Related Research Articles
Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelid, and cnidarians.
A polyp in zoology is one of two forms found in the Phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral end is attached to the substrate by means of a disc-like holdfast called a pedal disc, while in colonies of polyps it is connected to other polyps, either directly or indirectly. The oral end contains the mouth, and is surrounded by a circlet of tentacles.
A cnidocyte is an explosive cell containing one giant secretory organelle called a cnidocyst that can deliver a sting to other organisms. The presence of this cell defines the phylum Cnidaria. Cnidae are used to capture prey and as a defense against predators. A cnidocyte fires a structure that contains a toxin within the cnidocyst; this is responsible for the stings delivered by a cnidarian.
Vermes ("worms") is an obsolete taxon used by Carl Linnaeus and Jean-Baptiste Lamarck for non-arthropod invertebrate animals.
Ctenophora comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming, and they are the largest animals to swim with the help of cilia.
The coelom is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups.
Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new polyps from an original, founding individual. Colonies are strengthened by calcium carbonate and other materials and take various massive, plate-like, bushy or leafy forms.
In zoology, a tentacle is a flexible, mobile, elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work mainly like muscular hydrostats. Most forms of tentacles are used for grasping and feeding. Many are sensory organs, variously receptive to touch, vision, or to the smell or taste of particular foods or threats. Examples of such tentacles are the eyestalks of various kinds of snails. Some kinds of tentacles have both sensory and manipulatory functions.
Diploblasty is a condition of the blastula in which there are two primary germ layers: the ectoderm and endoderm.
Coelenterata is a term encompassing the animal phyla Cnidaria and Ctenophora. The name comes from Ancient Greek κοῖλος (koîlos) 'hollow', and ἔντερον (énteron) 'intestine', referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells, and radial symmetry. Some examples are corals, which are typically colonial, and hydrae, jellyfish, and sea anemones, which are solitary. Coelenterata lack a specialized circulatory system relying instead on diffusion across the tissue layers.
Medusozoa is a clade in the phylum Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa. Medusozoans are distinguished by having a medusa stage in their often complex life cycle, a medusa typically being an umbrella-shaped body with stinging tentacles around the edge. With the exception of some Hydrozoa, all are called jellyfish in their free-swimming medusa phase.
Mnemiopsis leidyi, the warty comb jelly or sea walnut, is a species of tentaculate ctenophore. It is native to western Atlantic coastal waters, but has become established as an invasive species in European and western Asian regions. Three species have been named in the genus Mnemiopsis, but they are now believed to be different ecological forms of a single species M. leidyi by most zoologists.
A zoophyte (animal-plant) is an organism thought to be intermediate between animals and plants, or an animal with plant-like attributes or appearance. In the 19th century they were reclassified as Radiata which included various taxa, a term superseded by Coelenterata referring more narrowly to the animal phyla Cnidaria and Ctenophora.
Although the phylogenetic classification of non-vertebrate animals remains a work-in-progress, the following taxonomy attempts to be useful by combining both traditional (old) and new (21st-century) paleozoological terminology.
Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton. As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. They make up most of the macroscopic life in the oceans.
Planulozoa is a proposed basal ParaHoxozoa clade, sometimes as sister of the Placozoa, but originally included Placozoa. In the latter case Planulozoa may be a senior synonym to Parahoxozoa. It contains the Cnidaria and the Bilateria. The Placozoa may be a sister of Cnidaria or more conventionally of Planulozoa. The clade excludes basal animals such as the Ctenophora, and Porifera (sponges).
Platyctenida is an order of comb jellies.
References
- 1 2 One or more of the preceding sentences incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Actinozoa". Encyclopædia Britannica . Vol. 1 (11th ed.). Cambridge University Press. p. 158.
