Arcellinidtestate amoebae orArcellinida,[1]Arcellacean[2] orlobose testate amoebae[3] are single-celledprotists partially enclosed in a simpletest (shell).
Arcellinid testate amoebae are commonly found in soils,leaf litter, peat bogs and near/in fresh water.[1] They use theirpseudopodia, a temporary cell extension, for moving and taking in food. Like most amoebae, they are generally believed toreproduce asexually via binary fission. However a recent review suggests that sexual recombination may be the rule rather than the exception inamoeboid protists in general, including the Arcellinid testate amoebae.[4]
Lobopodia, a pseudopod or arm-like projection made of cytoplasm
Prey (not to scale)
Arcellinida always have a shell or testa. The tests lie outside the cell membrane and consist of organic or mineral materials that are either secreted or incorporate external particles. The testa has a single main opening.[5]
Simple tests are made by secretion (autogenous tests), agglutination of foreign material (xenogenous tests), or sometimes a combination of both. Past environmental changes can be determined by analysing the composition of fossil tests, including the reconstruction of pastclimate change.[1] Testate amoebae species have been used to reconstruct hydrological changes over the lateHolocene, as a result of individual species possessing a narrow tolerance for ecohydrological conditions such as water-table depth or pH.[6]
Fossils of arcellinid testate amoebae date back to theTonian stage of theProterozoic, around 789-759 million years ago. The fossils indicate that by 730 million years ago, arcellinids had already diversified into major lineages.[7]
Testate amoebae are theorized to be mostlypolyphyletic (coming from more than one ancestral type), but testaceafilosea, one group of testate amoebae, are theorized to bemonophyletic. Ancient tests of terrestrial fauna are commonly found in fossilized amber,[8] although mid-Cretaceous testate amoeba (i.e.,Diffligia,Cucurbitella) have been found in ancient lake sediments.[9] It is likely that the group has evolved minimally over the course of thePhanerozoic.
^abAdl SM, Simpson AG, Lane CE, Lukeš J, Bass D, Bowser SS, Brown MW, Burki F, Dunthorn M, Hampl V, Heiss A, Hoppenrath M, Lara E, le Gall L, Lynn DH, McManus H, Mitchell EA, Mozley-Stanridge SE, Parfrey LW, Pawlowski J, Rueckert S, Shadwick L, Schoch CL, Smirnov A, Spiegel FW (2012)."The Revised Classification of Eukaryotes".Journal of Eukaryotic Microbiology.59 (5):429–514.doi:10.1111/j.1550-7408.2012.00644.x.PMC3483872.PMID23020233.
^Woodland, Wendy, A. (1998). "Quantitative estimates of water tables and soil moisture in Holocene peatlands from testate amoebae".The Holocene.8 (3):261–273.doi:10.1191/095968398667004497.S2CID128897334.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Ralf Meisterfeld:Arcellinida, In: John J. Lee, Gordon F. Leedale, Phyllis Bradbury (Hrsg.): Illustrated Guide to the Protozoa, 2nd Edition. Vol. 2, Society of Protozoologists, Lawrence, Kansas 2000,ISBN1-891276-23-9, pp. 827-860
