HOME

TheInfoList



OR:

Foraminifera (;
Latin Latin (, or , ) is a classical language belonging to the Italic languages, 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 ...
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 Nomenclatur ...
or class 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 pseudo ...
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 exclu ...
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 ...
), 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 cruci ...
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 chromos ...
. 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 languages, 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 ...
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 pyramids, Egyptian pyramid and the tomb of Fourth Dynasty of Egypt, Fourth Dynasty pharaoh Khufu. Built in the early 26th century BC during a period of around 27 years, the pyramid is the oldes ...
. These are today recognized as representatives of the genus ''Nummulites''.
Strabo Strabo''Strabo'' (meaning "squinty", as in strabismus) was a term employed by the Romans for anyone whose eyes were distorted or deformed. The father of Pompey was called "Pompeius Strabo". A native of Sicily so clear-sighted that he could see ...
, 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 produ ...
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 th ...
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 Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch microbiologist and microscopist in the Golden Age of Dutch science and technology. A largely self-taught man in science, he is commonly known as " the ...
described and illustrated foraminiferal tests in 1700, describing them as minute cockles; his illustration is recognizable as being '' Elphidium''. 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 in ...
'', 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, a ...
s. It was recognised by Lorenz Spengler 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, a ...
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 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 cuttlefish) ...
. 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 comedia ...
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 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. Loeblich (1987) and Tappan (1992) reranked Foraminifera as a class as it is now commonly regarded. The Foraminifera have typically been included in the
Protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
, or in the similar Protoctista or
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 exclu ...
kingdom Kingdom commonly refers to: * A monarchy ruled by a king or queen * Kingdom (biology), a category in biological taxonomy Kingdom may also refer to: Arts and media Television * ''Kingdom'' (British TV series), a 2007 British television drama s ...
. Compelling evidence, based primarily on
molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
, exists for their belonging to a major group within the Protozoa known as the
Rhizaria The Rhizaria are an ill-defined but species-rich supergroup of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many foramin ...
. Prior to the recognition of evolutionary relationships among the members of the Rhizaria, the Foraminifera were generally grouped with other
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 pseudo ...
s as phylum Rhizopodea (or Sarcodina) in the class Granuloreticulosa. The Rhizaria are problematic, as they are often called a "supergroup", rather than using an established
taxonomic rank In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in an ancestral or hereditary hierarchy. A common system consists of species, genus, family, order, class, phylum, kingdom, domain. Whi ...
such as
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 Nomenclatur ...
. Cavalier-Smith defines the Rhizaria as an infra-kingdom within the kingdom Protozoa. Some taxonomies put the Foraminifera in a phylum of their own, putting them on par with the amoeboid Sarcodina in which they had been placed. Although as yet unsupported by morphological correlates, molecular data strongly suggest the Foraminifera are closely related to the
Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major e ...
and
Radiolaria The Radiolaria, also called Radiozoa, are protozoa of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. The ela ...
, both of which also include amoeboids with complex shells; these three groups make up the Rhizaria. However, the exact relationships of the forams to the other groups and to one another are still not entirely clear. Foraminifera are closely related to testate amoebae.


