Ctenophora

The cténophores ( Ctenophora , of the Greek ktenos , “comb”) or “cténaires” are marine organizations represented by approximately 100 species. Their name comes from the structure out of comb of lines of lash S locomotors. Their surface resemblance to the Méduse S formerly made them classify near these last in the group of the Coelentéré S, now fallen in Désuétude. They are predatory organizations Plancton ic.

Morphology

The cténophores have an ovoid, ribboned form or out of bell. They have a gelatinous, translucent aspect. They have the characteristic to be bioluminescent, detected relatively early because they are visible easily. They are extremely fragile thus very difficult to take. They are Diploblastique S but have a mésenchymateuse layer near to one 3rd layer. They have a symmetry biradiaire, have 8 lines of lashes forming of the combs, carry 2 large tentacles, for the locomotion and the other to capture the preys. The tentacles consist of colloblastes single, sticking cells which trap the small preys by a mucus. They are monomorphes: never of fixed stage.

Biology and ecology

They have a typical Larve called Cydippide. It is a group still rather badly known which poses a problem in the phylogenetic Classification because we have only very few data and certain genes have a slow rate of evolution compared with the bilatériens.

Reproduction

Except for some species about Platyctenida, the reproduction is sexuée. Almost all are Hermaphrodite S. the gonades are generally located in the vicinity of the lines of lashes and, with maturity, the sexual products are emitted in the sea by small named openings “gonopores”. The release of the emission of the Gamète S is stimulated by certain luminous conditions. The Fécondation is thus external; the Autofécondation is rare.

Classification

According to ADW:

According to ITIS:

  • class Nuda Chun, 1879
  • class Tentaculata Eschscholtz, 1825
    • order Cestida Gegenbaur, 1856
    • order Cydippida
    • order Lobata Eschscholtz, 1825
    • order Platyctenida Bourne, 1900
    • order Thalassocalycida Madin and Harbison, 1978

According to NCBI:

  • class Cyclocoela
  • class Typhlocoela
    • order Cydippida
    • order Platyctenida

References

Millets E.C. (1998). Ctenophora phylum: list off all valid species names

External bonds

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