Leptomedusae

Taxobox
name = Thecate hydroids

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image_width = 230px
image_caption = Crystal Jelly ("Aequorea victoria", Conica: Aequoreidae) with the parasitic amphipod "Hyperia medusarum" Photo by Sierra Blakely.
regnum = Animalia
subregnum = Eumetazoa
phylum = Cnidaria
subphylum = Medusozoa
classis = Hydrozoa
subclassis = Leptolinae
ordo = Leptomedusae
ordo_authority = Haeckel, 1879
subdivision_ranks = Suborders
subdivision =
Conica

Proboscidoidea
and see text
synonyms =Leptomedusa Haeckel, 1879
Leptothecata Cornelius, 1992
Leptothecatae Cornelius, 1992
Thecaphora Hincks, 1868
Thecaphorae Hincks, 1868
Thecata Fleming, 1828
Thecatae Fleming, 1828

Leptomedusae or Leptomedusa, commonly called thecate hydroids, are a cnidarian order in the subclass Leptolinae. They were formerly placed at suborder rank in the paraphyletic "Hydroida". Their closest living relatives, according to the modern view, are the Anthomedusae which are similar enough to have always been considered closely related, and the very apomorphic Siphonophora which were placed outside the "Hydroida" Given that there are no firm rules for synonymy for high-ranked taxa, alternate names like Leptothecata, Thecaphora or Thecata, with or without the ending emended to "-ae", are also often used for the Leptomedusae. [Schuchert (2005a)]

The about 1,900 species of Leptomedusae are characterized by a number of features: Their polyps are always living in colonies with the hydranths set in hydrotheca which are usually permanent and often long enough so the animal can fully retract into it; some have very reduced hydrothecae resembling Anthomedusae. There is a single whorl of tentacles.

The gonophores are borne on much reduced hydranths and usually protected in a peridermal gonotheca. Medusae forming on fully developed hydranths are extremely rare; usually the gonophores develop into medusae or into sessile sporosacs. The medusae have a shallow bell, bear the gonads on their radial canals, and usually have statocysts which are formed only from epidermal tissue and more than four tentacles and. The cnidome never has stenoteles.

Notable Leptomedusae include:
* Air fern ("Sertilaria argentea") of the Sertulariidae, sold dried as novelty "plants" and aquarium ornaments.
* Crystal Jelly ("Aequorea victoria") of the Aequoreidae, a bioluminescent hydrozoan.
* "Obelia" of the Campanulariidae

ystematics [Schuchert (2005b), MarineSpecies.org (2008)]

ORDER LEPTOMEDUSAE
* Basal and "incertae sedis"
** Family Eucopidae
* Suborder Conica
** A large number of uncertain affiliations
** Superfamily Campanulinoidea (disputed)
** Superfamily Plumularioidea
** Superfamily Sertularioidea
* Suborder Proboscidoidea
** Family Bonneviellidae
** Family Campanulariidae
** Family Phialuciidae

Footnotes

References

* (2008): [http://www.marinespecies.org/aphia.php?p=taxdetails&id=13552 Leptomedusae] . Retrieved 2008-JUL-08.
* (2005a): [http://www.ville-ge.ch/mhng/hydrozoa/hydrozoa-directory.htm The Hydrozoa Directory] - [http://www.ville-ge.ch/mhng/hydrozoa/intro/phylogeny.htm Hydrozoan Phylogeny and Classification] . Retrieved 2008-JUL-08.
* (2005b): [http://www.ville-ge.ch/mhng/hydrozoa/hydrozoa-directory.htm The Hydrozoa Directory] - [http://www.ville-ge.ch/mhng/hydrozoa/lepto/leptomedusae.htm Order Leptomedusae Haeckel, 1879] . Retrieved 2008-JUL-08.