What kinds of jellyfish do we have along our coast?

October 2006

Several species can be found in our waters, carried by currents, wind and tides. These hitchhikers are literally along for the ride.

Sea nettles usually arrive in our waters in August, when water temperatures are warmest.

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 appear.

Contrary to popular belief, 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, bones or brains to speak of. Some have long tentacles that dangle below their bells or flow gracefully behind as the animal is carried by currents. Others have short, stubby tentacles that barely reach below their bells.

Most jellies rely on their tentacles for catching food. The tentacles are covered with microscopic nematocysts, which contain barbs that act like harpoons. The barb’s sting paralyzes whatever it comes in contact with – plankton, shrimp, small fish or humans. The jelly’s oral arms then carry the food to its mouth.

Perhaps the most troublesome jelly that travels 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 jellyfish. It’s a colony of specialized polyps that live as one organism. The balloon-like float acts as a sail, pushing the colonythrough 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 to inshore waters. 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 in July 2005, some 75 people at Wrightsville and Carolina beaches were stung . A jellyfish sting health alert was issued and beaches flew red flags to alert beachgoers of dangerous surf 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.