The euglyphids are a prominent group of filose amoebae that produce shells or tests that in most described species is reinforced by siliceous scales, plates, and sometimes spines, but this reinforcement is absent in other species.[2]
These elements are created within the cell and then assembled on its surface in a more or less regular arrangement, giving the test a textured appearance. There is a single opening for the long slender pseudopods, which capture food and pull the cell across the substrate.
Euglyphids are common in soils, marshes, and other organic-rich environments, feeding on tiny organisms such as bacteria. The test is generally 30–100 μm in length, although the cell only occupies part of this space. During reproduction a second shell is formed opposite the opening, so both daughter cells remain protected. Different genera and species are distinguished primarily by the form of the test. Euglypha and Trinema are the most common.
The euglyphids are traditionally grouped with other amoebae. However, genetic studies instead place them with various amoeboid and flagellate groups, forming an assemblage called the Cercozoa. Their closest relatives are the thaumatomonads, flagellates that form similar siliceous tests.
Photosynthetic species are found in the genera Paulinella and Placocista. The photosynthetic abilities in Paulinella comes from an event when a cyanobacterium settled permanently within the cell. In Placocista, where a few species have colonies of symbiotic Chlorella living inside them, the relationship is less intimate. The photosynthetic Paulinella are phototrophic, and the photosynthetic Placocista are mixotrophic.[3][4][5]
Phylogeny based on Chatelain et al. 2013[6]
Paulinellidae de Saedeleer 1934 emend. Adl et al. 2012
Cyphoderiidae de Saedeleer 1934
Tracheleuglypha Deflandre 1928
Assulinidae Lara et al. 2007
Euglyphidae Wallich 1864 emend Lara et al. 2007
Sphenoderiidae Chatelain et al. 2013
Trinematidae Hoogenraad & De Groot 1940 emend Adl et al. 2012
Order Euglyphida Copeland 1956 emend. Cavalier-Smith 1997[7]