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Limnognathia

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Title: Limnognathia  
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Subject: Platyzoa, Sea worm, Disko Island, Salinella, Acoelomorpha
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Limnognathia

Limnognathia
Scientific classification
Kingdom: Animalia
(unranked): Platyzoa
Phylum: Gnathifera
Class: Micrognathozoa
Order: Limnognathida
Family: Limnognathiidae
Genus: Limnognathia
Species: L. maerski
Binomial name
Limnognathia maerski
Kristensen & Funch, 2000

Limnognathia maerski is a microscopic animal, discovered living in homothermic springs on Disko Island, Greenland in 1994, that has variously been assigned as a Class (biology) or subphylum in the phylum Gnathifera or as a phylum in a Gnathifera superphylum, named Micrognathozoa. It is related to the rotifers and gnathostomulids, grouped together as the Gnathifera.[1][2] With an average length of one-tenth of a millimetre, it is one of the smallest animals known.

L. maerski has very complicated jaws, with fifteen separate elements. The parts of the jaw structure are connected by ligaments and muscles. The jaw parts are very small, ranging from 4 μm to 14 μm. The animal can extend part of its jaw structure outside its mouth while eating. It also extends much of its jaw structure outside of its mouth when it is regurgitating items that are indigestible. Its main diet is bacteria, blue-green algae and diatoms.

L. maerski has a large ganglion, or 'brain', in its head, and paired nerve cords extending ventrally (along the lower side of the body) towards the tail. Stiff sensory bristles made up of one to three cilia are scattered about the body. These bristles are similar to ones found on gnathostomulids, but up to three cilia may arise from a single cell in L. maerski, while gnathostomulids never have more than one cilium per cell.

Flexible cilia are arranged in a horseshoe-shaped area on the forehead, and in spots on the sides of the head and in two rows on the underside of the body. The cilia on the forehead create a current that moves food particles towards the mouth. The other cilia move the animal.

All specimens of L. maerski that have been collected have had male organs, and it is now theorized that the animals hatch as males and then become females.

Phylogeny

Cladogram[3] showing the relationships of Limnognathia:

Gnathifera

Gnathostomulida



Micrognathozoa



Acanthocephala


Rotifera




References

  1. ^ Kristensen RM (2002). "An Introduction to Loricifera, Cycliophora, and Micrognathozoa". Integr Comp Biol. 42 (3): 641–51.  
  2. ^ (Bisby FA, Roskov YR, Orrell TM, Nicolson D, Paglinawan LE, Bailly N, Kirk PM, Bourgoin T, Baillargeon G., eds). CD-ROM; Species 2000: Reading, UK.Species 2000 & ITIS Catalogue of Life: 2009 Annual ChecklistGordon, Dennis P. (2009). "Towards a management hierarchy (classification) for the Catalogue of Life: Draft Discussion Document". In
  3. ^ Phylogeny from zmuc.dk
  • Comprehensive information on L. maerski
  • Science Now article on L. maerski
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