Anatomy

The most striking aspect of most foraminifera are their hard shells, or tests. These may consist of one of multiple chambers, and may be composed of protein, sediment particles, calcite, aragonite, or (in one case) silica. Some foraminifera lack tests entirely. Unlike other shell-secreting organisms, such as
molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...
or
coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...
s, the tests of foraminifera are located inside the
cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...
, within the
protoplasm Protoplasm (; ) is the living part of a cell that is surrounded by a plasma membrane. It is a mixture of small molecules such as ions, monosaccharides, amino acid, and macromolecules such as proteins, polysaccharides, lipids, etc. In some defini ...
. The organelles of the cell are located within the of the test, and the of the test allow the transfer of material from the pseudopodia to the internal cell and back. The foraminiferal cell is divided into granular endoplasm and transparent ectoplasm from which a
pseudopodia A pseudopod or pseudopodium (plural: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filament ...
l net may emerge through a single opening or through many perforations in the test. Individual pseudopods characteristically have small granules streaming in both directions. Foraminifera are unique in having ''granuloreticulose pseudopodia''; that is, their pseudopodia appear granular under the microscope; these pseudopodia are often elongate and may split and rejoin each other. These can be extended and retracted to suit the needs of the cell. The pseudopods are used for locomotion, anchoring, excretion, test construction and in capturing food, which consists of small organisms such as diatoms or bacteria. Aside from the tests, foraminiferal cells are supported by a
cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is compose ...
of microtubules, which are loosely arranged without the structure seen in other amoeboids. Forams have evolved special cellular mechanisms to quickly assemble and disassemble microtubules, allowing for the rapid formation and retraction of elongated pseudopodia. In the gamont (sexual form), foraminifera generally have only a single nucleus, while the agamont (asexual form) tends to have multiple nuclei. In at least some species the nuclei are dimorphic, with the somatic nuclei containing three times as much protein and RNA than the generative nuclei. However, nuclear anatomy seems to be highly diverse. The nuclei are not necessarily confined to one chamber in multi-chambered species. Nuclei can be spherical or have many lobes. Nuclei are typically 30-50 µm in diameter. Some species of foraminifera have large, empty vacuoles within their cells; the exact purpose of these is unclear, but they have been suggested to function as a reservoir of nitrate. Mitochondria are distributed evenly throughout the cell, though in some species they are concentrated under the pores and around the external margin of the cell. This has been hypothesised to be an adaptation to low-oxygen environments. Several species of
xenophyophore Xenophyophorea is a clade of foraminiferans. Members of this class are multinucleate unicellular organisms found on the ocean floor throughout the world's oceans, at depths of . They are a kind of foraminiferan that extract minerals from their ...
have been found to have unusually high concentrations of radioactive isotopes within their cells, among the highest of any eukaryote. The purpose of this is unknown.


Ecology

Modern Foraminifera are primarily marine organisms, but living individuals have been found in brackish, freshwater and even terrestrial habitats. The majority of the species 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 ...
, and a further 50 morphospecies 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 cruci ...
ic. This count may, however, represent only a fraction of actual diversity, since many genetically distinct species may be morphologically indistinguishable. Benthic foraminifera are typically found in fine-grained sediments, where they actively move between layers; however, many species are found on hard rock substrates, attached to seaweeds, or sitting atop the sediment surface. The majority of planktonic foraminifera are found in the
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 ...
, a lineage within the
rotaliida The Rotaliida are an order of Foraminifera, characterized by multilocular tests (shells) composed of bilamellar perforate hyaline lamellar calcite that may be optically radial or granular. In form, rotaliid tests are typically enrolled, but ma ...
. However, at least one other extant rotaliid lineage, '' Neogallitellia'', seems to have independently evolved a planktonic lifestyle. Further, it has been suggested that some Jurassic fossil foraminifera may have also independently evolved a planktonic lifestyle, and may be members of Robertinida. A number of forams have unicellular
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular m ...
as
endosymbiont An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. (The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within" ...
s, from diverse lineages such as the
green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alga ...
,
red algae Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...
, golden algae,
diatom A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...
s, and
dinoflagellate The dinoflagellates ( Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates ...
s. These
mixotroph A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs com ...
ic foraminifers are particularly common in nutrient-poor oceanic waters. Some forams are kleptoplastic, retaining
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...
s from ingested algae to conduct
photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
. Most foraminifera are heterotrophic, consuming smaller organisms and organic matter; some smaller species are specialised feeders on
phytodetritus In oceanography, phytodetritus is the organic particulate matter resulting from phytoplankton and other organic material in surface waters falling to the seabed. This process takes place almost continuously as a " marine snow" of descending particl ...
, while others specialise in consuming diatoms. Some benthic forams construct feeding cysts, using the pseuodopodia to encyst themselves inside of sediment and organic particles. Certain foraminifera prey upon small animals such as
copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have p ...
s or cumaceans; some forams even predate upon other forams, drilling holes into the tests of their prey. One group, the xenophyophores, has been suggested to farm bacteria within their tests, although studies have failed to find support for this hypothesis.
Suspension feeding Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
is also common in the group, and at least some species can take advantage of
dissolved organic carbon Dissolved organic carbon (DOC) is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called partic ...
. A few foram species are
parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
, infecting sponges, molluscs, corals, or even other foraminifera. Parasitic strategies vary; some act as ectoparasites, using their pseudopodia to steal food from the host, while others burrow through the shell or body wall of their host to feed on its soft tissue. Foraminifera are themselves eaten by a host of larger organisms, including invertebrates, fish, shorebirds, and other foraminifera. It has been suggested, however, that in some cases predators may be more interested in the calcium from foram shells than in the organisms themselves. Several aquatic snail species are known to selectively feed upon foraminifera, often even preferring individual species. Certain benthic foraminifera have been found to be capable of surviving anoxic conditions for over 24 hours, indicating that they are capable of selective
anaerobic respiration Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain. In aerobic organisms undergoing re ...
. This is interpreted as an adaptation to survive changing oxygenic conditions near the sediment-water interface. Foraminifera are found in the deepest parts of the ocean such as the
Mariana Trench The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maximum kno ...
, including the
Challenger Deep The Challenger Deep is the deepest-known point of the seabed of Earth, with a depth of by direct measurement from deep-diving submersibles, remotely operated underwater vehicles and benthic landers, and (sometimes) slightly more by sonar ba ...
, the deepest part known. At these depths, below the
carbonate compensation depth Carbonate compensation depth (CCD) is the depth in the oceans below which the rate of supply of calcite ( calcium carbonate) lags behind the rate of solvation, such that no calcite is preserved. Shells of animals therefore dissolve and carbonate ...
, the calcium carbonate of the tests is soluble in water due to the extreme pressure. The Foraminifera found in the Challenger Deep thus have no carbonate test, but instead have one of organic material. Nonmarine foraminifera have traditionally been neglected in foram research, but recent studies show them to be substantially more diverse than previously known. They are known to inhabit disparate ecological niches, including
moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and horn ...
es, rivers, lakes and ponds, wetlands, soils,
peat bogs A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; ...
, and sand dunes.


