Hydroids: Hydrozoa - Physical Characteristics, Behavior And Reproduction, Fire Coral (millepora Alcicornis): Species Accounts, No Common Name (distichopora Violacea): Species Accounts - GEOGRAPHIC RANGE, HABITAT, DIET, HYDROIDS AND PEOPLE, CONSERVATION ST
medusae plants sea fish
Hydroids live all over the world.
Hydroids live in all water habitats, from sea caves to deep-sea trenches, from lakes and ponds to rocky coasts and between grains of sand.
Hydroid polyps and medusae feed on almost all animals, from plankton, or microscopic plants and animals drifting in water, to fish.
The medusae of hydroids prey on the eggs and larvae of fish that people need for food. Some hydroids are used for scientific research. Others inhibit the functioning of power plants by clogging their pipes and reduce the speed of ships by attaching themselves to their hulls. Some medusae and polyp colonies inflict severe stings on humans.
Hydroids are not threatened or endangered.
Additional Topics
Hydroids (HIGH-droyds) have two body forms. One is the medusa (mi-DOO-suh), a jelly-like, umbrella-shaped, freely swimming form with a mouth and tentacles that face down. The other is a colony of polyps (PAH-luhps), or tube-shaped sacs that have a mouth and tentacles that face up. The polyp form is fixed to the material on which it lives. Most hydroids have both a medusa and a polyp stage. Medusae…
Some medusae remain immobile in the water, their tentacles outstretched, ambushing their prey. Others cruise across the water to catch their prey. Polyps simply extend their tentacles to catch passing prey. They also form currents by moving their tentacles to direct food particles toward their mouths. Polyps compete for space and defend their territory. Medusae are sharply individual but can be ga…
Physical characteristics: The polyps of fire coral colonies form massive, horn-shaped, upright branches. Large feeding polyps are surrounded by smaller catching-defending polyps. The feeding polyps are short and stout, with four to six short tentacles around the mouth. The catching-defending polyps are long, slender, and mouthless. The reproductive polyps are embedded in the surface of the coral. …
Physical characteristics: Distichopora violacea (abbreviated as D. violacea) lives as a polyp colony that looks like coral. It is purple with white tips. There are an equal number of catching-defending polyps on both sides of a row of irregularly shaped holes on the surface of the colony. Geographic range: D. violacea lives in the Indian and Pacific oceans and in the Red Sea. Specific distribution…
Physical characteristics: Aglantha digitale (abbrviated as A. digitale) is a medusa with a cylindrical umbrella that is about three-eighths of an inch to 1.5 inches (10 to 40 millimeters) high. The umbrella is about twice as tall as it is wide and has a small cone at the top. The mouth has four simple lips. Eight long, sausage-shaped sex glands hang freely inside the hydroid just under the top of …
Physical characteristics: The polyp colonies of Aequorea victoria (abbreviated as A. victoria) are small and unbranched and have creeping stems. The outer covering is thin and has a cap made of many flaps. The colony of A. victoria has twenty tentacles connected by a membrane at the base. The medusae of A. victoria are small when they leave the polyp colony, having only two tentacles and four cana…
Physical characteristics: A Portuguese man of war colony consists of a large, purplish blue gas-filled balloon that floats on the sea surface carrying the polyps. The balloon can reach a length of almost 12 inches (30 centimeters). A sail running lengthwise along the top of the balloon allows the man of war to move with the wind. The polyps form clusters at the mouth end of the balloon. Each clust…
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