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Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular 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 worldwide.[1]
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 medusae, or jellyfish, are solitary animals, with tentacles arising from the bell margin, lacking statocysts but possessing radial canals. Their gonads are on the manubrium ("handle").[2]
Except in Eudendriidae and Laingiidae, prey can be captured by discharging harpoon-like structures (desmonemes) from chambers (cnidae) in specialized cells (nematocysts) on the tentacles. In hydrozoans, these are nearly always adhesive and entrapping, rather than puncturing and poisoned as in other jellys.[2]
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, 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.
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.[3] Although not all Anthoathecatae have been firmly placed in the phylogeny, most are fairly certainly assigned at least to one of the major subdivisions. As a notable exception, a prehistoric 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.
Bibliography
Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular 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 worldwide.
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 medusae, or jellyfish, are solitary animals, with tentacles arising from the bell margin, lacking statocysts but possessing radial canals. Their gonads are on the manubrium ("handle").
Except in Eudendriidae and Laingiidae, prey can be captured by discharging harpoon-like structures (desmonemes) from chambers (cnidae) in specialized cells (nematocysts) on the tentacles. In hydrozoans, these are nearly always adhesive and entrapping, rather than puncturing and poisoned as in other jellys.
Las antoatecadas (Anthoathecata) o antomedusas (Anthomedusae) son un orden de cnidarios de la clase Hydrozoa, aunque a veces se consideran un suborden del orden Hydroida. Su aspecto, filiforme y muy ramificado, recuerda al de algunos vegetales; no obstante, se trata de animales.
Se trata de formas coloniales que segregan una estructura ramificada común sobre la que se implantan. Existe una división funcional entre los individuos o zooides, que comprenden la colonia; algunos se dedican a funciones alimentarias, y son conocidos como gastrozoides o trofozoides; otros, son defensivos, los dactilozoides, erizados de cnidocitos; y otros, los activos reproductivamente, son los denominados gonozoides.
Los caracteres diagnósticos del grupo son dos:[7]
Su hábitat preferente es el marino; aunque hay géneros como Hydra que son propios de agua dulce. Algunas especies suelen disponerse en bordes rocosos a poca profundidad, bien batidos por el oleaje. Otras forman praderas,[7] y, en otras ocasiones, como muchos corales de la familia Stylasteridae, habitan en montañas marinas, a profundidades de hasta 5.000 metros.[8]
La distribución geográfica de los representantes del grupo incluye todos los océanos y latitudes, desde aguas polares a tropicales.[9]
Anthoathecata comprende las siguientes familias, agrupadas en tres subórdenes, y dos, o tres, géneros con especies existentes que conforman un grupo incertae sedis:[10]
Las antoatecadas (Anthoathecata) o antomedusas (Anthomedusae) son un orden de cnidarios de la clase Hydrozoa, aunque a veces se consideran un suborden del orden Hydroida. Su aspecto, filiforme y muy ramificado, recuerda al de algunos vegetales; no obstante, se trata de animales.
Les Anthoathecata constituent un ordre d'hydrozoaires.
Les hydrozoaires sont des membres de l'embranchement des cnidaires (les cnidaires sont des animaux relativement simples, spécifiques du milieu aquatique ; on y retrouve, entre autres, les coraux, les anémones de mer et les méduses).
Ces hydrozoaires ont tous un stade polype dans leur développement. Ils peuvent être solitaires ou coloniaux, et n'ont pas de périsarc ferme. Les méduses ne sont pas coloniales, n'ont pas de statocystes, mais des gonades ou un manubrium, des canaux radiaires et des tentacules rayonnant depuis la marge d'une coupe. Le cnidome inclut normalement des desmonemes (sauf chez les Eudendriidae et Laingiidae)[1].
Le nom de ce groupe prête à débat : selon les sources, ils sont orthographiés Anthoathecata, Anthoathecatae, ou Anthomedusae[1].
Selon World Register of Marine Species (13 juillet 2015)[1] :
Les Anthoathecata constituent un ordre d'hydrozoaires.
Les hydrozoaires sont des membres de l'embranchement des cnidaires (les cnidaires sont des animaux relativement simples, spécifiques du milieu aquatique ; on y retrouve, entre autres, les coraux, les anémones de mer et les méduses).
Anthoathecata Cornelius, 1992 è un ordine di Hydrozoa.[5]
All'ordine appartengono i seguenti quattro sottordini, uno dei quali indicato come incertae sedis:[5]
Anthoathecata Cornelius, 1992 è un ordine di Hydrozoa.
Anthoathecata is een orde van neteldieren uit de klasse van de Hydrozoa (hydroïdpoliepen).
Anthoathecata is een orde van neteldieren uit de klasse van de Hydrozoa (hydroïdpoliepen).
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