Reproduction

The generalized foraminiferal life-cycle involves an alternation between
haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respecti ...
and
diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectiv ...
generations, although they are mostly similar in form. The haploid or gamont initially has a single
nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...
, and divides to produce numerous
gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...
s, which typically have two
flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have fro ...
. The diploid or agamont is
multinucleate Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coord ...
, and after
meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r ...
divides to produce new gamonts. Multiple rounds of
asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...
between sexual generations are not uncommon in benthic forms. Foraminifera exhibit morphological dimorphism associated with their reproductive cycle. The gamont, or sexually reproducing haploid form, is ''megalospheric''—that is, its ''proloculus'', or first chamber, is proportionally large. The gamont is also known as the ''A'' form. Gamonts, despite having typically larger proloculi, also generally have smaller overall test diameter than do agamonts. After reaching maturity, the gamont divides via
mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...
to produce thousands of gametes which are also haploid. These gametes all have a full set of
organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...
s, and are expelled from the test into the environment leaving the test undamaged. Gametes are not differentiated into
sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, wh ...
and egg, and any two gametes from a species can generally fertilize each other. When two gametes combine, they create a diploid, multi-nucleated cell known as the ''agamont,'' or ''B'' form. In contrast to the gamont, the agamont is ''microspheric'', with a proportionally small first chamber but typically larger overall diameter with more chambers. The agamont is the
asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...
phase of the foraminifera; upon reaching adulthood, the protoplasm entirely vacates the test and divides its
cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. T ...
meiotically via
multiple fission Fission, in biology, is the division of a single entity into two or more parts and the regeneration of those parts to separate entities resembling the original. The object experiencing fission is usually a cell, but the term may also refer to how ...
to form a number of haploid offspring. These offspring then begin to form their megalospheric first chamber before dispersing. In some cases the haploid young may mature into a megalospheric form which then reproduces asexually to produce another megalospheric, haploid offspring. In this case, the first megalospheric form is referred to as the ''schizont'' or ''A1'' form, while the second is referred to as the gamont or ''A2'' form. Maturation and reproduction occur more slowly in cooler and deeper water; these conditions also cause forams to grow larger. ''A'' forms always seem to be much more numerous than are ''B'' forms, likely due to the reduced likelihood of two gametes encountering one another and successfully combining.


