Limnognathia maerski

from Wikipedia, the free encyclopedia
Limnognathia maerski
Limnognathia maerski.PNG

Limnognathia maerski

Systematics
Trunk : Micrognathozoa
Class : not classified
Order : not classified
Family : not classified
Genre : Limnognathia
Type : Limnognathia maerski
Scientific name
Limnognathia maerski
Kristensen & Funch , 2000

Limnognathia maerski is a kind of multicellular animals within the flatworm-like . It is the only species inthe Micrognathozoa tribe ( Gr .: creatures with small pines ). This strain is a higher-ranking taxon that was only newly introduced in 2000. Limnognathia maerski are very small, worm-shaped animals under half a millimeter long.

Systematics

The highly complex jaw formation of the species suggested that it belonged to the large Gnathifera group introduced five years before Limnognathia maerski was first described . The first molecular genetic test results for this relationship hypothesis were published in 2004 by Giribet et al. submitted, but did not provide clear support for Limnognathia maerski's membership in this group. According to Giribet et al. for Limnognathia to accept at least a very independent position, so it is not about a Verzwergungsform within another group. This independent position would justify the introduction of a new high-ranking taxon Micrognathozoa for Limnognathia , even if its exact relationship remains unclear for the time being. A study from 2015 actually suggests, based on genetic data, a sister group relationship to the rotifers (Rotifera, now mostly called Syndermata, including the scratchworms ). The common sister group of both would be the Kiefermündchen or Gnathostomulida. Accordingly, the Gnathifera would be justified as a taxon.

features

Limnognathia maerski has a combination of characteristics that make it impossible to integrate the animal into one of the previously known strains within the multicellular cell.

In addition to the immobile cilia , which are used for sensory perception, there are various arrangements of eyelashes, which are used for locomotion and the tumbling of food. These sit on the front of the abdomen and on the side of the head region as well as on the thorax and abdomen. The anterior region eyelashes are arranged in horseshoe-shaped rows. Their job is to swirl food particles into the mouth opening. The cilia on the side of the mouth opening and on the stomach side of the body are arranged differently. These are mostly in two rows, brush-shaped, in groups across the body axis. Each group comes from a single cell. Such cells are called ciliophores and otherwise only occur in the animal kingdom in the microscopic little bristles from the families Diurodrilidae and Neotenotrocha . Four ciliophores are arranged laterally next to the mouth opening. The ciliophores on the ventral side of the body form two long rows along the axis of the body. All the eyelashes of a cell beat in the same rhythm, so that Limnognathia maerski can move forward as if with comb-like feet.

The jaw apparatus consists of 15 parts connected by muscles and ligaments. These individual jaw structures are between 4 and 14 micrometers in size. They comprise various mouthparts that can move relative to one another and are partially provided with teeth. Like the rotifers and the Gnathostomulida, the jaws are called “Trophi”. Although the structure of the jaws of Limnognathia maerski differs greatly from the other groups, studies of the ultrastructure with the transmission electron microscope (TEM) have shown that, like the rotifers and the Gnathostomulida, they are composed of tightly packed rods. As a synapomorphism, this feature would speak for a phylogenetic relationship of the three groups and support the combination of a main Gnathifera tribe .

Research history

Limnognathia maerski was first discovered in 1994 by a group of students from the University of Copenhagen under the direction of Professor Reinhardt Kristensen in a freshwater spring near the Danish Arctic station on Disko Island in western Greenland . The group actually wanted to study the marine meiofauna on the island's beaches. Fresh water from the nearby spring was used to filter out the marine microorganisms. The organisms found in it were determined beforehand in order to be able to distinguish them from marine organisms. In addition to various rotifers , a species was observed that differed from the rotifers in the type of swimming movement. It soon became clear that the new species could crawl over moss leaves with the help of cilia placed on the belly side. Rotifers do not know this way of locomotion. Even under the light microscope, organs that are not found in rotifers can be seen at high magnification.

Some specimens of the new species were brought to the laboratory of the Zoological Museum in Copenhagen and examined under the electron microscope . It turned out that the jaw apparatus of Limnognatha maerski differs significantly from other animal groups, and a new taxonomic group called Micrognathozoa was set up, but so far only includes one species.

The species has now also been found on the sub-Antarctic Crozet Islands .

literature

  • FW Harrison: Description of Limnognathia maerski. in Journal of Morphology Vol. 246, No. 1, October 2000. Pages 50-52, PMID 11015716
  • BA Young, K. Zahn, M. Blair and J. Lalor: Micrognathozoa: A new class with complicated jaws like those of rotifera and Gnathostomulida. in Journal of Morphology Vol. 246, No. 3, October 2000. Page 260, PMID 11077436
  • Martin Vinther Sørensen: Further structures in the jaw apparatus of Limnognathia maerski (Micrognathozoa), with notes on the phylogeny of the Gnathifera. in Journal of Morphology Vol. 255, No. 2, 2003. Pages 131-45, PMID 12474262
  • Reinhardt Møbjerg Kristensen and Peter Funch: Micrognathozoa: a new class with complicated jaws like those of Rotifera and Gnathostomulida. in Journal of Morphology Vol. 246, No. 1, October 2000. Pages 1-49, PMID 11015715
  • Gonzalo Giribet, Martin Vinther Sørensen, Peter Funch, Reinhardt Møbjerg Kristensen and Wolfgang Sterrer: Investigations into the phylogenetic position of Micrognathozoa using four molecular loci. in Cladistics Vol. 20, No. 1, February 2004. Pages 1ff doi : 10.1111 / j.1096-0031.2004.00004.x
  • WH De Smet: A new record of Limnognathia maerski Kristensen & Funch, 2000 (Micrognathozoa) from the subatlantic Crozet Islands, with redescription of the trophi. in Journal of Zoology Vol. 258, London 2002. Pages 381-393
  • Martin Vinther Sørensen, Peter Funch, E. Willerslev, AJ Hansen and J. Olesen: On the phylogeny of Metazoa in the light of Cycliophora and Micrognathozoa. in Zoologischer Anzeiger Vol 239, 2000. Pages 297-318

Web links

Individual evidence

  1. Christopher E. Laumer, Nicolas Bekkouche, Alexandra Kerbl, Freya Goetz, Ricardo C. Neves, Martin V. Sørensen, Reinhardt M. Kristensen, Andreas Hejnol, Casey W. Dunn, Gonzalo Giribet, Katrine Worsaae (2015): Spiralian Phylogeny Informs the Evolution of Microscopic Lineages. Current Biology 25: 2000-2006. doi : 10.1016 / j.cub.2015.06.068