Editor’s note: Due to the large numbers of jellyfish that have been seen in the ICW and near coastal waters lately (and the large number of questions we’ve been getting about those jellyfish), we’re reprinting this column about jellies that ran in 2018.
Dinosaurs roamed the earth a very long time ago. They first appeared around 250 million years ago and become extinct about 65 million years ago. But long before there were dinosaurs, jellyfish drifted in our world’s oceans. In fact, fossil evidence of jellyfish dates to over 500 million years ago.
Today, there are more than 2,000 known species of jellyfish, but scientists believe many more have yet to be discovered. Jellyfish may be very large — sometimes as large as us — or they may be very small. Most jellyfish live a year or less. Some only live a few days.
Despite their name, jellyfish aren’t really fish — they’re invertebrates, or animals without backbones. Although jellyfish mostly drift with the currents, they can spit water from their mouths to propel themselves forward.
Inside the bell-shaped body of a jellyfish is an opening or mouth. Jellyfish use this opening to eat, but also to discard waste. Tentacles hang from the body and contain tiny stinging cells. The stinging cells are used to paralyze prey before they’re eaten.
Even though jellyfish don’t attack humans, we sometimes accidentally run into them while swimming or wading. Jellyfish stings can be painful to humans and sometimes very dangerous. Although all jellyfish have stinging cells, the stings of some jellyfish are too weak for us to feel.
According to the Mayo Clinic, most jellyfish stings can be treated by carefully plucking visible tentacles with fine tweezers, and then soaking the skin in hot water. (Urine, on the other hand, does nothing.)
When we’re out on the water, we often see another jelly-looking animal that many folks call a jellyfish. But it’s not a jellyfish — in fact, it’s not even closely related to jellyfish. Comb jellies, also called sea walnuts, are little translucent oval blobs. Like jellyfish, comb jellies are gelatinous, but unlike jellyfish they don’t sting.
Eight rows of fine hairs called cilia (say “silly-uh”) run up and down a comb jelly’s body. These cilia, which resemble a hair comb, is how comb jellies got their name. The combs act like tiny oars, propelling the comb jelly through the water. The comb-rows often produce a rainbow effect. This occurs when light is scattered in different directions by the moving cilia.
Like jellyfish, comb jellies have existed on earth a very long time. In fact, very recently scientists learned that comb jellies are the oldest members of the animal kingdom. Previously this honor was bestowed upon sponges, but in 2017 genetic analysis revealed that comb jellies appeared first.
Betty Staugler is the UF/IFAS Extension Charlotte County agent for the Florida Sea Grant Program. She is active in many areas relating to boating, fishing, and watershed/coastal living. Sea Grant supports research and education activities that help Florida’s shoreline communities, industries and citizens wisely use the state’s coastal and marine resources. Contact her at firstname.lastname@example.org or 941-764-4346.