Jellyfish are perhaps one of the most primitive invertebrates. They have no brain, no heart, no blood – only a simple nervous system that runs around its mouth. Its mouth is branching, and looks slightly like a coral. Jellyfish range from tiny Irukandji Jellyfish mere millimetres long to massive 2 metre long Fried Egg Jellyfish.
Perhaps the most commonly known Jellyfish is the Moon Jellyfish. It is a medium sized Jellyfish; roughly 30 cm around the perimeter. It is preyed on by the massive Fried Egg Jellyfish that I mentioned above.