What kinds of jellyfish do we have along our coast?
October 16, 2006
Several jellyfish species can be found in our waters. Carried by currents, wind and tides, jellies are literally along for the ride.
During summer, moon jellies, sea nettles, cabbageheads and mushroom jellies are frequent visitors to our area. In fall, the lion’s mane and Portuguese man-of-war show up.
Surprisingly, not all jellies are harmful to humans, but unless you are knowledgeable about these aquatic ballerinas, it’s best to avoid contact, even if you find one washed ashore.
Jellies’ stinging cells, called nematocysts, can remain active even after the animal dies.
It’s interesting to note that jellies are about 95 percent water. They have no heart, no bones and no brains to speak of. Some have long tentacles that dangle below their bells, or flow gracefully behind as the animal is carried by the current. Others have short, stubby tentacles that barely reach below their bells.
Sea nettles usually arrive in our waters in August, when water temperatures are warmest.
Most jellies rely on their tentacles for catching food. The tentacles are covered with the microscopic nematocysts, which contain a barb that acts like a harpoon. The barb’s sting paralyzes whatever it comes in contact with – plankton, shrimp or small fish. The jellie’s oral arms then carry the food to its mouth. Jellyfish do not set out to sting humans. An encounter with a jellie is merely a case of happenstance.
Perhaps the most troublesome jelly traveling through our waters is the Portuguese man-of-war. Distinguished by its colorful pinkish-purple, balloon-like float, the man-of-war is not a true jelly. It’s a colony of specialized polyps that live as one organism. The balloon-like float acts as a sail, pushing the colony along through the ocean. Strong east or southeast winds can blow this sailor inshore during summer or early fall, and occasional winter or spring storms may also bring it ashore. The tentacles that stretch beneath the float can produce an extremely painful sting. The tentacles, or previously ejected nematocysts, can sting even after they become detached from the animal. This is also true of other jellyfish.
Another problem jelly is the sea nettle. In a four-day period last July, some 75 people at Wrightsville and Carolina beaches were stung . A jellyfish sting health alert was issued and beaches flew red flags to alert beach-goers of dangerous swimming conditions.
Everyone’s level of sensitivity to jellyfish toxin is different. Stings from some jellies may require a doctor’s care, especially for people with a history of allergies to bee stings.
To avoid jellyfish encounters, monitor the beach and the water, talk with lifeguards, and keep an eye out for jellies washed ashore. Beached jellies may be a sign to wait for another day to go for a swim.