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🔎 Foraminifera – Definition and Explanations


Domain Eukaryota
Reign Chromalveolata
Division (Division is a law of composition which associates the product of the first with two numbers…) Rhizaria
Super embr. Retaria
d’Orbigny, 1826
Classes of rank ( Mathematics In linear algebra, the rank of a family of vectors is the dimension of the…) inferior
  • Athalamea
  • Polythalamea
  • Xenophyophorea
  • Schizocladea
Phylogenetic position
  • Eukaryota
    • clade “SAR”
      • Stramenopiles
      • Rhizaria
      • Alveolata

The foraminifera are protozoa that appeared in Cambrian (The Cambrian, which extends from -542 ± 0.3 to…). The test (sometimes called, incorrectly, shell), comprising one or more chambers (or locus Where lodges), is provided with one or more foramen (orifice). They have a way of life (Life is the name given 🙂 benthic (on and in the sediment) or planktonic (in the column ofwater (Water is a ubiquitous chemical compound on Earth, essential for all…), and particularly in the photic zone). Their size generally varies from 38 µm to 1 mm (some can be over 10 cm). Their diet (For the cultural diets practiced by Man see practice…) is made of bacteria (Bacteria (Bacteria) are prokaryotic unicellular living organisms, characterized…)algae, mollusc larvae, shellfish (Crustaceans (Crustacea) are arthropods, i.e. animals whose bodies…)various wastes.

Story of their discovery

Plate from a book by d’Orbigny representing Foraminifera

It was in 1826 that Alcide Dessalines d’Orbigny (1802-1857) created the order of foraminifera in a work entitled Methodical table of the class of cephalopods. During his lifetime, Orbigny would describe 1,500 species, most of them new to the science (Science (Latin scientia, “knowledge”) is, according to the dictionary…). He was the first to study their way of life and ecological requirements. But the unicellular nature of foraminifera was discovered by Félix Dujardin (1801-1860) in 1835. It was thanks to their study that he discovered the protoplasm of unicellular organisms.

The basics of classification

The composition of this test (organic, agglutinated, carbonated and siliceous) is the main classification criterion for foraminifera and is the basis of most classifications, including that of Loeblich and Tappan (1964 and 1988). Foraminifera at organic tests are mainly represented by unicellular foraminifera, the Allogromiina (suborder). This suborder is still poorly known since, due to its loss in fossil assemblages, micropaleontologists have studied them very little. However, currently the Gooday Group in Southampton (UK) is trying to catch up, everything (The whole understood as the whole of what exists is often interpreted as the world or…) at least, on their recognition. Foraminifera at clumped tests are characterized by the agglutinate of grains taken from the sediment (cf. Gaudryina sp., foraminifer at bottom left on the proposed plate). Grain selection could occur in some species (eg Saccammina micaceus, which presents only mica grains). Two types of foraminifera carbonate tests can be differentiated. The porcelanés have an aspect White (White is the color of a body heated to about 5000°C (see…) opaque, while hyaline ones are transparent and glassy. Finally, the foraminifera siliceous tests are extremely rare. The second classification criterion is the layout of the dressing rooms. Thus, we can distinguish several main types of tests:

  • unilocular tests;
  • plurilocular tests:
    • serial tests, the boxes are organized in series (eg Gaudryina sp.);
    • spiral tests (like snails; the other three examples on the board);
    • discoid tests;
    • milioliform tests. The lodges are formed successively and individually in several planes;
    • complex testing.

A third criterion is the ornamentation of the test. The test may be smooth, but often has growths (ribs, spines, suture bridges, etc.) and depressions. Finally, a fourth criterion is the morphology of the main opening and its position. Thus, the opening is sometimes related to additional elements (teeth, lips, plates, etc.) and/or to the end of a neck.

Microfossils (Microfossils are small-sized fossils, the study of which requires resources…) marine sediments containing radiolarians (spheres), sponge spicules (small “spines”), planktonic foraminifera (small white shells) and benthic foraminifera (large white shell in the center of the image, as well as the small shells yellow made up of agglomerated grains of sand). the diameter (In a circle or a sphere, the diameter is a line segment passing through the center…) average of the spheres is about 0.5 mm. Sample (Generally speaking, a sample is a small amount of material, information, or…) from washed and sieved sediments at 125 µm (east of the sea (The term sea covers several realities.) from Weddell, Antarctica).

Potential use of recent foraminifera

Omnipresent in marine environments, they occupy a large number of ecological niches (from swamp (In geography, a marsh is a type of landscape formation, with little relief…) maritime to abyssal plains). Due to their short life cycle (1 to 3 month (The month (From lat. mensis “month”, and formerly in plural “menses”) is a period of time…) in mean (The average is a statistical measure characterizing the elements of a set of…)1 year maximum), foraminifera react quickly to changes in their environment (The environment is everything that surrounds us. It is all the natural elements and…). Their populations can increase or decrease, their variety can change, the cells can grow or shrink… pollution (Pollution is defined as what makes an environment unhealthy. The definition varies by…) and environmental changes (eg climatic variations) can thus lead to a radical transformation of foraminifera populations. Thus, their short life cycle and their ubiquity in the marine environment, associated with great richness in the sediment (analyzes statistics (Statistics is both a formal science, a method and a technique. It…) robust), an inexpensive and easy method of analysis and a trace (TRACE is a NASA space telescope designed to study the connection between the…) in the fossil (A fossil (derived from the noun of the Latin verb fodere: fossil, literally…) (allows the study before modification of the environment) make foraminifera, in particular benthic ones, good bio-indicators of the quality of the environment or proxies of environmental changes.