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Zoanthids ( order Zoantharia, also called Zoanthidea or Zoanthiniaria) are an order of
cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...
ns commonly found in
coral reefs A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. ...
, the deep sea and many other marine environments around the world. These
animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
s come in a variety of different colonizing formations and in numerous different colors. They can be found as individual polyps, attached by a fleshy
stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...
or a mat that can be created from small pieces of
sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
, sand and rock. The term "zoanthid" refers to all animals within this order Zoantharia, and should not be confused with "'' Zoanthus''", which is one genus within Zoantharia. These are among the most commonly collected corals in reef aquaria, easily propagating and very durable in many water conditions.


Nomenclature controversy

The name of the order is controversial. Non-specialists often use the term Zoanthidea whereas most taxonomists use Zoantharia. The term Zoantharia in turn is used temporarily instead of Hexacorallia. However, major taxonomic papers published since 1899 by specialists (O. Carlgren and F. Pax have described more species than all other authors combined) use Zoantharia, and most recent specialists on the order continue to use the term Zoantharia.


Characteristics

Zoanthids can be distinguished from other colonial anthozoans and soft coral by their characteristic of incorporating sand and other small pieces of material into their tissue to help make their structure (except for the family Zoanthidae). A main characteristic of the order is that their tentacles are all marginal. Most species propagate asexually and the offspring of the original polyp remain connected to each other, by a
stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...
al network or coenosarc. Some species are solitary. While the most well-known zoanthids are the zooxanthellate genera found in tropical and sub-tropical waters (primarily ''Zoanthus'' and '' Palythoa''), many other species and genera exist, some still relatively unknown to science. Many zoanthids (in particular the genera Epizoanthus and Parazoanthus) are often found growing on other marine invertebrates. Often in zooxanthellate genera such as ''Zoanthus'' and ''Palythoa'' there are a large number of different morphs of the same or similar species. Such zooxanthellate genera derive a large portion of their energy requirements from symbiotic
dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...
s of the genus '' Symbiodinium'' (zooxanthellae), similar to many corals, anemones, and some other marine invertebrates.


Families and genera

The families and genera within the order Zoantharia (also known as Zoanthidea) are: * Abyssoanthidae ** ''
Abyssoanthus ''Abyssoanthus'' is a genus of cnidarian Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), includ ...
'' Reimer & Fujiwara in Reimer, Sinniger, Fujiwara, Hirano & Maruyama, 2007 Suborder Macrocnemina * Epizoanthidae ** '' Epizoanthus'' Gray, 1867 ** '' Paleozoanthus'' Carlgren, 1924 ** '' Thoracactis'' Gravier, 1918 * Hydrozoanthidae ** '' Hydrozoanthus'' Sinniger, Reimer & Pawlowski, 2010 ** '' Terrazoanthus'' Reimer & Fujii, 2010 * Microzoanthidae ** '' Microzoanthus'' Fujii & Reimer, 2011 * Nanozoanthidae ** '' Nanozoanthus'' Fujii & Reimer, 2013 * Parazoanthidae **'' Antipathozoanthus'' Sinniger, Reimer & Pawlowski, 2010 **'' Bergia'' Duchassaing & Michelotti, 1860 **'' Bullagummizoanthus'' Sinniger, Ocaña & Baco, 2013 **'' Corallizoanthus'' Reimer in Reimer Nonaka Sinniger & Iwase, 2008 **'' Hurlizoanthus'' Sinniger, Ocaña & Baco, 2013 **'' Isozoanthus'' Carlgren, 1905 **'' Kauluzoanthus'' Sinniger, Ocaña & Baco, 2013 **'' Kulamanamana'' Sinniger, Ocaña & Baco, 2013 **'' Mesozoanthus'' Sinniger & Haussermann, 2009 **'' Parazoanthus'' Haddon & Shackleton, 1891 **'' Savalia'' Nardo, 1814 (synonym: ''Gerardia'') **'' Umimayanthus'' Montenegro, Sinniger & Reimer, 2015 **'' Zibrowius'' Sinniger, Ocaña & Baco, 2013 Suborder
Brachycnemina Brachycnemina is a suborder of zoanthids in the order Zoantharia. Genetic analysis has been used to suggest Brachycnemina is a monophyletic group Genetic divergence, diverging within the paraphyletic Macrocnemina. Characteristics Brachycnemia sp ...
* Neozoanthidae ** '' Neozoanthus'' * Sphenopidae ** '' Palythoa'' Lamouroux, 1816 ** '' Sphenopus'' Steenstrup, 1856 * Zoanthidae ** '' Acrozoanthus'' Saville-Kent, 1893 ** '' Isaurus'' Gray, 1828 ** '' Zoanthus'' Cuvier, 1800 Note: there are some zoanthid genera such as '' Neozoanthus'' or '' Paleaozoanthus'' for which there are currently only few data available, those zoanthids having never been found again since their original description.