Variations in reproductive mode

There is a high degree of diversity in reproductive strategies in different foraminiferal groups. In unilocular species, the ''A'' form and ''B'' form are still present. As in the microspheric morph of multilocular forams, the asexually reproducing ''B'' form is larger than the sexually reproducing ''A'' form. Forams in the family Spirillinidae have amoeboid gametes rather than flagellated. Other aspects of reproduction in this group are generally similar to that of other groups of forams. The calcareous spirillinid '' Patellina corrugata'' has a slightly different reproductive strategy than most other foraminifera. The asexually reproducing ''B'' form produces a cyst that surrounds the entire cell; it then divides within this cyst and the juvenile cells cannibalise the calcite of the parent's test to form the first chamber of their own test. These ''A'' forms, upon maturity, gather into groups of up to nine individuals; they then form a protective cyst around the whole group.
Gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic ...
occurs within this cyst, producing very low numbers of gametes. The ''B'' form larvae are produced inside of the cyst; any nuclei that are not bound into cells are consumed as food for the developing larvae. ''Patellina'' in ''A'' form is reportedly
dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...
, with sexes referred to as the "plus" and "minus"; these sexes differ in number of nuclei, with the "plus" form having three nuclei and the "minus" form having four nuclei. The ''B'' form is again larger than the ''A'' form.


Tests

Foraminiferal
tests 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), ...
serve to protect the organism within. Owing to their generally hard and durable construction (compared to other protists), the tests of foraminifera are a major source of scientific knowledge about the group. Openings in the test that allow the cytoplasm to extend outside are called apertures. The ''primary'' aperture, leading to the exterior, take many different shapes in different species, including but not limited to rounded, crescent-shaped, slit-shaped, hooded, radiate (star-shaped), dendritic (branching). Some foraminifera have "toothed", flanged, or lipped primary apertures. There may be only one primary aperture or multiple; when multiple are present, they may be clustered or equatorial. In addition to the primary aperture, many foraminifera have ''supplemental'' apertures. These may form as relict apertures (past primary apertures from an earlier growth stage) or as unique structures. Test shape is highly variable among different foraminifera; they may be single-chambered (unilocular) or multi-chambered (multilocular). In multilocular forms, new chambers are added as the organism grows. A wide variety of test morphologies is found in both unilocular and multilocular forms, including spiraled, serial, and milioline, among others. Many foraminifera exhibit dimorphism in their tests, with megalospheric and microspheric individuals. These names should not be taken as referring to the size of the full organism; rather, they refer to the size of the first chamber, or ''proloculus''. Tests as fossils are known from as far back as the
Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and t ...
period, and many marine sediments are composed primarily of them. For instance, the limestone that makes up the pyramids of Egypt is composed almost entirely of nummulitic benthic Foraminifera. It is estimated that reef Foraminifera generate about 43 million tons of calcium carbonate per year. Genetic studies have identified the naked amoeba ''
Reticulomyxa ''Reticulomyxa'' is a monospecific genus of freshwater foraminiferans. The type species is the unicellular ''Reticulomyxa filosa''. It is found in freshwater environments as well as moist environments, like decomposing matter and damp soils. Th ...
'' and the peculiar
xenophyophore Xenophyophorea is a clade of foraminiferans. Members of this class are multinucleate unicellular organisms found on the ocean floor throughout the world's oceans, at depths of . They are a kind of foraminiferan that extract minerals from their ...
s as foraminiferans without tests. A few other amoeboids produce reticulose pseudopods, and were formerly classified with the forams as the Granuloreticulosa, but this is no longer considered a natural group, and most are now placed among the Cercozoa.


