Cannonball Jellyfish

Pictured here is a cannonball jellyfish. Notice the brown coloring around the bottom of its bell.

Domain: Eukarya
Kingdom: Animalia
Phylum: Cnidaria
Class: Scyphozoa
Order: Rhizostomeae
Family: Stomolophidae
Genus: Stomolophus
Species: Stomolophus meleargis

For today’s species we’re going to head back to the phylum Cnidaria! Honestly, it’s one of my favorite phyla because it has coral, jellyfish, and siphonophores which are all really cool creatures to check out. So let’s go ahead and cannonball into today’s topic…

I’m trying too hard again, aren’t I?

Stomolophus meleagris, also known as the Cannonball Jellyfish, is aptly named because it is about the size and shape of a cannonball used to load cannons in the days of massive sea voyages, pirates, and colonization.

Though, compared to cannonballs, S. meleagris can be a lot prettier to look at. They range in color from white to brown and will have very neat looking markings of various colors around the bases of their dome heads. Unlike other jellyfish, cannonball jellies don’t have tentacles. Instead, they have short, forked oral arms that extend out and away from the dome a little.

Cannonball jellyfish are native in both the Atlantic and the Pacific oceans, found right off the coast and in estuaries. They’re most abundant in the waters off the southeastern United States and the Gulf of Mexico. S. meleagris populations span from New England to Brazil in the Atlantic Ocean, and from the Sea of Japan to the South China Sea in the Pacific.

In fact, they are considered a common menu item in Asian markets and are dried and processed right after capture. Humans aren’t the only species that eats these guys; the most important is the endangered leatherback turtle, which only eats S. meleagris.

The jellies themselves eat macrocrustaceans, certain fish larvae, and zooplankton; and they eat by sucking water in where several tiny “mouths” are located. Fun fact: their scientific name roughly translates to “many mouthed hunter”.

Like other cnidarians, these guys do have stinging cells, however they don’t pose much of a threat to people. The pain of their stings isn’t too great, and it will cause mild irritation though, if you get stung in the eye that is a whole other can of worms—so make sure you always wear protective eyewear when in the ocean!

I first saw these jellies in aquariums growing up, and I always thought they looked a little goofy. I love watching them move about their tanks, and I can watch them for hours—just ask my husband!

I’ve never seen these guys while diving or snorkeling, which is a little disappointing, but there’s always next time. I’ve also not come across them while playing in the ocean on beach days, though I have seen plenty of them wash up on the sand. In fact, during one of my internships, I watched a few of them get pulled into estuaries during high tide, and it looked like they were just rolling with the current like a runaway cannonball!

Sources and cool links:
https://animaldiversity.org/accounts/Stomolophus_meleagris/ (totally check this out, it has a lot of good information!)
https://sites.google.com/site/barrierislandecology2013/aquatic-fauna/cannonball-jellyfish (this one also has more links and things to check out at the end.)
https://animalsake.com/facts-about-cannonball-jellyfish

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