Arcellinida


Arcellinid testate amoebae or Arcellinida, Arcellacean or lobose testate amoebae are single-celled protists partially enclosed in a simple test.
Arcellinid testate amoebae are commonly found in soils, leaf litter, peat bogs and near/in fresh water. They use their pseudopodia, a temporary cell extension, for moving and taking in food. Like most amoebae, they are generally believed to reproduce asexually via binary fission. However a recent review suggests that sexual recombination may be the rule rather than the exception in amoeboid protists in general, including the Arcellinid testate amoebae.

Test or shell

Simple tests are made by secretion, agglutination of foreign material, or sometimes a combination of both. Past environmental changes can be determined by analysing the composition of fossil tests, including the reconstruction of past climate change. Testate amoebae species have been used to reconstruct hydrological changes over the late Holocene, as a result of individual species possessing a narrow tolerance for ecohydrological conditions such as water-table depth or pH.

Evolutionary history

Fossils of arcellinid testate amoebae date back to the Cryogenian period.
Testate amoebae are theorized to be mostly polyphyletic, but testaceafilosea, one group of testate amoebae, are theorized to be monophyletic. Ancient tests of terrestrial fauna are commonly found in fossilized amber, although mid-Cretaceous testate amoeba have been found in ancient lake sediments. It is likely that the group has evolved minimally over the course of the Phanerozoic.

Classification

The group contains the following taxa:
incertae sedis: