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Fossil range: Precambrian - Recent
Live Ammonia tepida (Rotaliida)
Scientific classification
Domain: Eukaryota
Kingdom: Rhizaria
Superphylum: Retaria
Phylum: Foraminifera
d'Orbigny, 1826

Fusulinida - extinct
Involutinida - extinct
incertae sedis

The Foraminifera, ("Hole Bearers") or forams for short, are a large group of amoeboid protists with reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net.[1] They typically produce a test, or shell, which can have either one or multiple chambers, some becoming quite elaborate in structure.[2] These shells are made of calcium carbonate (CaCO3) or agglutinated sediment particles. About 275,000 species are recognized, both living and fossil. They are usually less than 1 mm in size, but some are much larger, and the largest recorded specimen reached 19 cm.

Although as yet unsupported by morphological correlates, molecular data strongly suggest that Foraminifera are closely related to the Cercozoa and Radiolaria, both of which also include amoeboids with complex shells; these three groups make up the Rhizaria.[3] However, the exact relationships of the forams to the other groups and to one another are still not entirely clear.


Living forams

Modern forams are primarily marine, although some can survive in brackish conditions.[4] A few species survive in fresh water and one even lives in damp rainforest soil. They are most commonly benthic, and about 40 morphospecies are planktonic.[1] This count may however represent only a fraction of actual diversity, since many genetically discrepant species may be morphologically indistinguishable.[5]

A number of forms have unicellular algae as endosymbionts, from diverse lineages such as the green algae, red algae, golden algae, diatoms, and dinoflagellates.[1] Some forams are kleptoplastic, retaining chloroplasts from ingested algae to conduct photosynthesis.[6]


The foraminiferal cell is divided into granular endoplasm and transparent ectoplasm from which a pseudopodial net may emerge through a single opening or through many perforations in the test. Individual pseudopods characteristically have small granules streaming in both directions.[4] The pseudopods are used for locomotion, anchoring, and in capturing food, which consists of small organisms such as diatoms or bacteria.[1]

The foraminiferal life-cycle involves an alternation between haploid and diploid generations, although they are mostly similar in form.[7][8] The haploid or gamont initially has a single nucleus, and divides to produce numerous gametes, which typically have two flagella. The diploid or schizont is multinucleate, and after meiosis fragments to produce new gamonts. Multiple rounds of asexual reproduction between sexual generations is not uncommon in benthic forms.[4]


Foraminiferan tests (ventral view)
Fossil nummulitid foraminiferans showing microspheric and megalospheric individuals; Eocene of the United Arab Emirates; scale in mm.

The form and composition of the test is the primary means by which forams are identified and classified. Most have calcareous tests, composed of calcium carbonate.[4] In other forams the test may be composed of organic material, made from small pieces of sediment cemented together (agglutinated), and in one genus of silica. Openings in the test, including those that allow cytoplasm to flow between chambers, are called apertures.

Tests are known as fossils as far back as the Cambrian period,[9] 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.[10] Production estimates indicate that reef foraminifera annually generate approximately 43 million tons of calcium carbonate and thus play an essential role in the production of reef carbonates.[11]

Genetic studies have identified the naked amoeba "Reticulomyxa" and the peculiar xenophyophores 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.[12]

Deep sea species

Foraminifera are found in the deepest parts of the ocean such as the Mariana Trench, including the Challenger Deep, the deepest part known. At these depths, below the carbonate compensation depth, 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.[13]

Four species have been found in the Challenger Deep that are unknown from any other place in the ocean, one of which is representative of an endemic genus unique to the region. They are Resigella laevis and R. bilocularis, Nodellum aculeata, and Conicotheca nigrans (the unique genus). All have tests that are mainly of transparent organic material which have small (~ 100 nm) plates that appears to be clay [13]

Evolutionary significance

Dying planktonic foraminifera continuously rain down on the sea floor in vast numbers, their mineralized tests preserved as fossils in the accumulating sediment. 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 by the millions. 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. Larger benthic foraminifera with complex shell structure react in a highly specific manner to the different benthic environments and, therefore, the composition of the assemblages and the distribution patterns of particular species reflect simultaneously bottom types and the light gradient. In the course of Earth history, larger foraminifera are replaced frequently. In particular, associations of foraminifera characterizing particular shallow water facies types are dying out and are replaced after a certain time interval by new associations with the same structure of shell morphology, emerging from a new evolutionary process of adaptation. These evolutionary processes make the larger foraminifera prone to be fossil index for the Permian, Jurassic, Cretaceous and Cenozoic (e.g. Lukas Hottinger).

