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Frustule

The cell wall of a diatomic silicate cell is often referred to as a frustule. This cell wall has two overlapping halves to provide the cell with room to grow and to move a little. When a diatom cell divides into two daughter cells, each half keeps one of the pieces of the frustule of the original cell, and then grows a new half or valve within it. Because of this, each division cycle means the size of the cells gets smaller, and the cell must grow considerably before it is ready to divide again.

Diatoms, which bear frustules, are a eukaryotic algae classified with phytoplankton. They are unicellular but can join together to form colonies. The silicate walls making up the frustule can take a wide variety of shapes and appearances, some very beautiful and ornate. The many species (estimated 100,000 species) we know of live in the ocean with other plankton. They can live freely in open water or form a surface film at the water-sediment border. Diatoms probably make up 45% of the available protein in the ocean.

Because of the frustule, most diatom species are nonmobile, but a few can use an oozing sort of motion to move minimally. Frustules are heavy, and diatoms would sink normally in the ocean water in which they live; they depend primarily on the action of wind on the upper waters to keep them suspended.

Web Resources On Frustule

Pseudo-nitzschia Valve Structure
Kingdom Protista

Book Resources On Frustule

A guide to the morphology of the diatom frustule by Horace G. Barber
Arachnoidiscus: An account of the genus comprising its history, distribution, development, and growth of the frustule, structure ... by Nicholas Edward Brown

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