Aquaria

Zoanthidae include many species popular in the fishkeeping world, among hobbyists and professionals. They are relatively easy to keep alive and healthy, and will often spread to cover rocks in their bright circles of color. They are known by some as carpet coral, button polyps, and "zoas" or "zoos."


Captive propagation

Zooanthids and Palythoa are propagated in captivity by cutting the polyps apart using a scalpel or scissors then attaching to a surface with cyanoacrylate glue. Care must be taken when cutting zooanthids because, if the palytoxin gets in the bloodstream a person will become very ill. Drying the polyps with paper towel then gluing them to a small base with gelled cyanoacrylate glue ensures they do not drift in the aquarium when reintroduced.


Dangers

Some (but not all) members of this order contain the highly toxic substance palytoxin. Even in small quantities, Palytoxin can be fatal should it be ingested or enter the blood stream. If delivered immediately, it has been suggested that
vasodilator Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. Blood vessel wal ...
s can be injected into the ventricle of the heart to act as an
antidote An antidote is a substance that can counteract a form of poisoning. The term ultimately derives from the Greek term φάρμακον ἀντίδοτον ''(pharmakon antidoton)'', "(medicine) given as a remedy". An older term in English which is ...
. A 2010 study found toxic zoanthids in three Washington, D.C. area aquarium stores. Reports are varied and conflicting on the potential dangers of handling the animal in the aquarist hobby. General opinion and practical experience holds that in order for this toxin to be dangerous to humans, the average aquarist would need to ingest the zoanthid in sufficient quantities, or brush a recent cut over it, and average handling, propagation and aquarium maintenance is unlikely to pose any danger beyond a localized skin reaction. Other sources state that palytoxin can be absorbed through intact skin, and the danger of acute poisoning from venomous zoanthids is quite real. According to a report an aquarist was poisoned through skin injuries on fingers by a species of '' Parazoanthus'', but recovered after three days. His zoanthid was found to contain 2-3 milligrams of PTX per gram. Palytoxin has also been known to damage the eyes of aquarists who attempt to propagate the coral by cutting it and being squirted in the eye. Temporary blindness and permanent blindness have been reported. It is always recommended to wear proper eye protection when cutting corals. Research shows that in sublethal quantities, Palytoxin is a tumor promoter, and is being studied in relation to signaling pathways in skin cancer genesis. Generally it is considered proper practice to always wear appropriate protective gloves when reaching into salt water tanks and handling sea invertebrates..Nicholas Violand
"Aquarium Science: Palytoxin and You"
''Tropical Fish Hobbyist Magazine''


Diet

Zoanthids feed both by
photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
, aided by the zooxanthellae they contain, and by capturing
plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
and particulate matter. Although photosynthesis aids in their nutrition, even species that do not actively capture plankton cannot live through photosynthesis alone. Zoanthids can eat meaty foods, such as lancefish,
brine shrimp ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp or ''Sea-Monkeys, sea monkeys''. It is the only genus in the Family (biology), family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to t ...
,
krill Krill ''(Euphausiids)'' (: krill) are small and exclusively marine crustaceans of the order (biology), order Euphausiacea, found in all of the world's oceans. The name "krill" comes from the Norwegian language, Norwegian word ', meaning "small ...
, and bloodworms.


References


External links


Maintaining Zoanthids Tips, Care, Photos

Discussion About The Toxicity of Zoanthids

Gallery of Zoanthid Pictures

World's 2nd deadliest poison, in an aquarium store near you
{{Authority control Hexacorallia Anthozoan orders