A Shelled Amoeba (Arcella vulgaris)
Family: Arcella Family (Arcellidae)
IUCN Conservation Status: Unassessed
The otherwise soft, squishy single-celled body of this common amoeba is enclosed in a concave brownish-yellow hemispherical shell known as a test, which is made up of chiton (the same material that forms the exoskeletons of insects) and protects it from both predators and adverse environmental conditions. Found in stagnant freshwater and damp soil throughout much of the world, a single hole in the shells of members of this species allows them to extend long, flexible "false feet" known as pseudopods out into their environment, which they use both to catch and ingest food (mainly algae and other smaller motile protists) and to drag themselves along surfaces, although when in water they are also capable of floating along by filling a bladder-like vacuole in their main cell body with gas. Like almost all single-celled organisms Arcella vulgaris reproduces asexually through binary fission (with a single adult cell dividing in two to produce "daughters". "Newborn" members of this species may initially lack shells, and if the shells of adults are too badly damaged they have been found to be capable of crawling out and surviving without protection for short periods as they grow a new one.
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Already included above, but a very cool little shell study: Here
