Mediolus corona are a genus of arcellacea, or testate (shell-producing) amoebas. They are unicellular organisms that inhabit the soil and humus of freshwater and terrestrial bodies, from the poles to the tropics. They are distinguished by shells bearing a variable number of spiked hollow spines, as well as a tooth-like, crenulated (finely notched or scalloped) aperture. Carleton University’s Earth Sciences laboratory of Professor Timothy Patterson identified the genus Mediolus corona in 2014. Micro-fossil evidence of Mediolus corona tests (shells) have been recorded as far back as 720 million years. Amoebas have a genome that is a hundred times the size of the human genome. Mediolus corona are being used in molecular studies since there is uncertainty as to whether the different shapes of the tests are due to genetic differences or merely responses to different environmental conditions. Researchers are currently using DNA studies to resolve this uncertainty. These amoebas are also important bioindicators for eutrophication* and phosphorous and arsenic pollution. They have been used by scientists to reconstruct paleo-lacustrine (ancient lake) environments.
*Eutrophication is the excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes dense plant growth and death of animal life from lack of oxygen.
An individual [Mediolus] flows around, carrying its case with it. While doing this, it not only engulfs food particles but also sand grains that accumulate inside the amoeba as a large ball. When the time to reproduce arrives, the nucleus of the amoeba replicates its DNA to create two complete nuclei. The cytoplasm (the body material) then begins to divide, one nucleus going into each half, to form two independent organisms. One of these will inherit the existing house, but the other takes the ball of stones in its cytoplasm. As the two organisms are created, these stones move to the surface and arrange themselves as a new house.
Built by Animals (Oxford: Oxford University Press, 2007), 60.
Mediolus is being substituted for the original ‘Difflugia’ in Hansell’s text, as the genus had not yet been distinguished by Patterson until 2014.
Let me just add a small point: the number of people with any knowledge on these organisms worldwide is a few dozens and only a handful have really worked with them. Culturing them is the expertise of an even more restrictive group. And the vast majority of universities will have nobody really competent with the study of protists. The point I’m trying to make is that these are not only beautiful organisms but they are also functionally important in aquatic and terrestrial ecosystems and extremely diverse (as shown by recent environmental molecular studies). So this calls for a quantum leap forward in our efforts to study them and this starts with initiatives such as yours. So thank you very much and I wish you full success!
Prof. Edward Mitchell
Laboratory of Science Biology, Université de Neuchâtel, Switzerland
Mediolus corona is one of four listed artists in a group show titled The Amoebic Workshop: A Submerged Exhibition. Curated by art historian Astarte Rowe, this groundbreaking, experimental project presents the work of a microbial organism on an equal footing with the work of humans, and not as part of an artist’s artwork.
Links / Updates
Mediolus, a new genus of Arcellacea (Testate Lobose Amoebae) by R. Timothy Patterson, Article number: 17.2.28A
© Paleontological Society, July 2014. Palaeontologia Electronica website.
Patterson RT, Roe HM, Swindles GT (2012) “Development of an Arcellacea (testate lobose amoebae) based transfer function for sedimentary phosphorus in lakes.” Palaeogeogr Palaeoclimatol Palaeoecol 348–349:32–44 18.
Patterson RT, Lamoureux EDR, Neville LA, Macumber AL (2013) “Arcellacea (Testate Lobose Amoebae) as pH Indicators in a pyrite mine-acidified lake, Northeastern Ontario, Canada.” Microb Ecol 65:541–554.
Kumar A, Patterson RT (2000) “Arcellaceans (thecamoebians): newtoolsformonitoringlong-termandshort-termchangesinlake bottom acidity.” Environ Geol 39:689–697.
Nawaf A. Nasser & R. Timothy Patterson et al (2016) “Lacustrine Arcellinina (Testate Amoebae) as Bioindicators of Arsenic Contamination.” Microb Ecol 72:130–149.
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