Evolutionary history

Molecular clocks indicate that the crown-group of foraminifera likely evolved during the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is pre ...
, between 900 and 650 million years ago; this timing is consistent with Neoproterozoic fossils of the closely related filose amoebae. As fossils of foraminifera have not been found prior to the very end of the
Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and t ...
, it is likely that most of these Proterozoic forms did not have hard-shelled tests. Due to their non-mineralised tests, " allogromiids" have no fossil record. The mysterious
vendozoa Vendobionts or Vendozoans (Vendobionta) are a proposed very high-level, extinct clade of benthic organisms that made up of the majority of the organisms that were part of the Ediacaran biota. It is a hypothetical group and at the same time, it ...
ns of the Ediacaran period have been suggested to represent fossil xenophyophores. However, the discovery of diagenetically altered C27
sterol Sterol is an organic compound with formula , whose molecule is derived from that of gonane by replacement of a hydrogen atom in position 3 by a hydroxyl group. It is therefore an alcohol of gonane. More generally, any compounds that contain the gon ...
s associated with the remains of ''
Dickinsonia ''Dickinsonia'' is an extinct genus of basal animal that lived during the late Ediacaran period in what is now Australia, China, Russia and Ukraine. The individual ''Dickinsonia'' typically resembles a bilaterally symmetrical ribbed oval. Its ...
'' cast doubt on this identification and suggest it may instead be an animal. Other researchers have suggested that the elusive trace fossil '' Paleodictyon'' and its relatives may represent a fossil xenophyophore and noted the similarity of the extant xenophyophore '' Occultammina'' to the fossil; however, modern examples of ''Paleodictyon'' have not been able to clear up the issue and the trace may alternately represent a burrow or a glass sponge. Supporting this notion is the similar habitat of living xenophyophores to the inferred habitat of fossil graphoglyptids; however, the large size and regularity of many graphoglyptids as well as the apparent absence of xenophyae in their fossils casts doubt on the possibility. As of 2017 no definite xenophyophore fossils have been found. Test-bearing foraminifera have an excellent fossil record throughout the
Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anim ...
eon. The earliest known definite foraminifera appear in the fossil record towards the very end of the Ediacaran; these forms all have agglutinated tests and are unilocular. These include forms like '' Platysolenites'' and '' Spirosolenites''. Single-chambered foraminifera continued to diversity throughout the Cambrian. Some commonly encountered forms include '' Ammodiscus, Glomospira,'' '' Psammosphera,'' and '' Turritellella''; these species are all agglutinated. They make up part of the Ammodiscina, a lineage of spirillinids that still contains modern forms. Later spirillinids would evolve multilocularity and calcitic tests, with the first such forms appearing during the
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
; the group saw little effects on diversity due to the K-Pg extinction. The earliest multi-chambered foraminifera are agglutinated species, and appear in the fossil record during the middle
Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...
period. Due to their poor preservation they cannot be positively assigned to any major foram group. The earliest known calcareous-walled foraminifera are the Fusulinids, which appear in the fossil record during the Llandoverian epoch of the early
Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
. The earliest of these were microscopic, planispirally coiled, and evolute; later forms evolved a diversity of shapes including lenticular, globular, and perhaps most famously, elongated rice-shaped forms. Later species of fusulinids grew to much larger size, with some forms reaching 5 cm in length; reportedly, some specimens reach up to 14 cm in length, making them among the largest foraminifera extant or extinct. Fusulinids are the earliest lineage of foraminifera thought to have evolved symbiosis with photosynthetic organisms. Fossils of fusulinids have been found on all continents except
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
; they reached their greatest diversity during the Visean epoch of the
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonif ...
. The group then gradually declined in diversity until finally going extinct during the Permo-Triassic extinction event. During the
Tournaisian The Tournaisian is in the ICS geologic timescale the lowest stage or oldest age of the Mississippian, the oldest subsystem of the Carboniferous. The Tournaisian age lasted from Ma to Ma. It is preceded by the Famennian (the uppermost stag ...
epoch of the Carboniferous, Miliolid foraminifera first appeared in the fossil record, having diverged from the spirillinids within the Tubothalamea. Miliolids suffered about 50% casualties during both the Permo-Triassic and K-Pg extinctions but survived to the present day. Some fossil miliolids reached up to 2 cm in diameter. The earliest known Lagenid fossils appear during the Moscovian epoch of the Carboniferous. Seeing little effect due to the Permo-Triassic or K-Pg extinctions, the group diversified through time. Secondarily unilocular taxa evolved during the Jurassic and Cretaceous. The earliest Involutinid fossils appear during the Permian; the lineage diversified throughout the Mesozoic of Eurasia before apparently vanishing from the fossil record following the Cenomanian-Turonian Ocean Anoxic Event. The extant group planispirillinidae has been referred to the involutinida, but this remains the subject of debate. The
Robertinida The Robertinida are an order of Middle Triassic to recent, benthic foraminifera in which tests are planispirally to trochospirally coiled, with chambers provided with an internal partition and hyaline perforated walls composed of optically radia ...
first appear in the fossil record during the
Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...
epoch of the Triassic. The group remained at low diversity throughout its fossil history; all living representatives belong to the Robertinidae, which first appeared during the
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''palai ...
. The first definite Rotaliid fossils do not appear in the fossil record until the
Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The Pl ...
epoch of the Jurassic, following the Triassic-Jurassic event. Diversity of the group remained low until the aftermath of the Cenomanian-Turonian event, after which the group saw a rapid diversification. Of this group, the planktonic
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 ...
—the first known group of planktonic forams—first appears in the aftermath of the
Toarcian Turnover The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
; the group saw heavy losses during both the K-Pg extinction and the Eocene-Oligocene extinction, but remains extant and diverse to this day. An additional evolution of planktonic lifestyle occurred in the Miocene or Pliocene, when the rotaliid '' Neogallitellia'' independently evolved a planktonic lifestyle.


