Foraminifera

Foraminifera are a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses, and commonly an external shell (called a "test") of diverse forms and materials. Tests of chitin are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the seafloor sediment (benthic), while a smaller variety float in the water column at various depths (planktonic). Fewer are known from freshwater or brackish conditions, and some very few (nonaquatic) soil species have been identified through molecular analysis of small subunit ribosomal DNA.

Classification

Foraminifera are typically classified by their test structure and wall composition. The traditional classification is based on tests having one or multiple chambers; some foraminifera lack a test, which makes them difficult to classify.

Morphology

Foraminifera tests 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 test is made of silica, agglutinated sediment particles, or secreted calcite or aragonite.

Ecology

Foraminifera are found in all marine environments, from the intertidal to the deepest ocean trenches, and from the tropics to the poles. They are an important part of the marine food chain, being preyed upon by small metazoans, and are hosts to a variety of symbionts.

Fossil Record

Foraminifera have an excellent fossil record, with their hard shells (tests) preserved in sedimentary rocks. They first appeared in the Early Cambrian period, and their diversity has been used as a tool for biostratigraphy.

See Also

• Amoeboid protists
• Marine environments
• Fossil record
• Biostratigraphy

Foraminifera Resources
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