Anthoathecata, or the athecate hydroids, are an

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

hydrozoans Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) 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 spe ...

belonging to the

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

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, ...

. A profusion of alternate

scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

s exists for this long-known and heavily discussed group. It has also been called Gymnoblastea and (with or without an emended ending ''-ae''), Anthomedusa, Athecata, Hydromedusa, and Stylasterina. There are about 1,200

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

worldwide.Schuchert, P. (2014). Anthoathecata. Accessed through: Schuchert, P. (2014) World Hydrozoa database at http://www.marinespecies.org/hydrozoa/aphia.php?p=taxdetails&id=13551 on 2014-10-31 These hydrozoans always have a polyp stage. Their hydranths grow either solitary or in colonies. There is no firm perisarc around the polyp body. The

medusa In Greek mythology, Medusa (; ), also called Gorgo () or the Gorgon, was one of the three Gorgons. Medusa is generally described as a woman with living snakes in place of hair; her appearance was so hideous that anyone who looked upon her wa ...

e, or

jellyfish Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...

, are solitary animals, with tentacles arising from the bell margin, lacking

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, crustaceans, and gastropods, A similar structure is also found in '' Xenoturbella''. T ...

s but possessing radial canals. Their

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

s are on the manubrium ("handle").Bouillon, J.; Gravili, C.; Pagès, F.; Gili, J.-M.; Boero, F. (2006). An introduction to Hydrozoa. Mémoires du Muséum national d'Histoire naturelle, 194. Muséum national d'Histoire naturelle: Paris, France. . 591pp. + 1 cd-rom Except in

Eudendriidae Eudendriidae is a taxonomic family of hydroids (Hydrozoa). The family contains around 85 species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can pro ...

and Laingiidae, prey can be captured by discharging harpoon-like structures ( desmonemes) from chambers ( cnidae) in specialized cells (

nematocyst A cnidocyte (also known as a cnidoblast) is a type of cell containing a large secretory organelle called a ''cnidocyst'', that can deliver a sting to other organisms as a way to capture prey and defend against predators. A cnidocyte explosively ...

s) on the tentacles. In hydrozoans, these are nearly always adhesive and entrapping, rather than puncturing and venomous as in other jellies.

Systematics

The close relationship of the orders Anthoathecata and Leptomedusae has been long known, but formerly it was also believed that these two were close to the order Limnomedusae. However, their closest relatives are the highly advanced

Siphonophorae Siphonophorae (from Ancient Greek σίφων (siphōn), meaning "tube" and -φόρος (-phóros), meaning "bearing") is an order within Hydrozoa, a class of marine organisms within the phylum Cnidaria. According to the World Register of Marin ...

, whereas the Limnomedusae are a rather primitive group, and not very closely related to these three Leptolinae, and might instead belong to the subclass

Trachylinae Trachylinae (also Trachylina, Trachylinida, etc.) is a subclass of hydrozoans. It is placed at order rank in many older classifications, and limited to contain the Narcomedusae, Trachymedusae, the Actinulidae, then considered an independent o ...

. Some uncertainty existed regarding the taxonomy of the order Anthoathecata. The most simple scheme, used until recently by most authors since it was proposed in 1913, divided the order into a smaller suborder ( Filifera) and a second larger one ( Capitata), but several unusual Anthoathecatae did not fit into this arrangement, and a considerable number did so awkwardly. The Porpitidae, for example, are a highly aberrant group, and were at one time even considered a separate order "Chondrophora". However, they are currently considered to be derived from Zancleida. In the early 21st century, the well-known '' Hydra'' and its relatives – and most of the supposed filiferan infraorders Tubulariida and Moerisiida – were determined to be a very ancient lineage, recognized as suborder Aplanulata. Although not all Anthoathecatae have been firmly placed in the

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

, most are fairly certainly assigned at least to one of the major subdivisions. As a notable exception, a

prehistoric Prehistory, also called pre-literary history, is the period of human history between the first known use of stone tools by hominins million years ago and the beginning of recorded history with the invention of writing systems. The use o ...

family, the Heterastridiidae, is still highly disputed regarding its relationships to the extant taxa, as are a small number of very aberrant and/or little-known species such as the aptly named '' Saccohydra problematica''. The family Clathrozoellidae is placed with the Filifera here; in others it is placed in the Leptomedusae and sometimes even synonymized with their family Clathrozoidae. By contrast, the supposed filiferan genus ''Anthohydra'' is in fact the leptomedusan '' Eugymnanthea''; similarly, "'' Gammaria''" is also a leptomedusan and properly spelled '' Grammaria''. The supposed athecate family Monobrachiidae is apparently a close relative of the Olindiasidae, and belongs in the Limnomedusae. Halammohydridae and Otohydridae, sometimes placed here, appear to be trachyline hydrozoans of the order Actinulidae.

