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Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, including jellyfish, hydroids, sea anemone, corals and some of the smallest marine parasites. Their distinguishing features are a decentralized 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.
The Portuguese man o' war, also known as the man-of-war, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or bluebottle, which is found mainly in the Pacific Ocean. The Portuguese man o' war is the only species in the genus Physalia, which in turn is the only genus in the family Physaliidae.
In biology, a colony is composed of two or more conspecific individuals living in close association with, or connected to, one another. This association is usually for mutual benefit such as stronger defense or the ability to attack bigger prey.
Hydrozoa is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.
Obelia is a genus of hydrozoans, a class of mainly marine and some freshwater animal species that have both polyp and medusa stages in their life cycle. Hydrozoa belongs to the phylum Cnidaria, which are aquatic organisms that are relatively simple in structure with a diameter around 1mm. There are currently 120 known species, with more to be discovered. These species are grouped into three broad categories: O. bidentata, O. dichotoma, and O. geniculata. O. longissima was later accepted as a legitimate species, but taxonomy regarding the entire genus is debated over.
Velella is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is Velella velella, a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raft, by-the-wind sailor, purple sail, little sail, or simply Velella.
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.
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.
Hydroidolina is a subclass of Hydrozoa and makes up 90% of the class. Controversy surrounds who the sister groups of Hydroidolina are, but research has shown that three orders remain consistent as direct relatives: Siphonophorae, Anthoathecata, and Leptothecata.
Leptothecata, or thecate hydroids, are an order of hydrozoans in the phylum Cnidaria. Their closest living relatives are the athecate hydroids, which are similar enough to have always been considered closely related, and the very apomorphic Siphonophorae, which were placed outside the "Hydroida". Given that there are no firm rules for synonymy for high-ranked taxa, alternative names like Leptomedusa, Thecaphora or Thecata, with or without the ending emended to "-ae", are also often used for Leptothecata.
Hydractinia symbiolongicarpus is one of the 30 + Hydractinia species known worldwide. This saltwater animal, from here on referred to as Hydractinia, is at the base of the Cnidaria phylum and in many ways, is similar to the freshwater Hydra. In the wild, Hydractinia feed on smaller invertebrates found in the shallow mud, however in laboratory environments they are fed brine shrimp. Hydractinia symbiolongicurpus and its sibling species, Hydractinia echinata, are the two species from the genus Hydractinia on which most work has been published.
Porpita porpita, or the blue button, is a marine organism consisting of a colony of hydroids found in the warmer, tropical and sub-tropical waters of the Pacific, Atlantic, and Indian oceans, as well as the Mediterranean Sea and eastern Arabian Sea. It was first identified by Carl Linnaeus in 1758, under the basionym Medusa porpita. In addition, it is one of the two genera under the suborder Chondrophora, which is a group of cnidarians that also includes Velella. The chondrophores are similar to the better-known siphonophores, which includes the Portuguese man o' war, or Physalia physalis. Although it is superficially similar to a jellyfish, each apparent individual is actually a colony of hydrozoan polyps. The taxonomic class, Hydrozoa, falls under the phylum Cnidaria, which includes anemones, corals, and jellyfish, which explains their similar appearances.
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.
Turritopsis nutricula is a small hydrozoan that once reaching adulthood, can transfer its cells back to childhood. This adaptive trait likely evolved in order to extend the life of the individual. Several different species of the genus Turritopsis were formerly classified as T. nutricula, including the "immortal jellyfish" which is now classified as T. dohrnii.
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.
Physonectae is a suborder of siphonophores. In Japanese it is called 胞泳.
Schuchertinia milleri, commonly known as the Miller hydractinia, hedgehog hydroid or snail fur, is a small colonial hydroid in the family Hydractiniidae, found in the eastern Pacific Ocean. It forms mat-like colonies on rocks, or sometimes on the mollusc shells occupied by hermit crabs.
Zancleidae is a family of cnidarians belonging to the order Anthoathecata.
Tima nigroannulata, commonly known as the elegant jellyfish, is a recently discovered colonial hydrozoa found on the Pacific coast of Japan.
References
- ↑ Christopher G. Morris; Academic Press (1992). Academic Press Dictionary of Science and Technology. Gulf Professional Publishing. pp. 945–. ISBN 978-0-12-200400-1.
- 1 2 Hughes, D.J. (1992). "Genotype-environment interactions and relative clonal fitness in a marine bryozoan". Journal of Animal Ecology. 61 (2): 291–306. doi:10.2307/5322. JSTOR 5322.
- 1 2 Sanders, Steven M.; Shcheglovitova, Mariya; Cartwright, Paulyn (2014-05-28). "Differential gene expression between functionally specialized polyps of the colonial hydrozoan Hydractinia symbiolongicarpus (Phylum Cnidaria)". BMC Genomics. 15 (1): 406. doi: 10.1186/1471-2164-15-406 . ISSN 1471-2164. PMC 4072882 . PMID 24884766.
- ↑ Terry, R.M. (1961). "Investigations of inner continental shelf waters off lower Chesapeake Bay. Part III. The phorozooid stage of the tunicateDoliolum nationalis". Chesapeake Science. 2 (1–2): 60–64. doi:10.2307/1350721. JSTOR 1350721.
- 1 2 Andrey N. Ostrovsky (16 December 2013). Evolution of Sexual Reproduction in Marine Invertebrates: Example of gymnolaemate bryozoans. Springer Science & Business Media. pp. 271–. ISBN 978-94-007-7146-8.
- ↑ Piraino, S (1991). "The adaptive pattern of growth and reproduction of the colonial hydroid Clavopsella michaeli". Coelenterate Biology: Recent Research on Cnidaria and Ctenophora. pp. 229–234. doi:10.1007/978-94-011-3240-4_32. ISBN 978-94-010-5428-7.
- ↑ Crow, James F. (1994). "Advantages of sexual reproduction". Developmental Genetics. 15 (3): 205–213. doi:10.1002/dvg.1020150303. ISSN 1520-6408. PMID 8062455.