Uses of forams

Because of their diversity, abundance, and complex morphology, fossil foraminiferal assemblages are useful for biostratigraphy, and can accurately give relative dates to rocks. The oil industry relies heavily on microfossils such as forams to find potential oil deposits.[14]

Calcareous fossil foraminifera are formed from elements found in the ancient seas they lived in. Thus they are very useful in paleoclimatology and paleoceanography. They can be used to reconstruct past climate by examining the stable isotope ratios of oxygen, and the history of the carbon cycle and oceanic productivity by examining the stable isotope ratios of carbon;[15] see δ18O and δ13C. Geographic patterns seen in the fossil records of planktonic forams are also used to reconstruct ancient ocean currents. Because certain types of foraminifera are found only in certain environments, they can be used to figure out the kind of environment under which ancient marine sediments were deposited.

For the same reasons they make useful biostratigraphic markers, living foraminiferal assemblages have been used as bioindicators 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.

Foraminifera can also be utilised in archaeology in the provenancing of some stone raw material types. Some stone types, such as chert, 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".


  1. ^ a b c d Hemleben, C.; Spindler, M.& Anderson, O.R. (1989). Modern Planktonic Foraminifera. Springer-Verlag. pp. 363. 
  2. ^ Kennett, J.P.; Srinivasan, M.S. (1983). Neogene Planktonic Foraminifera: A Phylogenetic Atlas. Hutchinson Ross. pp. 265. 
  3. ^ Cavalier-Smith, T. (2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 34 (4): 338–348. doi:10.1078/0932-4739-00002. 
  4. ^ a b c d Sen Gupta, B.K. (1983). Modern Foraminifera. Springer. pp. 384. 
  5. ^ Kucera, M.; Darling, K.F. (2002). "Genetic diversity among modern planktonic foraminifer species: its effect on paleoceanographic reconstructions". Philosophical Transactions of the Royal Society of London A360 (4): 695–718. 
  6. ^ Bernhard, J. M.; Bowser, S.M. (1999). "Benthic foraminifera of dysoxic sediments: chloroplast sequestration and functional morphology". Earth Science Reviews 46: 149–165. doi:10.1016/S0012-8252(99)00017-3. 
  7. ^ Moore, Lalicker, and Fischer. Invertebrate Fossils, Ch 2 Foraminifera and Radiolaria. McGraw-Hill 1952
  8. ^ Loeblich, A and Tappan H. Foraminiferida in the Treatise on Invertebrate Paleontology Part C Protista 2 Sarcodina; Geological Society of America and University of Kansas Press, 1964, fifth printing 1984
  9. ^ Sea creatures had a thing for bling - life - 08 May 2008 - New Scientist
  10. ^ Foraminifera: History of Study, University College London, retrieved 20 September 2007
  11. ^ Langer, M. R.; Silk, M. T. B., Lipps, J. H. (1997). "Global ocean carbonate and carbon dioxide production: The role of reef foraminifera". Journal of Foraminiferal Research 27 (4): 271–277. doi:10.2113/gsjfr.27.4.271. 
  12. ^ Adl, SM; Simpson, AG; Farmer, MA; Andersen, RA; Anderson, OR; Barta, JR; Bowser, SS; Brugerolle, G et al. (2005). "The new higher level classification of Eukaryotes with emphasis on the taxonomy of Protists". Journal of Eukaryotic Microbiology 52 (5): 399–451. doi:10.1111/j.1550-7408.2005.00053.x. PMID 16248873. 
  13. ^ a b New organic-walled Foraminifera (Protista) from the ocean's deepest point, the Challenger Deep (western Pacific Ocean) A. J. Gooday, Y. Todo, K. Uematsu, and H. Kitazato, Zoological Journal of the Linnean Society, 2008, 153, 399–423.
  14. ^ Boardman, R.S. (1987). Fossil Invertebrates. Blackwell. pp. 714. 
  15. ^ Zachos, J.C.; Pagani, M., Sloan, L., Thomas, E., and Billups, K. (2001). "Trends, Rhythms, and Aberrations in Global Climate, 65 Ma to Present". Science 292 (5517): 686–693. doi:10.1126/science.1059412. PMID 11326091. 

