Cannonball Jellyfish (Stomolophus meleagris)

The Cannonball jellyfish, also known as the cabbage head jellyfish, is a mostly harmless (itís edible if you know how) 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. It may be bluish or yellowish with a brown border. It is a good swimmer.

Cannonball jellyfish swimming

The venom of the cannonball can give a mild sting, but generally, brushing against this jelly isn't enough to result in a sting. It goes without saying, that what would be a mild sting on the skin will be a very strong sting if the nematocysts get into your eyes.

The Cannonball Jellyfish is considered a delicacy in Japan, but it must be prepared properly, which usually means it is dried. However, you must understand that to be edible, it must be harvested while still alive and healthy. The ones washed up on the beach should not be eaten because once they are beached they decompose rapidly. Yuck!

Jellyfish salad in a Thai restaurant.

I ate this jellyfish salad in a Thai restaurant. It was really good. I don't know what type of jellyfish it was, but I do know that it was dried, then reconstituted with water before being seasoned and made into this delicious "salad."

Cannonball jellyfish in Destin, Florida.

S. Medrock sent in the photo above of his arm after he said bumped into a cannonball jelly, which left a dark brown gel on his arm. He said it was painful for about 6 hours. The next day it was very itchy and required hydrocortisone applications.

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Jellyfish and spider crab symbiotic relationship.

The Cannonball jellyfish often plays host to this type of Spider crab. It provides shelter and transportation for the crab, and presumably the crab shares the food that the jellyfish kills. Maybe the crab even takes a little nip of the jellyfish now and then.

I received a contribution of information from Dr. Richard Courtney with more info on the Cannonball jelly's ability to sting. Below are several quotes from Dr. Courtney's email:

"I'm a former instructor at the Naval Diving and Salvage Training Center in Panama City, FL. Taught the Dangerous Marine Life curriculum there, and for the FSU Scientist in the Sea Graduate Program. There is a huge bloom of cannonballs off the Panama City to Pensacola coast every year, thick. We surfed the jetties at the entrance to St. Andrew's Bay. Paddling through the jellies was no issue. The small tuft of tentacles sticking out of the "ball" never seemed to sting us. When surfing, the skeg [surfboard fin] would hit them staccato, bap, bap, bap........ there were that many in the water."

"So one afternoon a Navy pal decided to bean me with a cannonball jelly while I was surfing. The ball struck my arm, ruptured the jelly, and left a mildly stinging path across my arm and chest, no big deal. My buddy, laughing with glee at the impact, reached up to rub water from his eyes. Big mistake. He rubbed a few stray nematocysts into his eye from the jelly. Yow! That was the end of his surf day, red eyed and painful. It cleared up pretty quick, that day, no damage done. I was left with a little red itchy rash on my arm for about 2 days."

 "I think the relative mildness of the Cannonball Jelly sting is due to two main factors. First, the tentacles are short, largely encased in the jelly shroud, so contact is rare. Second, not all nematocyst are created equal. I suspect the stingers on the cannonball are small, poor penetration of thicker skin (but eyeballs, sclera and cornea, are quite delicate). Lastly, pure conjecture, but the venom may be rather impotent."

 "But make no mistake, a Cannonball Jelly can raise a welt, and bring a tear to your eye."

This is great information and I appreciate Dr. Courtney's addition to our knowledge of the Cannonball Jellyfish.

Cannonball jellyfish with blue coloration.

In the Pacific Ocean, the Cannonball jellyfish often takes on a deep blue color. This photo was taken in Puerto Penasco, Mexico. I've never seen a blue specimen in Florida. You can read more about the blue Cannonball jellyfish here.

Cannonball jellyfish on the beach.

This is how most people are likely to encounter the Cannonball jellyfish--decomposing on the beach.

More info: I read a Wikipedia entry about the Cannonball Jelly that says it does not generally sting. However, it does secret a toxin that is not only irritating to the skin, but MAY also cause irregular and dangerous heart rhythms. HOWEVER, the scientific study that the article references involves injecting the toxin directly into the bloodstream of rabbits and rats. The article's abstract does not say anything about effects on humans. So I would be very reluctant to conclude that merely coming into contact with a cannonball jellyfish could be harmful to the heart. I can find no specific reference (except in the Wikipedia article) that contact with a Cannonball (Cabbagehead) jellyfish is dangerous to humans. Here is a technical description of what the Cannonball jelly toxin can do to the heart of rabbits and rats.

Here is what Wikipedia says: "When disrupted the cannonball secretes a mucus out of its nematocyst that contains a toxin. The toxin harms small fish in the immediate area, and drives away most predators, except for certain types of crabs. Although cannonballs do not commonly sting humans, it still has toxins which can cause cardiac problems in animals and humans. The toxin causes irregular heart rhythms and problems in the myocardial conduction pathways. Such complications are associated also with toxins of other coelenterates. The toxin is also harmful to the eyes, when the nematocyst comes in contact with eyes it is very painful and is followed with redness and swelling."

Here's a link to the Wikipedia article:

Cabbagehead jellyfish swimming in Sebastian Inlet, Florida.

Copyright: David McRee,