The moon jellyfish (Aurelia aurita) are commonly seen in the Florida Keys 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 (Mola mola), sea turtles, and even other jellyfish, such as the hydromedusa (Aequorea victoria). While there are predators, jellyfish are thriving and there are no real threats to their booming populations.
Why their shape, size and movement matter
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.
Jellyfish in the Florida Keys
In the Florida Keys, there is one ocean creature likely to pose a threat that may not immediately occur to you, and that’s the jellyfish. These gelatinous creatures, many with orb-like bell bodies and stinging tentacles, have a sneaky way of ruining a day at the beach. The irony is they’re fascinating and oddly beautiful creatures, but if you see one in the water, do yourself a favor and steer clear. Read on for a few things to know about jellyfish in Key West and the Florida Keys.
The Most Common Types of Jellyfish
In Key West, 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.
The Portuguese man-o-war is what you really want to avoid. These bad boys are venomous, leaving extremely painful stings that in rare cases can be lethal. With a translucent, sail-shaped bell, man-o-wars float on the ocean’s surface, resembling a plastic bag. Their deep blue and purple tentacles trail beneath them up to six feet long. The good news is that if you’re alert, they’re easy to spot on the surface and avoid. The bad news is, those tentacles can sneak up on you when you least suspect them. If man-o-wars are known to be in the water, it’s a good idea to just stay out. They’re truly unpleasant creatures to come into contact with. Fortunately, we only see them in Key West during certain tides in the wintertime.
The comb jelly looks different from other jellies because it’s not made up of a bell and tentacles. Instead, it is a translucent walnut-shaped body with wart-like bumps. For this reason, it’s sometimes called a sea walnut. Comb jellies are translucent but refract light, appearing to have rainbow colors running down their bodies on the track of internal moving cilia. They can also make their own light (bioluminescence), flashing when disturbed.
The upside-down jelly does not look like the typical jelly, appearing as a flower on the seafloor. The bell is flat and shaped like a saucer. Color can vary, but is typically greenish to gray-blue. It has four pairs of elaborately branched but unfused oral arms. Instead of swimming, this jelly spends its life pulsing upside-down in shallow, sunlit water.
The cannonball jelly is a mostly harmless variety that sometimes washes up on beaches in large numbers. It is shaped like half an egg and may be up to 7 inches in diameter and either bluish or yellowish with a brown border. It is a good swimmer.
What are Sea Lice?
Related to the jellyfish, sea lice are actually microscopic larvae of jellyfish and other types of stinging organisms in the ocean. There are many varieties and, frustratingly, they’re basically impossible to see with the naked eye. In Key West, they often colonize on seaweed floating in the ocean, so try to avoid this while swimming. If you get hit by sea lice, it’s usually no more than a temporary mild itch or burning sensation that goes away as quickly as you feel it. On rare occasions, the sting of sea lice is delayed and can be rather painful and uncomfortable for days.
Jellyfish Don’t Have Brains
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 Are Related to Coral
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. As a rule of thumb, you should stay at least six feet away from coral while snorkeling to avoid coming into contact.
Jellyfish Feed on Zooplankton
While jellyfish aren’t exactly predatory, they are carnivorous. They feed on microscopic zooplankton, as well as fish eggs and even some juvenile fish.
Sea Turtles Feed on Jellyfish
How to Alleviate a Jellyfish Sting
In the unfortunate event that a jellyfish stings you, there are a few things you can do to relieve the sting. Most jellyfish stings can be treated by rinsing the area with salt water, applying vinegar or a baking soda paste and taking a pain reliever. However, should the sting be severe enough to require additional medical attention, follow these important tips and tricks.
Someone having a severe reaction to a jellyfish sting needs emergency care that may include:
- Cardiopulmonary resuscitation (CPR)
- An epinephrine injection, for anaphylactic shock
- Life support to stabilize breathing, heart rate and blood pressure
- Antivenin medication, if the sting is from a box jellyfish
- Pain medicine
Other circumstances also may require doctor-supervised treatment:
- A rash or other skin reaction due to delayed hypersensitivity may be treated with oral antihistamines or corticosteroids.
- A jellyfish sting occurring on or near an eye requires immediate medical care for pain control and a good eye flushing. You will likely be seen by a doctor specializing in eye care (an ophthalmologist).
The best treatment may depend on the type of jellyfish involved, but most stings can be treated with these simple home remedies:
- Remove stingers. Remove any pieces of jellyfish tentacle in your skin by rinsing the wound with seawater. You can also try gently scraping off the stingers with the edge of an ID card or a credit card. Avoid getting sand on and in the wound and do not rinse with fresh water or rub the area with a towel, as these actions may activate more stingers.
- Rinse with vinegar or apply a baking soda paste. Rinse the affected area with vinegar for about 30 seconds or apply a paste of baking soda and seawater. Each method may deactivate the stingers of some types of jellyfish.
- Take a hot shower or apply ice packs. Hot water, as hot as you can tolerate, but not above 113 F (45 C), and ice packs may help ease pain.
- Take a pain reliever and apply lotions. Apply calamine lotion or lidocaine to help relieve itching and discomfort.
- DO NOT URINATE ON JELLYFISH STINGS.