Now that we're fully into summer and spending more time at the beach and in the water, we're likely to see more of the cannonball jellyfish (stomolophus meleagris, pictured above) washed up and stranded at the tideline. They're the most common jellyfish on our stretch of coastline, but fortunately also the least venomous; even so, it's best not to handle them, especially by the truncated tentacles below the bell, as they can still deliver a very mild sting.
Cannonballs appear offshore and in the mouths of estuaries starting in late spring and continuing into summer, abundant enough at times that commercial trawl fishermen consider them a nuisance for clogging and damaging nets. But some cultures, especially in Asia and the Pacific Rim, consider them a great delicacy served pickled or dried.
Among the most mysterious and beautiful of marine creatures, jellyfish of course aren't fish at all, but belong to a group of marine animals that includes corals and sea anemones. Their bells can be as small as an inch or so in diameter or more than a foot across. All jellyfish species are carnivorous and feed using their tentacles to carry prey - small organisms like plankton and krill, minnows, and even other jellyfish - to their mouths within the bell. They're in turn preyed upon by fish, turtles and other, larger jelly fish.
The most recognizable jellyfish to most people is the Portuguese Man O'War (Physalia physalis), highly venomous but only rarely seen in our waters, occasionally drifting inshore. Unlike other jellyfish, the Man O'War is actually a colony of many separate organisms. Tentacles may extend underwater up to sixty feet and inflict a very painful shock to muscles and joints that can require medical attention.
You're more likely to see, besides the cannonball, the Lions Mane (Cyanea capillata), although this variety usually only appears in colder weather, thus its alternate name of "winter jelly." Its tentacles can cause a mild burning sensation which usually dissipates in a few minutes.
Also common during warmer months is the Southern Moon Jelly (Aurelia marginalis), with its
transparent saucer-shaped bell and distinctive "horseshoe" shapes. Contact can produce a mild but temporary burning sensation.
Most important for treating jelly fish stings is removing any tentacles that remain attached to the skin. After that, recommended treatments, all with varied success, include sugar, vinegar and bicarbonate of soda. (Note that a common folk remedy, urine, can actually increase the intensity of the pain.) It's best to give these ethereal animals a wide berth. Learn more about them here.