Plumbing the depths infocus #76 December 2024

In a previous article (infocus 70 pp. 4 - 15) I described some amazing structures produced by single-cell amoeba known as diatoms. Their sub-microscopic, silica shells became very popular microscope specimens in the 19th Century, and a large number of carefully mounted slides survive today, some of which are keenly sought-after.

DOI: 10.22443/rms.inf.1.278

Another class of unicellular creatures occurs, foraminifera, that are found from the bottom of the deepest oceans right up to intertidal zones. They also occur as prolific micro-fossils in chalk and limestone.

The huge chalk cliffs in Southern England are made up almost entirely of foraminifera shells, known as tests, which consist mainly of calcium carbonate. They are also important indicators in oil exploration, where careful study of rock cores can reveal likely oil deposits.

In contrast to the microscopic diatoms, most foraminifera tests are in the range 20 to ~ 200 micrometers in size, although some, found in the deepest ocean depths and also as fossils, may be up toseveral cm in size. And remember, these are the homes of single-cell organisms!

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