Jellyfish

A jellyfish’s graceful and often beautiful appearance, coupled with its rhythmical and languid swimming behavior, hide the danger that lurks among the deadly trailing tentacles.

The adult stages of jellyfish are known as medusae. They usually have umbrella- or helmet-shaped bodies, often referred to as the bell, although some species are square or box shaped. Jellyfish get their name due to the jellylike layer between the outer and inner layers of cells in their bodies. Much of this jelly is composed of water. When jellyfish are stranded on the beach, their jelly like nature is very easy to

see.

Under the Umbrella

The mouth is on the underside of the umbrella and leads up into the digestive cavity that spreads throughout the interior of the bell. There is no anus in jellyfish. There are many tentacles arranged around the edge of the umbrella, and these are armed with powerful stinging cells. They are used to catch prey and can be shortened or lengthened by the jellyfish at will. The edge of the umbrella is folded into a series of flaps. Between these flaps, and arranged rather like the position of the numbers 12, 3, 6, and 9 on a clock face, are sensory structures or balancing organs. Sometimes there are eight of these structures present, sometimes four, depending on the species.

Underneath the bell, and around the mouth, are four, often frilly oral arms, also equipped with stinging cells. They are called oral arms because they help get food into the jellyfish’s mouth when it feeds. In some species, the oral arms are used to look after developing larvae.