Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water and marine environments, including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites. Their distinguishing features are an uncentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living, jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Cnidarians are also some of the few animals that can reproduce both sexually and asexually.
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.
Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
Anthozoa is a class of marine invertebrates which includes sessile cnidarians such as the sea anemones, stony corals, soft corals and sea pens. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as planktons. 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.
Siphonophorae is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 species described thus far.
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mouth is fringed with tentacles. Although some species are solitary, most are colonial. The founding polyp settles and starts to secrete calcium carbonate to protect its soft body. Solitary corals can be as much as 25 cm (10 in) across but in colonial species the polyps are usually only a few millimetres in diameter. These polyps reproduce asexually by budding, but remain attached to each other, forming a multi-polyp colony of clones with a common skeleton, which may be up to several metres in diameter or height according to species.
The aggregating anemone, or clonal anemone, is the most abundant species of sea anemone found on rocky, tide swept shores along the Pacific coast of North America. This cnidarian hosts endosymbiotic algae called zooxanthellae that contribute substantially to primary productivity in the intertidal zone. The aggregating anemone has become a model organism for the study of temperate cnidarian-algal symbioses. They are most well known for the ability to clone themselves.
Carukia barnesi is an extremely venomous jellyfish found near Australia. Stings can result in Irukandji syndrome, and this species is commonly known as Irukandji jellyfish, although this name does not distinguish it from other Irukandji jellyfish such as Malo kingi.
Condylactis gigantea is a tropical species of ball anemone that is found in shallow reefs and other shallow inshore areas in the Caribbean Sea –more specifically the West Indies– and the western Atlantic Ocean including southern Florida through the Florida Keys. It is also commonly known as: giant Caribbean sea anemone, giant golden anemone, condylactis anemone, Haitian anemone, pink-tipped anemone, purple-tipped anemone, and Florida condy. This species can easily be seen growing in lagoons or in inner reefs as either individuals or loose groups, but never as colonies. They are often used as a model organism along with others in their genus for facultative symbiosis with monocellular algae.
Tubastraea, also known as sun coral or sun polyps, is a genus of coral in the phylum Cnidaria. It is a cup coral in the family Dendrophylliidae.
Millepora alcicornis, or sea ginger, is a species of colonial fire coral with a calcareous skeleton. It is found on shallow water coral reefs in the tropical west Atlantic Ocean. It shows a variety of different morphologies depending on its location. It feeds on plankton and derives part of its energy requirements from microalgae found within its tissues. It is an important member of the reef building community and subject to the same threats as other corals. It can cause painful stings to unwary divers.
Millepora platyphylla is a species of fire coral, a type of hydrocoral, in the family Milleporidae. It is also known by the common names blade fire coral and plate fire coral. It forms a calcium carbonate skeleton and has toxic, defensive polyps that sting. It obtains nutrients by consuming plankton and via symbiosis with photosynthetic algae. The species is found from the Red Sea and East Africa to northern Australia and French Polynesia. It plays an important role in reef-building in the Indo-Pacific region. Depending on its environment, it can have a variety of different forms and structures.
Dendronephthya hemprichi is a common soft coral found from Red Sea to Western Pacific.In may 2023 on the Mediterranean coast of Israel exactly on the coasts of the city of Sdot Yam many specimens were filmed, subsequently it was also photographed in Lebanon In Byblos.It is usually pink or orange with transparent trunk and it grows up to 70 cm. It exists at 30° N latitude. The smallest unit of this coral, like all other corals, is a polyp. This particular species of the Dendronephthya has the ability to reproduce sexually and asexually through broadcast spawning and clonal propagation, respectively.
The Enthemonae is a suborder of sea anemones in the order Actiniaria. It comprises those sea anemones with typical arrangement of mesenteries for actiniarians.
Millepora complanata, commonly known as blade fire coral, is a species of fire coral in the family Milleporidae. It is found in shallow waters in the Caribbean Sea where it is a common species. The International Union for Conservation of Nature has assessed its conservation status as being critically endangered.
Pennaria disticha, also known as the Christmas tree hydroid, is a species of athecate hydroid in the family Pennariidae. Colonies are common in the Mediterranean Sea growing on rocks close to the surface. This species has been used in research into prey capture.
Euphylliidae are known as a family of polyped stony corals under the order Scleractinia.
Hydra viridissima is a species of cnidarian which is commonly found in still or slow-moving freshwater in the Northern temperate zone. Hydra viridissima is commonly called green hydra due to its coloration, which is due to the symbiotic green algae Chlorella vulgaris which live within its body. These creatures are typically 10 mm long and have tentacles that are about half of their length. They are strictly carnivorous and typically feed on small crustaceans, insects and annelids. Hydra are normally sessile and live on aquatic vegetation. They secrete mucus to attach to substrate using their basal disc.
Physonectae is a suborder of siphonophores. In Japanese it is called 胞泳.
Zancleidae is a family of cnidarians belonging to the order Anthoathecata.
