Cnidarians

No, sea anemone is Cnidaria

The stinging cell of a cnidarian contains a sac that houses a coiled up tube, immersed in venomous toxins. When triggered to fire by touch, chemical stimuli, and/or nerve excitation, a hinged lid opens, the tube rapidly shoots out of the sac by eversion (turning inside out), penetrates the skin of its victim, and introduces its venom along the entire length of the tubule. When large numbers of these stinging cells deliver a sufficient amount of venom, the prey (or predator) is paralyzed and can no longer cause damage to the fragile jellyfish.

The entire evagination process only takes a millisecond or two. These stinging cells are some of the most sophisticated in the entire animal kingdom. They fire only once and then are re-adsorbed, to be eventually replaced by a brand new stinging cell. New nematocyte stinging cells (containing the nematocyst sac organelle) are created near the base of a tentacle from interstital stem cells. They migrate down the tentacle while developing the complex internal nematocyst structure, and eventually distribute themselves into a species specific pattern along the tentacle.

No, they have no hard parts in their bodies.

Hydra will retract their tentacles into their body stem when touched. This is a response inherent in the plants from many centuries ago. Hydra do not like to be touched and close to protect themselves.

polyp

The medusa (jellyfish like) and the polyp (sea anenome like)

Organisms such as hydra are cnidarians, and all cnidarians belong to the taxonomic domain of Eukarya, members of which are characterised by having cells with nuclei. Eukarya covers all organisms in the Kingdom Animalia, as well as the Kingdoms Plantae, Fungi and Protista.

Cnidaria don't have gills or lungs, but they take in oxygen from surrounding water through diffusion.

1. digestion

2. circulation

3. physical support and movement

they produce asexually and sexually. The male and female produce sperm and eggs into the water. the sperm and eggs turn into larva after fertalization. the larva hooks onto rocks and dirt on the bottom of the ocean floor. It turns into a pupa and grows ridges. after time, the ridges break off and turn into medusae. then the stage begins all over again. look in the glencoe science book, grade six.

Hercules with the help of his nephew Iolau. However the fight may still be deemed fair as the Hydra had the aid of Cancer (the crab.)

Through a complex series of later events it is the venom of the Hydra that eventually kills Hercules.

The nematocysts allow the animal to hold the prey and venom is injected. The venom is often a neurotoxin that disables the prey and prevents too much damage to the soft bodied cnidarian. There are also chemicals injected that begin the digestion process. When the prey is ingested, more digestive chemicals are used.

Sponges and cnidarians commonly reproduce asexually by budding

By swimming using tentacles

There are four classes of cnidarians. Syphozoans, Hydrozoans, Cubozoans, and Anthozoans. Anthozoans don't have a medusa stage of life, so they don't get credit for being a jellyfish because they are never free swimming medusae. Syphozoans are considered by scientists to be a 'jellyfish', but the other two classes are considered jellies also (with reservations) because even though they have two layers of epithelial tissue with mesoglea (non-living gelatinous secretion) between the exodermal and the endodermal layers of 'skin', they are not radially symmetric. Other invertebrates of the gelatinous marine environment include the ctenophores and scalps.

Scyphozoans are characterized by their radially symmetric, umbrella shaped bodies.

Hydrozoans are characterized by their colony of polyps, which are not radially symmetric.

Cubozoans are characterized by their four sided, roughly cubical shaped bodies. They are also characterized by their 24 eyes, ability to perceive their environment, and actively both evade predators and pursue prey. These guys are not drifters, like most of the members of the 'jellyfish' distinction.

A Hydra is a mythological creature that has a simple shape. Try Google images. Hydras are said to be shaped much like a dinosaur body. They have four legs and a long stream lined tail, apparently used to help them swim. However, they are differential from Dinosaurs mainly because they have many heads. Most mythology states three separate heads, each with its own neck. Picture a Brontosaurus (the incredibly tall dinosaurs that are recognized by their long necks) but with separate necks attached to one body.

See related link below for a picture of a hydra.THIS is the main answer the body form of a hydra is called polyp.

there lifespan of 12 years but they could live up to 25 years

ctenophora are often found around piers. A good place to look would be the nearby sailboat marina if on the coasts. Are only marine (seawater). Not found in lakes, rivers, etc. If you see jellyfish ctenophores may be nearby

Hydra are carnivorous and will eat anything they can manage to catch including single celled animals, small crustaceans, worms, insects, and other tiny animals. They are also reported to eat small fish (fry) in the aquarium. Hydra use their tentacles for catching prey. The tentacles have special cells called nematocysts. To kill their prey, hydra shoot the nematocysts into the prey which paralyzes and kills it.

Apparently, the answer is yes. The Cantonese have a Seahorse Soup recipe that calls for four seahorses, pork stock, ginger and carrots. It is considered an added benefit to the meal if the male seahorses happen to be pregnant.

An opening

No. They are animals like jellyfish and coral.

Echinoderms generally have tube feet and are symmetrical radially. A feature they do not have is lungs to breathe air because they have a water based vascular system.

Digestion and absorption of food are major functions of gastrodermis .

Yes, they do. They use it to eat.