ForaminiferaMarcelle BouDagher-Fadel

What are Foraminifera:

• with characteristic net-like pseudopodia called reticulopodia

• organic or shell-like, agglutinated or secreted outer protective layer, called a test

single-celled organisms (protists) Such organisms are classified in the Superkingdom of Protists or Protista

with a complex cell (Eukaryotes), and genetic material within a cell nucleus.

Cytoplasm is extruded as pseudopods through the aperture and any perforations

in the test

Foraminifera are placed in the “Cercozoa”.Cercozoans are amoebae with filose pseudopodia, often living within hard test

Most foraminifera grow an elaborate, solidcalcite skeleton

made of a series of chambers. The complexity of their shell structures and their evolution in time

the basis of their geological usefulness as fossils.

 Most foraminiferal tests are sand-sized (>61 mm in diameter)

Both living and fossil foraminifera• inhabited the oceans.• They are extremely abundant in

most marine sediments • in many different environments,

from live in marine to brackish habitats

• near shore to the deep sea, • and from near surface to the

ocean floor

• Some foraminifera live in oligotrophic reef associated with algae.

Composition of fossil foraminifera tests varies from

• calcareous secreted from calcium carbonate.

• agglutinated (organic compounds, sand grains and other particles cemented together, or crystalline calcite)

The test is commonly divided into chambers which are added during growth

The size of the test is associated with amount of the cytoplasm. Feeding adds to the bulk of the cytoplasm, therefore, the test has to enlarge.

Foraminifera have developed several strategies for test enlargement during ontogeny

contained growth unilocular test

The test is thought to reduce biological, physical and chemical stress

continuous growth Bilocular test

simple septate growth

multilocular

complex septate growth

Complex multiocular test

These growth patterns result in a very diverse variety of test morphologies

the simplest forms are open tubes or hollow spheres

Both living and fossil foraminifera come in a variety of shapes and sizes

Spirillina

Planispiral, evolute, undivided tube

Lagena

Undivided chamber

reticulation

a: aperture; ad: adapertural depression; li: lip; tp: toothplate with its serrated margin.

Loxostomina.

A-B: Globoturborotalites

Carpenteria

cancellation

perture terminal

Secondary aperture Main aperture

aperture

Planipiral involuteElphidium

Planipiral evoluteSpirillina

milioline

Quinqueloculina

biserial

Heterohelix

streptospiralPulleniatina

trochospiralAmmonia

Streptospiral

Planispiral Trochospiral

What are fossil foraminifera?

Fossils can be microscopic or a few centimeters long

They have inhabited the oceans for more than 500 million years and found fossilised in most type of sedimentary rocks.

Most foraminifers construct tests (shells) covering the cell body. Fossil foraminifera are the remains of their tests (shells).

Fully grown individuals range in size from about 100 micrometers to almost 20 centimeters long.

because there can be thousands of specimens in a small sediment sample.

relatively small size of tests (shells)

makes foraminifera

For, biostratigraphic, palaeo/environmental, palaeoceanographical

and palaeoclimatological reconstruction or petroleum exploration applications

much more useful than larger fossils

The study of the sequence of sedimentary rock strata is the main source for scientific knowledge about the Earth’s history, including biostratigraphy, paleogeography,

paleoclimatology and the history of life

• Orders of foraminifera (underlined include larger foraminifera (see BouDagher-Fadel, 2008). In red includes planktonic foraminifera)

• ALLOGROMIDA: organic wall, usually 1 chamber; Cambrian-Recent• ASTRORHIZIDA: agglutinated, organic cement, usually 1 chamber or branching tube; Cambrian-

Recent• LITUOLIDA: agglutinated, organic cement, many chambers, usually planispiral spiral; Cambrian-

Recent• TROCHAMMINIDA: agglutinated; organic cement, many chambers, usually trochospiral; Cambrian-

