"Jellyfish" is a misnomer. They are not fish at all, but the nomenclature has been around so long that it is accepted. Every so often, scientists and researchers try to use "Jellies" as an alternative term, but "Jellyfish" it remains. Jellyfish have been around for over hundreds and millions of years. They lived long before and long after the dinosaurs.
All jellyfish belongs to the phylum Cnidaria. The phylum term originated from Greek “cnidos”, which means "stinging nettle." "Cnidaria" also refers to the specialized cells, which contain the toxin, nematocysts. It is this stinging toxin that shocks prey and protects jellyfish from predators. This scientific name replaced the use of "Coelenterata," used to describe the radial and biradial symmetry.
History of the Jellyfish.
Scientists believe that all jellyfish came from a single ancestor. The Diploblasts were the first jellyfish known. It came about during the Metazoan radiation period.
Common Species of Cnidaria Phylum
Cannonball Jelly, Jellyball, Cabbage Head Jelly (Stomolophus meleagris)
This jelly has round bells with a brownish or reddish fringe. This group does not have tentacles. They have “oral” arms surrounding the mouth to form their feeding apparatus. The jelly is 8 – 10 inches in diameter. The worse damage that cannonballs cause is not by stinging humans, but clogging fishing nets.
Mushroom Jelly (Rhopilema verrilli)
They grow to 10 – 12 inches and are round bells. They do not have tentacles. They have long finger-like appendages that not quite tentacles or oral arms. Their toxin does not have an adverse affect on humans.
Lion's Mane, Winter Jelly (Cyanea capillat)
They earned the term, winter jelly because they live in the Artic oceans. It is typically bell shape. It ranges between 6 – 8 inches. It has reddish-brown oral arms along its side. The Lion's Mane became famous by Sir Arthur Conan's Sherlock Holmes, “The Adventure of the Lion's Mane.” In the novel, Lion's Mane could kill humans, but in real life, they have a moderate sting that causes a rash. If the recipient has an allergic reaction, the sting can be fatal. This is true of all jellyfish toxins.
Moon Jelly (Aurelia aurita)
This is a common species and a favorite of public aquariums. They are transparent with a saucer-shaped body. They have four pink half moon markings, which are their gonads. They range from 5 – 20 inches in diameter. Scientists believe that they are a group of subspecies rather than a species of their own. Their sting is uncomfortable to humans. They have a prickling sensation and mild burning.
The Newest Jellyfish
Big Red (Tiburonia granrojo)
Discovered, down 2100 feet in Monerey Submarine Canyon (in Mexico), in 2003, it floats in the deep ocean waters and a predator that devours its prey. Since 2003, many observed this species off the coast of California, Oregon and Washington. Scientists observed Big Red in Japanese waters and Hawaiian waters.
By the Wind Sailor, Purple Sail, Little Sail (Velella velella)
It floats on the surface of the ocean. They are tiny at almost 3 inches (7 cm). They are carnivores. They have toxic tentacles, which hang down from their body, to catch their prey. The toxin is harmless to humans.
These are just a few of the more than 2000 species of jellyfish that sail the seas today. Many more are yet to be discovered.