cells called nematocysts and are used to stun and hold their prey, drawing their meal up to their gastrovascular cavity to be consumed. Jellyfish stings are common with recreational swimmers, often by simply bumping into the tentacles without realizing the animals are in the area. Jellyfish stings can be painful but, more often than not, are not a medical emergency.

In South Florida, you’re most likely to see moon jellies at the beach and offshore at the coral reef. This type of jellyfish has a translucent white, saucer-shaped bell with a blue-gray transparent disk at the center through which the horseshoe-shaped gonads are visible. Short, delicate, fringe-like tentacles hang from the bell margins. When deprived of food, they can shrink to one tenth of their original size to save energy; they redevelop to normal size when food is available. While they’re not poisonous, you’ll definitely know if you brush up against one because they’ll produce a sharp, uncomfortable stinging sensation. Moon jellies are found in Key West’s waters year round, however the seasons of late spring and summertime see them in the highest volume.

Yes, you can outsmart jellyfish. While they have a complex nerve system, they don’t actually have brains. They’re slaves to the ocean’s current and sea breeze, so if you see a jellyfish in the water, you can swim around it without fear of it following you. They’re not predatory by nature.

Jellyfish and coral are actually members of the same Phylum, Cnidaria. Many people think of coral as an inanimate rock in the water, but that couldn’t be farther from the truth—coral is a member of the Animal Kingdom. Jellyfish and coral share nematocyst stinging cells. That’s why if you brush up against coral, it also causes a sting, rash, cut or burn..

-source https://www.keywestaquarium.com/flori...