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 animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

ns commonly found in coral reefs, the deep sea and many other marine environments around the world. These

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

s come in a variety of different colonizing formations and in numerous different colors. They can be found as individual

polyps 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 (opposite to oral) end i ...

, attached by a fleshy stolon or a mat that can be created from small pieces of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

, 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 Hexacorallia is a class of Anthozoa comprising approximately 4,300 species of aquatic organisms formed of polyps, generally with 6-fold symmetry. It includes all of the stony corals, most of which are colonial and reef-forming, as well as al ...

. 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 stolonal network or

coenosarc In corals, the coenosarc is the living tissue overlying the stony skeletal material of the coral. It secretes the coenosteum, the layer of skeletal material lying between the corallites (the stony cups in which the polyps sit). The coensarc is comp ...

. 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 ''Palythoa'' is a genus of coral, anthozoans in the order Zoantharia.Reimer, J. (2018). Palythoa Lamouroux, 1816. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=205785 on 2018-08-27 D ...

''), 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 dinoflagellates of the genus ''

Symbiodinium : ''This is about the genus sometimes called Zoox. For the company, see Zoox (company)'' ''Symbiodinium'' is a genus of dinoflagellates that encompasses the largest and most prevalent group of endosymbiotic dinoflagellates known. These unicell ...

'' (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'' 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 ''Bergia'' is one of the two genera of plants composing the waterwort family, Elatinaceae. These are tropical to subtropical plants and sometimes aquatic in nature. Species include: *'' Bergia ammannioides'' *'' Bergia aquatica'' *'' Bergia au ...

'' 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 ''Parazoanthus'' is a genus of anemone-like anthozoans in the order Zoantharia Zoanthids (order Zoantharia also called Zoanthidea or Zoanthiniaria) are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine en ...

'' Haddon & Shackleton, 1891 **'' Savalia'' Nardo, 1814 (synonym: ''Gerardia'') **'' Umimayanthus'' Montenegro, Sinniger & Reimer, 2015 **'' Zibrowius'' Sinniger, Ocaña & Baco, 2013 Suborder Brachycnemina * Neozoanthidae ** '' Neozoanthus'' * Sphenopidae ** ''

'' 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 scalpal 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 zoanthids contain the highly toxic substance palytoxin. Palytoxin is one of the most toxic organic substances in the world, but there is an ongoing debate over the concentration of this toxin in these animals. However, even in small quantities, the

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

can be fatal should it be ingested or enter the blood stream. If delivered immediately, it has been suggested that vasodilators 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". Antidotes for anticoagulants are s ...

. 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 ''

'', 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 process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

, aided by the zooxanthellae they contain, and by capturing

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

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. It is the only genus in the family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to the first half of the 10th century AD from Urmia L ...

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish. Krill are consi ...

, 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
{{Taxonbar, from=Q1362080 Hexacorallia Cnidarian orders