Paleontological applications

Dying planktonic Foraminifera continuously rain down on the sea floor in vast numbers, their mineralized tests preserved as fossils in the accumulating
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, san ...
. Beginning in the 1960s, and largely under the auspices of the Deep Sea Drilling, Ocean Drilling, and International Ocean Drilling Programmes, as well as for the purposes of oil exploration, advanced deep-sea drilling techniques have been bringing up sediment cores bearing Foraminifera fossils. The effectively unlimited supply of these fossil tests and the relatively high-precision age-control models available for cores has produced an exceptionally high-quality planktonic Foraminifera fossil record dating back to the mid- Jurassic, and presents an unparalleled record for scientists testing and documenting the evolutionary process. The exceptional quality of the fossil record has allowed an impressively detailed picture of species inter-relationships to be developed on the basis of fossils, in many cases subsequently validated independently through molecular genetic studies on extant specimens Because certain types of foraminifera are found only in certain environments, their fossils can be used to figure out the kind of environment under which ancient marine sediments were deposited; conditions such as salinity, depth, oxygenic conditions, and light conditions can be determined from the different habitat preferences of various species of forams. This allows workers to track changing climates and environmental conditions over time by aggregating information about the foraminifera present. In other cases, the relative proportion of planktonic to benthic foraminifera fossils found in a rock can be used as a proxy for the depth of a given locality when the rocks were being deposited. Since at least 1997, the
Paleocene–Eocene thermal maximum The Paleocene–Eocene thermal maximum (PETM), alternatively (ETM1), and formerly known as the "Initial Eocene" or "", was a time period with a more than 5–8 °C global average temperature rise across the event. This climate event o ...
(PETM) has been investigated as an analogy for understanding the
effects of global warming The effects of climate change impact the physical environment, ecosystems and human societies. The environmental effects of climate change are broad and far-reaching. They affect the water cycle, oceans, sea and land ice (glaciers), sea leve ...
and of massive carbon inputs to the ocean and atmosphere, including
ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxide ...
. Humans today emit about 10 Gt of carbon (about 37 Gt CO2e) per year, and at that rate will release a comparable amount to the PETM in about one thousand years. A main difference is that during the PETM the planet was ice-free, as the
Drake Passage The Drake Passage (referred to as Mar de Hoces Hoces Sea"in Spanish-speaking countries) is the body of water between South America's Cape Horn, Chile and the South Shetland Islands of Antarctica. It connects the southwestern part of the Atla ...
had not yet opened and the
Central American Seaway The Central American Seaway (also known as the Panamanic Seaway, Inter-American Seaway and Proto-Caribbean Seaway) was a body of water that once separated North America from South America. It formed during the Jurassic (200–154 Ma) during the b ...
had not yet closed. Although the PETM is now commonly held to be a case study for global warming and massive carbon emission, the cause, details, and overall significance of the event remain uncertain. Foraminifera have significant application in the field of
biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bi ...
. Due to their small size and hard shells, foraminifera may be preserved in great abundance and with high quality of preservation; due to their complex morphology, individual species are easily recognizable. Foraminifera species in the fossil record have limited ranges between the species' first evolution and their disappearance; stratigraphers have worked out the successive changes in foram assemblages throughout much of the
Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anim ...
. As such, the assemblage of foraminifera within a given locality can be analyzed and compared to known dates of appearance and disappearance in order to narrow down the age of the rocks. This allows paleontologists to interpret the age of
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
s when
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...
is not applicable. This application of foraminifera was discovered by Alva C. Ellisor in 1920. Calcareous fossil foraminifera are formed from elements found in the ancient seas where they lived. Thus, they are very useful in paleoclimatology and paleoceanography. They can be used, as a climate proxy, to reconstruct past climate by examining the
stable isotope The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...
ratios and trace element content of the shells (tests). Global temperature and ice volume can be revealed by the isotopes of oxygen, and the history of the
carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major component ...
and oceanic productivity by examining the stable isotope ratios of carbon; see
δ18O In geochemistry, paleoclimatology and paleoceanography ''δ''18O or delta-O-18 is a measure of the ratio of stable isotopes oxygen-18 (18O) and oxygen-16 (16O). It is commonly used as a measure of the temperature of precipitation, as a mea ...
and
δ13C In geochemistry, paleoclimatology, and paleoceanography ''δ''13C (pronounced "delta c thirteen") is an isotopic signature, a measure of the ratio of stable isotopes 13C : 12C, reported in parts per thousand (per mil, ‰). The measure is also ...
. The concentration of trace elements, like
strontium Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
(Sr),
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
(Mg),
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid e ...
(Li) and
boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
(B), also hold a wealth of information about global temperature cycles, continental weathering, and the role of the ocean in the global carbon cycle. Geographic patterns seen in the fossil records of planktonic forams are also used to reconstruct ancient
ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contou ...
s.


