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Foraminifera (;
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
for "hole bearers"; informally called "forams") are single-celled organisms, members of a
phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclatu ...
or
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...
of
amoeboid An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the e ...
s characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell (called a "
test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...
") of diverse forms and materials. Tests of
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
(found in some simple genera, and
Textularia ''Textularia'' is a genus of textulariid foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ...
in particular) are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the
seafloor sediment Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, main ...
(i.e., are
benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
), while a smaller number float in the water column at various depths (i.e., are
plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cr ...
ic), which belong to the suborder
Globigerinina The Globigerinina is a suborder of foraminiferans that are found as marine plankton. They produce hyaline calcareous tests, and are known as fossils from the Jurassic period onwards. The group has included more than 100 genera and over 400 sp ...
. 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 Ribosomal DNA (rDNA) is a DNA sequence that codes for ribosomal RNA. These sequences regulate transcription initiation and amplification, and contain both transcribed and non-transcribed spacer segments. In the human genome there are 5 chrom ...
. Foraminifera typically produce a
test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...
, or shell, which can have either one or multiple chambers, some becoming quite elaborate in structure. These shells are commonly made of calcium carbonate () or agglutinated sediment particles. Over 50,000 species are recognized, both living (6,700–10,000)Ald, S.M. ''et al''. (2007
Diversity, Nomenclature, and Taxonomy of Protists
''Syst. Biol.'' 56(4), 684–689, DOI: 10.1080/10635150701494127.
and
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
(40,000). They are usually less than 1 mm in size, but some are much larger, the largest species reaching up to 20 cm. In modern scientific English, the term ''foraminifera'' is both singular and plural (irrespective of the word's
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
derivation), and is used to describe one or more specimens or taxa: its usage as singular or plural must be determined from context. Foraminifera is frequently used informally to describe the group, and in these cases is generally lowercase.


History of study

The earliest known reference to foraminifera comes from
Herodotus Herodotus ( ; grc, , }; BC) was an ancient Greek historian and geographer from the Greek city of Halicarnassus, part of the Persian Empire (now Bodrum, Turkey) and a later citizen of Thurii in modern Calabria ( Italy). He is known for ...
, who in the 5th century BCE noted them as making up the rock that forms the
Great Pyramid of Giza The Great Pyramid of Giza is the biggest Egyptian pyramid and the tomb of Fourth Dynasty pharaoh Khufu. Built in the early 26th century BC during a period of around 27 years, the pyramid is the oldest of the Seven Wonders of the Ancient Wor ...
. These are today recognized as representatives of the genus ''Nummulites''. Strabo, in the 1st Century BCE, noted the same foraminifera, and suggested that they were the remains of
lentil The lentil (''Lens culinaris'' or ''Lens esculenta'') is an edible legume. It is an annual plant known for its lens-shaped seeds. It is about tall, and the seeds grow in pods, usually with two seeds in each. As a food crop, the largest pro ...
s left by the workers who built the pyramids.
Robert Hooke Robert Hooke FRS (; 18 July 16353 March 1703) was an English polymath active as a scientist, natural philosopher and architect, who is credited to be one of two scientists to discover microorganisms in 1665 using a compound microscope that h ...
observed a foraminifera under the microscope, as described and illustrated in his 1665 book ''
Micrographia ''Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses. With Observations and Inquiries Thereupon.'' is a historically significant book by Robert Hooke about his observations through various lenses. It ...
:''
I was trying several small and single Magnifying Glasses, and casually viewing a parcel of white Sand, when I perceiv'd one of the grains exactly shap'd and wreath'd like a Shell ..I view'd it every way with a better Microscope and found it on both sides, and edge-ways, to resemble the Shell of a small Water-Snail with a flat spiral Shell ../blockquote> Antonie van Leeuwenhoek described and illustrated foraminiferal tests in 1700, describing them as minute cockles; his illustration is recognizable as being ''
Elphidium ''Elphidium'' is an abundant genus of foraminifera. Species can be found from coastal regions out to the continental slope, and in all temperature ranges. Like other forams, fossils from different species are used to date rocks. The taxonomy of ...
''. Early workers classified foraminifera within the genus ''
Nautilus The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species ...
'', noting their similarity to certain
cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...
s. It was recognised by
Lorenz Spengler Lorenz Spengler (22 September 1720 – 20 December 1807) was a Danish turner and naturalist. Born in Schaffhausen, Switzerland he arrived at Copenhagen in 1743 and became a tutor to Christian VI of Denmark and later Frederick V of Denmark in ...
in 1781 that foraminifera had holes in the septa, which would eventually grant the group its name. Spengler also noted that the septa of foraminifera arced the opposite way from those of nautili and that they lacked a nerve tube.
Alcide d'Orbigny Alcide Charles Victor Marie Dessalines d'Orbigny (6 September 1802 – 30 June 1857) was a French naturalist who made major contributions in many areas, including zoology (including malacology), palaeontology, geology, archaeology and anthrop ...
, in his 1826 work, considered them to be a group of minute
cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...
s and noted their odd morphology, interpreting the pseudopodia as tentacles and noting the highly reduced (in actuality, absent) head. He named the group ''foraminifères'', or "hole-bearers", as members of the group had holes in the divisions between compartments in their shells, in contrast to
nautili The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in ...
or
ammonites Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttle ...
. The protozoan nature of foraminifera was first recognized by
Dujardin Dujardin is a French surname, meaning "from the garden", and may refer to: * Charlotte Dujardin, British dressage rider * Édouard Dujardin, French writer * Félix Dujardin (1801–1860), French biologist * Jean Dujardin, French actor and comedian ...
in 1835. Shortly after, in 1852, d'Orbigny produced a classification scheme, recognising 72 genera of foraminifera, which he classified based on test shape—a scheme that drew severe criticism from colleagues. H.B. Brady's 1884 monograph described the foraminiferal finds of the ''Challenger'' expedition. Brady recognized 10 families with 29 subfamilies, with little regard to stratigraphic range; his taxonomy emphasized the idea that multiple different characters must separate taxonomic groups, and as such placed agglutinated and calcareous genera in close relation. This overall scheme of classification would remain until Cushman's work in the late 1920s. Cushman viewed wall composition as the single most important trait in classification of foraminifera; his classification became widely accepted but also drew criticism from colleagues for being "not biologically sound". Geologist
Irene Crespin Irene Crespin (12 November 1896 – 2 January 1980) was an Australian geologist and micropalaeontologist. Irene's interest in geology brought her attention to Frederick Chapman, who was a palaeontologist at the National Museum of Victoria. Iren ...
undertook extensive research in this field, publishing some ninety papers—including notable work on foraminifera—as sole author as well as more than twenty in collaboration with other scientists. Cushman's scheme nevertheless remained the dominant scheme of classification until Tappan and Loeblich's 1964 classification, which placed foraminifera into the general groupings still used today, based on microstructure of the test wall. These groups have been variously moved around according to different schemes of higher-level classification. Pawlowski's (2013) use of molecular systematics has generally confirmed Tappan and Loeblich's groupings, with some being found as polyphyletic or paraphyletic; this work has also helped to identify higher-level relationships among major foraminiferal groups.


Taxonomy

The taxonomic position of the Foraminifera has varied since Schultze in 1854, who referred to as an order, Foraminiferida.