Trepaxonemata: Difference between revisions

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{{Taxobox
⚫
#REDIRECT [[Rhabditophora]]
| name = Trepaxonemata
| image = Parasite170144-fig16 Spermatozoon ultrastructure in Digenea, Monopisthocotylea, Polyopisthocotylea.png
| image_caption = Spermatozoa of various Trepaxonemata (transverse sections, [[transmission electron microscopy]])
| regnum = [[Animal]]ia
| phylum = [[Platyhelminthes]]
| subclassis = '''Trepaxonemata'''
| subclassis_authority = Ehlers, 1985
| subdivision_ranks = Subgroups
| subdivision =
[[#Systematics|See text]].
}}
'''Trepaxonemata''' (from ''trepa''-, spiral + axoneme) is a subclass of the [[Platyhelminthes]] or [[flatworms]].<ref name="Ehlers1985">Ehlers, U. (1985). Das Phylogenetische System der Plathelminthes. Stuttgart: G. Fischer.</ref> It includes all [[parasite|parasitic]] flatworms (clade [[Neodermata]]) and several free-living species that were previously grouped in the now obsolete class [[Turbellaria]]. Therefore, it contains the majority of species in the [[phylum]] [[Platyhelminthes]], excluding the [[Catenulida]], and the [[Macrostomorpha]].


==Description==
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[[File:Axonemes 9+2 and 9+1 (Platyhelminthes) - with white background.png|thumb|left|Axoneme 9+2 (usual) and 9+“1” (Trepaxonemata)]]
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The Trepaxonemata are characterised by:
* biflagellate [[spermatozoa]]
* [[axoneme]] of the spermatozoa with a special type of dense core (9+“1” pattern).<ref name="Ehlers1986">{{cite journal|last1=Ehlers|first1=Ulrich|title=Comments on a phylogenetic system of the Platyhelminthes|journal=Hydrobiologia|volume=132|issue=1|year=1986|pages=1–12|issn=0018-8158|doi=10.1007/BF00046222}}</ref>
The [[axoneme]] in the spermatozoa of species of Trepaxonemata, also called "trepaxoneme" or "trepaxonematan axoneme" has nine peripheral doublets of [[microtubules]] as the usual 9+2 axoneme but the two central microtubules are replaced by a central core. This central core appears as a spiral when seen in longitudinal sections in [[transmission electron microscopy]].

This structure is found in all species of Trepaxonemata with very rare exceptions. The trepaxoneme is found only in the [[Platyhelminthes]]; no other [[phylum]] has this 9+“1” structure. However, the [[cilia]] in cells other than spermatozoa in species of Trepaxonemata have the classical 9+2 structure, for example in the [[Epidermis (zoology)|epidermis]] of in [[protonephridia]].

The Trepaxonemata is one of the rare examples of major groups in [[zoology]] named after characteristics of [[spermatozoa]], and especially after characteristics oberved with [[transmission electron microscopy]].

==Systematics==
Current classification of Trepaxonemata based on several morphological and molecular studies:<ref name=Egger>{{cite journal|last=Egger|first=B|author2=Lapraz, F. |author3=Tomiczek, B. |author4=Müller, S. |author5=Dessimoz, C. |author6=Girstmair, J. |author7=Škunca, N. |author8=Rawlinson, K. A. |author9=Cameron, C. B. |author10=Beli, E. |author11=Todaro, M. A. |author12=Gammoudi, M. |author13=Norẽna, C. |author14=Telford, M. |title=A transcriptomic-phylogenomic analysis of the evolutionary relationships of flatworms|journal=Current Biology|year=2015|volume=25|issue=10|pages=1347–1353|doi=10.1016/j.cub.2015.03.034 |pmid=25866392 |pmc=4446793}}</ref>

*Subclass [[Trepaxonemata]]
**Clade [[Amplimatricata]]
***Order [[Lecithoepitheliata]]
***Order [[Polycladida]]
**Clade [[Euneoophora]]
***Order [[Rhabdocoela]]
***Order [[Proseriata]]
***Clade [[Acentrosomata]]
****Clade [[Adiaphanida]]
*****Order [[Prolecithophora]]
*****Order [[Fecampiida]]
*****Order [[Tricladida]]
****Clade [[Bothrioneodermata]]
*****Order [[Bothrioplanida]]
*****Clade [[Neodermata]]
******Order [[Trematoda]]
******Order [[Monogenea]]
******Order [[Cestoda]]

== References ==
{{Reflist}}

⚫
[[Category:Rhabditophora| ]]

Revision as of 14:56, 2 March 2018

Trepaxonemata
Spermatozoa of various Trepaxonemata (transverse sections, transmission electron microscopy)
Scientific classification
Kingdom:
Animalia
Phylum:
Platyhelminthes
Subclass:
Trepaxonemata

Ehlers, 1985
Subgroups

See text.

Trepaxonemata (from trepa-, spiral + axoneme) is a subclass of the Platyhelminthes or flatworms.[1] It includes all parasitic flatworms (clade Neodermata) and several free-living species that were previously grouped in the now obsolete class Turbellaria. Therefore, it contains the majority of species in the phylum Platyhelminthes, excluding the Catenulida, and the Macrostomorpha.

Description

Axoneme 9+2 (usual) and 9+“1” (Trepaxonemata)

The Trepaxonemata are characterised by:

  • biflagellate spermatozoa
  • axoneme of the spermatozoa with a special type of dense core (9+“1” pattern).[2]

The axoneme in the spermatozoa of species of Trepaxonemata, also called "trepaxoneme" or "trepaxonematan axoneme" has nine peripheral doublets of microtubules as the usual 9+2 axoneme but the two central microtubules are replaced by a central core. This central core appears as a spiral when seen in longitudinal sections in transmission electron microscopy.

This structure is found in all species of Trepaxonemata with very rare exceptions. The trepaxoneme is found only in the Platyhelminthes; no other phylum has this 9+“1” structure. However, the cilia in cells other than spermatozoa in species of Trepaxonemata have the classical 9+2 structure, for example in the epidermis of in protonephridia.

The Trepaxonemata is one of the rare examples of major groups in zoology named after characteristics of spermatozoa, and especially after characteristics oberved with transmission electron microscopy.

Systematics

Current classification of Trepaxonemata based on several morphological and molecular studies:[3]

References

  1. ^ Ehlers, U. (1985). Das Phylogenetische System der Plathelminthes. Stuttgart: G. Fischer.
  2. ^ Ehlers, Ulrich (1986). "Comments on a phylogenetic system of the Platyhelminthes". Hydrobiologia. 132 (1): 1–12. doi:10.1007/BF00046222. ISSN 0018-8158.
  3. ^ Egger, B; Lapraz, F.; Tomiczek, B.; Müller, S.; Dessimoz, C.; Girstmair, J.; Škunca, N.; Rawlinson, K. A.; Cameron, C. B.; Beli, E.; Todaro, M. A.; Gammoudi, M.; Norẽna, C.; Telford, M. (2015). "A transcriptomic-phylogenomic analysis of the evolutionary relationships of flatworms". Current Biology. 25 (10): 1347–1353. doi:10.1016/j.cub.2015.03.034. PMC 4446793. PMID 25866392.
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