Modern uses

The
oil industry The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transportation (often by oil tankers and pipelines), and marketing of petroleum products. The largest ...
relies heavily on
microfossil A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...
s such as forams to find potential hydrocarbon deposits. For the same reasons they make useful biostratigraphic markers, living foraminiferal assemblages have been used as
bioindicator A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example, copepods and other sma ...
s in coastal environments, including indicators of coral reef health. Because calcium carbonate is susceptible to dissolution in acidic conditions, foraminifera may be particularly affected by changing climate and
ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxide ...
. Foraminifera have many uses in
petroleum exploration Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas, in the Earth using petroleum geology. Exploration methods V ...
and are used routinely to interpret the ages and paleoenvironments of sedimentary strata in oil wells. Agglutinated fossil foraminifera buried deeply in sedimentary basins can be used to estimate thermal maturity, which is a key factor for petroleum generation. The Foraminiferal Colouration Index (FCI) is used to quantify colour changes and estimate burial temperature. FCI data is particularly useful in the early stages of petroleum generation (about 100 °C). Foraminifera can also be used in
archaeology Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts ...
in the provenancing of some stone raw material types. Some stone types, such as
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
, are commonly found to contain fossilised foraminifera. The types and concentrations of these fossils within a sample of stone can be used to match that sample to a source known to contain the same "fossil signature".


Gallery

File:3339c Croatie Pag.jpg, Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5 mm File:3339d Croatie Pag.jpg, Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5 mm File:3339e Croatie Pag.jpg, Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5 mm File:3339f Croatie Pag.jpg, Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5 mm File:2966g Bali.jpg, Foraminifera of Indian Ocean, south-eastern coast of Bali, field width 5.5 mm File:2966j Bali.jpg, Foraminifera of Indian Ocean, south-eastern coast of Bali, field width 5.5 mm File:2966k Bali.jpg, Foraminifera of Indian Ocean, south-eastern coast of Bali, field width 5.5 mm File:Foraminifères de Ngapali.jpg, Foraminifera in Ngapali, Myanmar, field width 5.22 mm File:3579h R Indonesie.jpg, Foraminifera ''Heterostegina depressa'', field width 4.4 mm


References


External links

;General information:
The University of California Museum of Paleontology
website has a

* Researchers at the University of South Florida developed a syste

* University College London'

has an overview of Foraminifera, including many high-quality SEMs
Illustrated glossary of terms used in foraminiferal research
is the Lukas Hottinger's glossary published in the OA e-journa



Martin Langer's Micropaleontology Page

from the 2005 Urbino Summer School of Paleoclimatology ;Online flip-books:
Illustrated glossary of terms used in foraminiferal research
by Lukas Hottinger (alternative version of the one published i
"Carnets de Géologie – Notebooks on Geology"
) ;Resources:
pforams@mikrotax
– an online database detailing the taxonomy of planktonic foraminifera * Th

(part o
micro*scope
is a cooperative database of information about Foraminifera
3D models
of forams, generated by X-ray tomography
CHRONOS
ha
several Foraminifera resources
including
taxon search page
and
micro-paleo section
NB Most of this content is now included in the pforams@mikrotax website
eForams
is a web site focused on Foraminifera and modeling of foraminiferal shells
Foraminifera Gallery
Illustrated catalog of recent and fossil Foraminifera by genus and locality * {{Authority control Bikont subphyla Extant Cambrian first appearances Great Pyramid of Giza