Macrostomorpha

Article By:

Rieger, Reinhard Institute of Zoology and Limnology, University of Innsbruck, Innsbruck, Austria.

Last reviewed:August 2020

DOI:https://doi.org/10.1036/1097-8542.801650

More than 300 species of small (mostly 1 mm size) flatworms usually with a ventral mouth situated about one quarter distant from the rostral tip of the body. A ciliated tubular foregut leads into a ciliated gut. Except for the Haplopharyngida, an anus is lacking. A hindgut is never differentiated. Macrostomorpha are covered by a single-layered, ciliated epidermis; they move by ciliary gliding and have special duo-gland adhesive papillae, at least in the tail region, which they use for temporary adhesion to and quick release from the substrate (only the marine, pelagic microstomid Alaurina does not possess papillae). The space between epidermis and gut is filled with parenchymal cells and muscle cells among others. The animals are hermaphroditic; sexual reproduction is typical. Larval stages are not known. Many species are found in marine sand and mud, and in various freshwater habitats. These flatworms were formerly members of the Turbellaria-Rhabdocoela, but are now included in the Rhabditophora, which is one of three monophyletic taxa constituting the Platyhelminthes (Acoelomorpha, Catenulida, and Rhabditophora). See also: Platyhelminthes

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