Jellies also called jellyfish, are boneless, brainless and heartless, and are made almost entirely of water. They have been around since before the dinosaurs. When deprived of food they can shrink nearly 1/10th their size to save energy. They redevelop to normal size when food is available. Jellies are also related to coral and anemone.
Temperate and tropical oceans worldwide; near the surface of shallow bays and harbors
Plankton, small shrimp, fish eggs, and larvae.
Jellies eggs are fertilized when the female ingests floating sperm that were released by an adult male. When the female releases her fertilized eggs, they develop into a larval form which floats in the water until it finds a hard surface that it can anchor itself to. Once anchored it forms into a polyp (that resembles an anemone or an upside down jelly) and divides itself into a stacked series of saucer-like clones that then break off and swim away. As these forms called ephyra grow they form into adult jellies.
All seven species of Sea turtles include jellies in their diet. Other animals such as tuna, spiny dogfish, butterfish and ocean sunfish eat jellies as well.