Jellyfish are radially symmetrical animals with a simple form, all with stinging capsules. Their radial symmetry allows them to respond to food or predators from any direction. ...
Jellyfish are radially symmetrical animals with a simple form, all with stinging capsules. Their radial symmetry allows them to respond to food or predators from any direction. ...
Sea Nettle Jelly (Photo: MJ Overy)
Jellyfish are members of the marine group phylum Cnidaria. These are radially symmetrical animals with a simple form, all with stinging capsules. Their radial symmetry allows them to respond to food or predators from any direction.
Purple-striped Jelly (Photo: MJ Overy)
Jellyfish do not have a brain. Instead, they have a basic nervous system. these consist of receptors which respond to light, odor and other stimuli and their response is a resulting combination of the feeds from these receptors.
Sea Nettle Jelly (Photo: MJ Overy)
Jellyfish have and outer layer, called the epidermis. This overs the external body surface. The inner layer is known as the gastrodermis. Between these two layers is another layer of thick jellylike substance called mesoglea .
They have a simple digestive cavity which behaves as a gullet, stomach and intestine. There is a single opening for both the mouth and anus. There are up to eight oral arms near the mouth. These are used to move food. The food is captured by tentacles.
Sea Nettle Jelly (Photo: MJ Overy)
Jellyfish possess a special breathing system. The walls of its body and tentacles are so fine that individual oxygen molecules are able to diffuse from the water into the internal organs. The same process enables carbon dioxide molecules to be removed from its body.
Purple-striped Jelly (Photo: MJ Overy)
A jellyfish moves by a combination of changing the size of the bell and by the use of ocean currents. The cosntration of the bell, by use of muscles, allows it some contril over vertical movement. Horisontal movement is largely dictated by ocean currents, tides, and wind.
Purple-striped Jelly (Photo: MJ Overy)
Numbers of jellyfish appear to be sensitive to the actions of man. One theory is the availability of the nutrients for plankton could be adversely affected by the increased use of fertilizers on the land. When fertilizers runoff into the ocean, they provide more food for the plankton. Larger supplies of plankton provide more food for the jellyfish, and this could explain the rapid increase of numbers. .
Purple-striped Jelly (Photo: MJ Overy)
Other human activities, including ocean pollution and dumping can significantly affect the numbers of jellyfish
Sea Nettle Jellyfish (Photo: MJ Overy)
Not all jellies sting, but this one certainly does!. When these long tentacles come into contact with prey, the stinging cells inject toxins and paralyze it . The prey is then moved to the location of the mouth-arms. Then the prey enters the mouth where it is digested.
Sea Nettle Jellyfish (Photo: MJ Overy)
When humans come into contact with the tentacles of certain jellyfish, they can experience intense pain and a burning sensation. This can last for hours. The effects can last for weeks through trhe appearance of red welts and itchy rashes. Swimmers should leave the water immediately, and seek immediate medical attention. The box jellyfish, which is found in the Indian Ocean and South Pacific, can sometimes cause a fatal reaction.
