What are Cnidarians?
Cnidarians are a relatively simple phylum of animals (one among 38) which include the jellyfish, corals, sea pansies, sea pens, box jellies, and sea wasps. The phylum gets its name Cnidaria, from the Greek “cnidos,” meaning “stinging needle.” All cnidarians, including the stationary corals (the builders of the famous and beautiful coral reefs) have stinging cells called cnidocytes, which get their sting from organelles called nematocysts (also called cnidocytes or cnidoblasts). Cnidarians are thought to be among the most basal of all animals, excepting the sponges, and fossils dating to the Ediacaran period, 580 million years ago. Cnidarians left some of the first clearly identifiable animal fossils. There are over 10,000 species of cnidarian, divided into four main classes: Anthozoa (anemones, corals), Scyphozoa (true jellyfish), Cubozoa (box jellies) and Hydrozoa (Obelia, Aequorea, Portuguese Man o’ War, others.) Two additional minor groups include Polypodium (strange parasitic cnida
Today there are nine thousand species of cnidarians (phylum Cnidaria); the majority of them dwell in the sea. They admit sea anemones, hydras and jellyfish. Cnidarians catch food for their bodies using their armed tentacles which have stinging threads, called nematocysts. Animal skeletons Skeletons within animal’s works as a support model that maintains the shape of an animal allows animals to move around. Most skeletons found within animals are hard structures, either inside or off the animal’s body to which muscles are attached. Animal’s body, to which muscles are attached the skeleton usually protects the animals internet organs and, in the case of an insect’s external skeleton, which stops the animal from dying out. A skeleton found inside the body is called an endoskeleton. Hard outer skeleton that covers all or part of the body is called an exoskeleton. Hydrostatic skeleton is an internal skeleton found in soft-bodied animals like earthworms and its kind.About the Author: Uchenna
The name Cnidaria comes from the Greek word cnidos, for stinging nettle. All cnidarians have specialized cells that can inject poison into their prey or even hapless passers-by. With no hard parts, they are not preserved often, and their fossils may be difficult to recognize. The anthozoans include the sea anemones, sea pens, and true corals, which form large reefs today. The scyophozoans are the true jellyfish. Hydrozoans may look like true corals or true jellyfish, depending on the species and stage of their lifecycle. The cubozoans, which include the deadly box jelly, resemble true jellyfish but differ in some of their characteristics.First known fossil occurrence: Precambrian.Last known fossil occurrence: Quaternary. This group has living relatives.
