Seriata
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The Seriata is an order of the vortex worms that belong to the flatworms . The vortex worms are free-living flatworms that feed predatory. The group of Seriata includes the widespread subordination of Tricladida with the most famous free-living flatworms, which also include the European stream planaria ( Dugesia gonocephala ). In addition, there is the subordination of the Proseriata , which contains less known and well-studied representatives.
features
The Seriata got their name from the serially created gonads , by which they are differentiated from the other whirlpool worms in the modern system. Like all flatworms, they have a flattened physique, but are rather elongated and thus resemble the other free-living worms more than other orders of the vortex worms.
Way of life
The Seriata are marine and widespread in fresh water, but have also conquered the land where they live in a humid environment, e.g. B. in the tropical rainforests, and were introduced by humans at the roots of plants in greenhouses and terrariums. Based on these ecological aspects, the order of the Tricladida was divided by Hallez in 1892 into the infraorders of marine planariums (Maricola), freshwater planariums (Paludicola) and land planariums (Terricola).
Systematics
The morphological features of the order suggest a monophyletic group. Recent studies of the ultrastructure of the excretory organs have shown, however, that the Proseriata have an original organization of the protonephridia , the Tricladida a more developed, derived structure. Phylogenetic studies place the Proseriata at the basis of the parasitic living orders of the flatworms (including the tapeworms and liver fluke ), which are summarized under the name Neodermata . The Seriata are therefore likely to be paraphyletic.
The Tricladida get their name from the three main branches of their intestinal tract, which, like all flatworms, does not contain its own excretory opening. Digestive products are released through the pharynx and the mouth opening. The infraorders of the Tricladida are groups put together according to ecological criteria. Only the Maricola are monophyletic, their sister group consists of the Paludicola and the Terricola. However, these two groups are probably paraphyletic, since one family of freshwater planarians, the Dugesiidae, is more closely related to land planarians from a molecular genetic point of view than to the other two families of freshwater planarians ( Planariidae and Dendrocoelidae ).
literature
- Salvador Carranza, D. Timothy J. Littlewood, Karen A. Clough, Inaki Ruiz-Trillo, Jaume Baguna, Marta Riutort: A Robust Molecular Phylogeny of the Tricladida (Platyhelminthes: Seriata) with a Discussion on Morphological Synapomorphies. Proceedings: Biological Sciences, Vol. 265, No. 1396, pp. 631-640, Royal Society of London, April 7, 1998