Foraminifera (forams for short) are single-celled protists with shells. Their shells are also referred to as tests because in some forms the protoplasm covers the exterior of the shell. The shells are commonly divided into chambers which are added during growth, though the simplest forms are open tubes or hollow spheres. Depending on the species, the shell may be made of organic compounds, sand grains and other particles cemented together, or crystalline calcite.
A typical foram : In the picture about, the dark brown structure is the test, or shell, inside which the foram lives. Radiating from the opening are fine hairlike reticulopodia, which the foram uses to find and capture food.
Fully grown individuals range in size from about 100 micrometers to almost 20 centimeters long. A single individual may have one or many nuclei within its cell. The largest living species have a symbiotic relationship with algae, which they "farm" inside their shells. Other species eat foods ranging from dissolved organic molecules, bacteria, diatoms and other single celled phytoplankton, to small animals such as copepods. They move and catch their food with a network of thin extensions of the cytoplasm called reticulopodia, similar to the pseudopodia of an amoeba, although much more numerous and thinner.
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For more information about foraminifera :
Try the Gulf of St. Lawrence Database, including images and information on Late Quaternary microfossils.
Click here to see images of some type specimens from the UCMP microfossil collections.