External links

General information
Online flip-Books

Illustrated glossary of terms used in foraminiferal research by Lukas Hottinger (alternative version of the one published in "Carnets de Géologie - Notebooks on Geology")

  • eForams is a web site focused on foraminifera and modeling of foraminiferal shells


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

FORAMINIFERA, in zoology, a subdivision of Protozoa, the name selected for this enormous class being that given by A. D'Orbigny in 1826 to the shells characteristic of the majority of the species. He regarded them as minute Cephalopods, whose chambers communicated by pores (foramina). Later on their true nature was discovered by F. Dujardin, working on living forms, and he referred them to his Rhizopoda, characterized by pseudopodia given off from the sarcode (protoplasm) as organs of prehension and locomotion. W. B. Carpenter in 1862 differentiated the group nearly in its present limits as " Reticularia "; and since then it has been rendered more natural by the removal of a number of simple forms (mostly freshwater) with branching but not reticulate pseudopods, to Filosa, a distinct subclass, now united with Lobosa into the restricted class of Rhizopoda.

FIG. 1A. - Lieberkiihnia, with reticulate pseudopodia.

Table of contents


Protista Sarcodina, with simple protoplasmic bodies of granular surface, emitting processes which branch and anastomose freely, either from the whole surface or from one or more elongated processes (" stylopods "); nucleus one or more (not yet demonstrated in some little known simple forms), usually in genetic relation to granules or strands of matter of similar composition, the " chromidia "scattered through the protoplasm; body naked, or provided with a permanent investment (shell or test), membranous, gelatinous, arenaceous (of compacted or cemented granules), calcareous, or very rarely (in deep sea forms) siliceous, sometimes freely perforated, but never latticed; opening by one or more permanent apertures (" pylomes ") or crevices between compacted sand-granules, often very complex; reproduction by fission (. only in simplest naked forms), or by brood formation; in the latter case one mode of brood formation (A) eventuates in amoebiform embryos, the other (B) in flagellate zoospores which are exogamous gametes, pairing but not with those of their own brood; the coupled cell (" zygote ") when mature in the shelled species gives rise to a very small primitive test-chamber or" microsphere." The adult microspheric animal gives rise to the amoebiform brood which have a larger primitive test (" megalosphere "); and megalospheric forms appear to reproduce by the A type a series of similar forms before a B brood of gametes is finally borne, to pair and reproduce the microspheric type, which is consequently rare.

The shells require special study. In the lowest forms they are membranous, sometimes encrusted with sand-grains, always very simple, the only complication being the doubling of the pylome in Diplophrys (fig. 2, 1), Shepheardella (fig. 2, 3-5), Amphitrema (fig. 2, is), Diaphorophodon (fig. 2, 12). The marine shells are, as we have seen, of cemented particles, or calcareous, glassy, and regularly perforated, or again calcareous, but porcellanous and rarely perforate. These characters have been used 1, Adult, containing two diatom 2, Adult encysted and segmented. frustules,and threeTintinnid 3, Flagellate zoospore just freed ciliates, with a large Dinofrom cyst.

flagellate just caught by the 4, Zoospore which has passed expanded reticulate pseudointo the amoeboid state. podia.

as a guide to classification; but some sandy forms have so large a proportion of calcareous cement that they might well be 'called encrusted calcareous genera, and are also not very constant in respect of the character of perforation. The porcellanous genera, however, form a compact group, the replacement of the shell by silica in forms dwelling in the red clay of the ocean abysses, where calcium carbonate is soluble, not really making any difficulty. Moreover, the shells of this group show a deflected process or neck of the embryonic chamber (" camptopyle ") at least in the megalospheric forms, whereas when such a neck exists in other groups it is straight. The opening of the shell is called the pylome. This may be a mere hole where the lateral walls of the body end, or there may be a diaphragmatic ingrowth so as to narrow the entrance. It may be a simple rounded opening, oblong or tri-multi-radiate, or branching (fig. 4, 1); or replaced by a number of coarse pores (" ethmopyle ") (fig. 3, 5a). Again, it may lie at the end of a narrowed tube (" stylopyle "), which in Lagena (fig. 3, 9) may project outwards (" ectoselenial "), or inwards (" entoselenial "). In most groups the stylopyle is straight; but in the majority of the porcellanous shells it is bent down on the side of the shell, and constitutes the " flexopyle " of A. Kemna, which being a hybrid term should be replaced by " camptopyle." The animal usually forms a simple shell only after it has attained a certain size, and this " embryonic chamber " cannot grow further. In Spirillina and Ammodiscus there is no pylomic end-wall, and the shell continues to grow as a spiral tube; in Cornuspira (fig. 3, 1) there is a slight constriction indicating the junction of a small embryonic chamber with a camptopyle, but the rest of the shell is a simple flat spiral of several turns. In the majority at least one chamber follows the first, with its own pylome at the distal end. This second chamber may rest on the first, so that the part ,on which it rests serves as a party-wall bounding the front of z, Diplophrys archeri, Barker.

