Catenulida

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Catenulida
Catenula lemnae
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Catenulida
Meixner, 1924[1]
Families
Synonyms

Notandropora Reisinger, 1924

Catenulida is an order of

flatworms in the classical classification, or a class of flatworms in a phylogenetic approach.[2] They are relatively small free-living flatworms, inhabiting freshwater and marine environments. There are about 100 species described worldwide, but the simple anatomy makes species distinction problematic.[2]

Description

The anatomy of catenulids is simple and lacks hard parts. The mouth is located anteriorly and connects to a simple

protonephridium.[2]

The

flagella or cilia.[2] Asexual reproduction by paratomy is common, and it usually leads to a chain of organisms (zooids), hence the name, from Latin catenula, small chain.[2]

Members of the

digestive tract, and instead harbor intracellular chemoautotrophic bacterial symbionts that are assumed to provide their nutrition.[3][4]

Ecology

All catenulids are aquatic, benthic animals. Most of them live in freshwater, being usually very abundant in mires, ponds, streams and moist terrestrial habitats. A small number of species are known to live in the sea.[5]

The diet of most catenulids consists of small invertebrates and algae that they capture from the water column.[6] Others, such as those of the genus Paracatenula use chemoautotrophic bacterial symbionts that live inside their cells as a food source.[3]

Phylogeny

The monophyly of Catenulida is supported by molecular studies and by at least three synapomorphies: the unpaired protonephridium, the unpaired and anterodorsally located testis and the nonmobile sperm.[7]

Although there are no known synapomorphies connecting Catenulida to other flatworms (Rhabditophora), molecular studies indicate that they are sister-groups. All characters common to both clades, such as the internal fertilization and the simple gut with a single opening, are found in other groups as well.[2]

References

  1. ^ Artois, T.; Tyler, S. (2015). Catenulida. In: Tyler, S., Artois, T.; Schilling, S.; Hooge, M.; Bush, L.F. (eds) (2006-2017). World list of Platyhelminthes. Accessed through: World Register of Marine Species at [1] on 2017-02-14
  2. ^
    doi:10.1016/j.ode.2008.09.002
    .
  3. ^
    PMID 22131640
    .
  4. PMID 21709249
    .
  5. ISSN 1439-6092.Open access icon
  6. ISSN 1723-8633.Open access icon
  7. ISSN 2236-3777.Open access icon
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