Types of Jellyfish

Cubozoa Jellyfish

• Cubozoans are commonly known as box jellies. These jellyfish have a square shape when seen from above. They have well-developed eyes and four evenly spaced tentacles or groups of tentacles. There are 20 known species of box jellies that live in tropical or semitropical waters.

  An Australian box jelly, the Chironex fleckeri, is extremely deadly and has caused human fatalities. It can grow to the size of a human head, has tentacles 9 feet long and can kill a human being in three minutes.

  Box jellies that live in Hawaii, the Carybdea alata and the Carybdea rastonii, give very painful stings and can cause anaphylactic shock. They plague Hawaii's leeward shores 10 days after the full moon.

  Box jellies also live off the coast of Florida and can weigh up to a pound. These jellyfish are rapid swimmers and although they do not kill human beings, they give very powerful stings.

Scyphozoa Jellyfish

• Most jellyfish you see on beaches belong to the class Scyphozoa. They are the only zoologically true jellyfish. They can range in size from less than a quarter-inch to more than 6 feet across. Cyanea arctica is the largest with tentacles over 120 feet long.

  The cannonball jellyfish, the Stomolophus meleagris, is also known as the cabbage head jellyfish. Appearing on beaches in large numbers, this bluish or yellowish jellyfish has venom which gives a mild sting. Shaped like a half-egg, it can be up to 7 inches in size.

  The moon jellyfish, Aurelia aurita, is a clear jellyfish about 7 inches in diameter which you can handle without feeling a sting. It also appears on beaches in large numbers.

  The sea nettle jellyfish, Chrysaora quinquecirrha, measures a foot in diameter and can give a bad sting. By-the-Wind sailor jellyfish, Velella velella, is another Scyphozoan and it lives in the waters off Cape Canaveral. It has a purple "raft" and a clear flexible sail which catches the wind and propels it like a sailboat.

  The lion's mane jellyfish, Cyanea capillat, is also known as the winter jelly because it is usually found in the winter. It has a bell shape and is 6 to 8 inches in size and is reddish-brown. Eight dense clusters of tentacles resemble a lion's mane.

Hydrozoans

• This third group is comprised of cnidarians that have a bell-shaped body and are commonly called jellyfish, yet they are technically hydrozoans. The Portuguese man-of-war belongs to this group.

  The man-of-war, Physalia physalis, has a body consisting of a gas-filled bladder-like float which can be blue or pink and up to a foot long. Half of the bladder is visible floating above the water. This crest acts as a sail. Beneath this are polyp clusters from which tentacles up to 165 feet in length hang.

  The sting is very harmful and painful to human beings and can cause fever, shock and problems with the heart and lungs.

  Comb jellies have transparent jelly-like bodies that are less than an inch long and have no tentacles. These jellies have bands made of combs or hairs that divide the comb jellies into eight areas. Sea walnuts are a species of comb jellies and swim in swarms. Pink comb jellies break apart when taken out of the water. Comb jellies do not sting and are often seen in Chesapeake Bay.