TEXTULARIIDA: agglutinated, low Mg-calcite cement; Cambrian-Recent• FUSULINIDA: microgranular calcite; many complex chambers; Silurian-Permian• MILIOLIDA: high Mg calcite, imperforate, many chambers (porcellaneous, no pores); miliolid chamber

arrangment; Carboniferous-Recent• CARTERINIDA: low Mg calcite, hyaline, pores or no pores; spicules, plani- or trochospiral; Tertiary-

Recent (?)• SPIRILLINIDA: low Mg calcite; hyaline; single crystal; spiral; Jurassic-Recent• LAGENIDA: low Mg calcite, hyaline; pores, 1 or many chambers, uniserial or planispiral; monolamellar;

Carboniferous-Recent• BULIMINIDA: low Mg calcite; hyaline; pores; many chambers; bilamellar; toothplate; Triassic?-Recent• ROTALIIDA: low Mg calcite; hyaline;  pores; many chambers; bilamellar; trocho- or planispiral,

annular, irregular; Triassic-Recent• GLOBIGERINIDA: low Mg calcite (aragonite in few extinct forms); pores; many chambers; bilamellar;

radial crystals (PLANKTON); Jurassic-Recent• INVOLUTINIDA: aragonite; 2 chambers - 2nd tube• ROBERTINIDA: aragonite; pores; many chambers; trochospiral; Triassic-Recent• SILICOLOCULINIDA:opaline silica, no pores; chamber arrangements as in miliolids; Miocene-Recent• Genetic evidence suggests strongly that Allogromida (‘naked’) and Astrorhizida (agglutinated) are one

order.

Life strategy

Float in the surface of the open oceanand sea water column

Wide distributionRapid evolution + short stratigraphic range

= excellent index fossil

Benthic foraminifera Live attached or free

At all depthmarine, brackish and freshwater habitats

sea-floor

Small Larger

Planktonic foraminifera

• Benthic foraminifera are bottom dwelling forms that can be either sessile or vagile.

Benthic foraminifera

•Vagile (mobile) foraminifera are free to move along the sea floor and/or in its substrate

Cassidulina

•Sessile foraminifera are permanently attached or fixed (not free-moving)

Ammobacculites

Miniacina

Benthic foraminifera

Small benthic foraminifera Larger benthic foraminifera

include two major groups of foraminifera

occur abundantly in the shelf regions of most tropical and subtropical shallow marine, especially in carbonate-rich,

environments

live, attached or free, at all depths, in most marine

environments, as well as in brackish, marginal marine

environment with low alkanity.

with complicated internal structureswith simple internal structures

•Benthic foraminifera are an important component of the deep-sea biomass in the present oceans, adapted to its cold, dark, and extremely oligotrophic environments.

•Larger benthic foraminifera are important shallow marine rock builders

• Faunas are highly diverse, and many species have a cosmopolitan distribution.

•In addition to their interest as indicator species living in the largest habitat on earth, their tests have been used extensively in isotope and trace element analysis aimed at reconstruction of past environments.

Larger Foraminifera with test sizes from 2mm up to 13cm are characteristic organisms inhabiting shallow water subtropical and tropical environments

today.

Alveolina

Two main factors acting as single gradients regulate the distribution of larger foraminifera within coral reef complexes.

Larger foraminifera prefer clear, nutrition depleted water as can be found in the surroundings of coral reefs.

All house symbiotic microalgae and are thus restricted to the photic zone (-130m), getting independence from food resources outside the cell.

House symbiotic algae

Allogromia has a proteinaceous test

with a single chamber.

The oldest fossil foraminifera, from the Cambrian, are simple agglutinated tubes.

Bulimina

Cibicidoides

Fusulina

rice-grain shaped tests and evolved into numerous widespread species during the Permian but large forms went extinct at the end of that period when a worldwide mass extinction also eliminated most other reef dwelling organisms.

BouDagher-Fadel, M.K., 2008. Evolution and Geological Significance of Larger Benthic Foraminifera, Developments in Palaeontology and Stratigraphy, 21, Elsevier, Amsterdam, pp 544.

Haynes, J.R., 1981. Foraminifera. MacMillan, London, pp 433.