Infraorders and families

Basal and ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' Anthoathecata * Genus '' Bibrachium'' Stechow, 1919 * Genus ''" Microstoma"'' Lesson, 1830 (''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

; non'' G.Cuvier, 1816: preoccupied) * Genus '' Saccohydra'' Billiard, 1914 * †Family Heterastridiidae (

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

) Suborder Aplanulata Collins, Winkelman, Hadrys & Schierwater, 2005 * Family Acaulidae Fraser, 1924 (formerly in Tubulariida) * Family Boeromedusidae Bouillon, 1995 (formerly in Moerisiida) * Family Boreohydridae Westblad, 1947 (formerly in Tubulariida) * Family Myriothelidae Hincks, 1868 (including Candelabridae, Symplectaneidae; formerly in Tubulariida) * Family Corymorphidae Allman, 1872 (including Amalthaeidae, Branchiocerianthidae, Euphysidae, Hypolytidae , Monocaulidae, Paragotoeidae, Steenstrupiini, Trichorhizini; formerly in Tubulariida) * Family Hydridae Dana, 1846 (formerly in Moerisiida) * Family Margelopsidae Uchida, 1927 (including Pelagohydridae; formerly in Tubulariida) * Family Paracorynidae Picard, 1957 (formerly in Tubulariida) * Family Protohydridae Allman, 1888 (formerly in Moerisiida) * Family Tubulariidae Suborder Filifera Kühn, 1913 Basal or ''incertae sedis'' * Genus '' Brinckmannia'' Schuchert & Reiswig, 2006 * Genus '' Favonia'' Péron & Lesueur, 1810 (''

'') * Genus '' Kinetocodium'' Kramp, 1921 (Margelina: Hydractiniidae?) * Genus '' Lymnorea'' Péron & Lesueur, 1810 (= ''Limnorea; nomen dubium'') * Family Axoporidae Boschma, 1951 (

) * Family Bythotiaridae Maas, 1905 (including Calycopsidae; Pandeida?) * Family Clathrozoellidae Peña Cantero, Vervoort & Watson, 2003 (tentatively placed here) * Family Cordylophoridae von Lendenfeld, 1885 * Family Jeanbouilloniidae Pagès, Flood & Youngbluth, 2006 * Family Oceaniidae (Margelina?) * Family Tubiclavoididae Moura, Cunha & Schuchert, 2007 (Pandeida?) Infraorder Margelina Haeckel, 1879 (disputed) * Family Australomedusidae Russell, 1971 (including Platystomidae) * Family Balellidae Stechow, 1922 * Family

Bougainvilliidae Bougainvilliidae is a family of marine hydroids in the class Hydrozoa. Members of the family are found worldwide. There are sixteen accepted genera and about ninety-three species. Description Hydroids in this family can be solitary or colonial. ...

* Family Cytaeididae L.Agassiz, 1862 * Family Eucodoniidae Schuchert, 1996 * Family Hydractiniidae * Family Ptilocodiidae Coward, 1909 * Family Rathkeidae Russell, 1953 * Family Rhysiidae Hickson & Gravely, 1907; (tentatively placed here) * Family Stylasteridae (tentatively placed here) * Family Trichydridae Hincks, 1868 Infraorder Pandeida (disputed) * Family

* Family Magapiidae Schuchert & Bouillon, 2009 (formerly Laingiidae; tentatively placed here) * Family Niobiidae Petersen, 1979 * Family Pandeidae * Family Proboscidactylidae Hand & Hendrickson, 1950 * Family Protiaridae Haeckel, 1879 * Family Heterotentaculidae Schuchert, 2010 (formerly Russelliidae; tentatively placed here) Suborder Capitata Kühn, 1913 Basal or ''incertae sedis'' * Genus '' Cnidocodon'' Bouillon, 1978 (including ''Ramus'') * Genus '' Ctenaria'' (Zancleida: Zancleidae?) * Genus '' Oonautes'' Damas, 1937 (Zancleida: Zancleidae?) * Genus '' Paulinum'' Brinckmann-Voss & Arai, 1998 * Genus '' Plotocnide'' Wagner, 1885 (including ''Plankayon'') * Genus '' Propachycordyle'' Thiel, 1931 * Genus '' Pteronema'' Haeckel, 1879 * Genus '' Rhabdoon'' Keferstein & Ehlers, 1861 (including ''Pararhysomedusa'', ''Rhysomedusa'', ''Yakovia'') * Genus '' Tetraralphia'' Pagès & Bouillon, 1997 Infraorder Moerisiida Poche, 1914 (disputed) * Family Halimedusidae Arai & Brinckmann-Voss, 1980 (tentatively placed here) * Family Moerisiidae Poche, 1914 Infraorder Sphaerocorynida Petersen, 1990 (disputed) * Family Hydrocorynidae Rees, 1957 * Family Sphaerocorynidae Prévot, 1959 * Family Zancleopsidae Bouillon, 1978 Infraorder N.N.New name is required for the remaining Tubulariida, because Tubulariidae has been moved to Aplanulata. (disputed) * Family Cladonematidae * Family Corynidae * Family Euphysidae * Family Pennariidae McCrady, 1859 (including Halocordylidae) * Family Solanderiidae * Family Tricyclusidae Kramp, 1949 Infraorder Zancleida Russell, 1953 (disputed) * Family Asyncorynidae Kramp, 1949 * Family Cladocorynidae Allman, 1872 * Family Milleporidae Fleming, 1828 (= Milleporadae) * Family Porpitidae * Family Pseudosolanderiidae Bouillon & Gravier-Bonnet, 1988 * Family Rosalindidae Bouillon, 1985 * Family Teissieridae Bouillon, 1978 * Family Zancleidae Russell, 1953 (including Corynipteridae, Halocorynidae, Orthocorynidae)

References

Bibliography * Buecher, E., Goy, J. & Gibbons, M.J. 2005. Hydromedusae of the Agulhas Current. '' African Invertebrates'' 46: 27-6

External links

North East Atlantic TaxaFamily, genus and species list
{{Taxonbar, from1=Q14556976, from2=Q2344380 Hydroidolina Cnidarian orders