a, Nucleus. Marine. The protoplasm is retracted at both ends into the tubular case.

b, Contractile vacuoles.

a, Nucleus.

c, The yellow oil-like body. 5, Shepheardella taeniiformis; Moor pools, Ireland. X 15; with pseudopodia 2, Allogromia oviformis, Duj. fully expanded.

a, The numerous nuclei; near 6-so, Varying appearance of the these the elongated bodies nucleus as it is carried along represent ingested diatoms. in the streaming protoplasm Freshwater. Figs. 2, 3, I I, within the tube.

12 belong to Rhizopoda 11, Amphitrema wrightianum, Filosa, and are included Archer, showing membranous here to show the character shell encrusted with foreign istic filose pseudopodia in particles. Moor pools, Irecontrast with the reticulate land.

spread of the others. 12, Diaphorophodon mobile, 3, Shepheardella taeniiformis, Archer. [land.

Siddall (Quart. Jour. Micr. a, Nucleus. Moor pools, Ire- Sci., 1880); X 30 diameters.

the newer chamber as well as the back of the older; and this state prevails for all added chambers in such cases. In the 4 FIG. Is. - Protomyxa aurantiaca, Haeck. (After Haeckel.) 10 A 7 8 FIG. 2. - Allogromiidea. highest vitreous shells, however, each chamber has its complete " proper wall "; while a " supplementary skeleton," a deposit of shelly matter, binds the chambers together into a compact whole. In all cases the protoplasm from the pylome may deposit additional matter on the outside of the shell, so as to produce very characteristic sculpturing of the surface.

Compound or " polythalamic " shells derive their general form largely from the relations of successive chambers in size, shape and direction. This is well shown in the porcellanous Miliolidae. If we call the straight line uniting the two ends of a chamber the " polar axis," we find that successive chambers FIG. 3.-Various forms of Calcareous Foraminifera.

1, Cornuspira. 8, Orbiculina (spiral). 14, Textularia. 2, Spiroloculina. 9, Lagena. 15, Discorbina. 3, Triloculina. 10, Nodosaria. 16, Polystomella. 4, Biloculina. 11, Cristellaria. 17, Planorbulina. 5, Peneroplis. 12, Globigerina. 18, Rotalia. 6, Orbiculina (cyclical). 13, Polymorphina. 19, Nonionina. 7, Orbiculina (young).

have their pylomes at alternate poles; but they lie on different meridians. In Spiroloculina (fig. 3, 2) the divergence between the meridians is 180°, and the chambers are strongly incurved, so that the whole shell forms a flat spiral, of nearly circular outline. In the majority, however, the chambers are crescentic in section, their transverse prolongations being termed " alary " outgrowths, so that successive chambers overlap; when under this condition the angle of successive meridians is still 180° we have the form Biloculina (fig. 3, 4), or with the alary extensions completely enveloping, Uniloculina; when the angle is 120° we have Triloculina, or 144°, Quinqueloculina. Again in Peneroplis (figs. 3, 5, and 4) the shell begins as a flattened shell which tends to straighten out with further growth and additional chambers. In some forms (Spirolina, fig. 22, 3) the chambers have a nearly circular transverse section, and the adult shell is thus crozier-shaped. In others (which may have the same sculpture, and are scarcely distinguishable as species) the chambers are short and wide, drawn out at right angles to the axis, but in the plane of the spiral, and the growing shell becomes fanshaped or " flabelliform " (figs. 3, 5, 4, 2). This widening may go on till the outer chambers form the greater part of a circle, as in Orbiculina (fig. 3, 6-8) where, moreover, each large chamber is subdivided by incomplete vertical bulkheads into a tier of chamberlets; each chamberlet has a distinct pylomic pore opening to the outside or to those of the next outer zone. In Orbitolites (figs. 5, 6) we have a centre on a somewhat Milioline type; and after a few chambers in spiral ?II"r'?_?i?r?' ?a? f i t  ? ? 1 j?. js;1 ' 'o??'/?11?????j?1? ' '., "....;1070 , I ' .IJ ??y.rJ..?° FIG. 5.-Shell of simple type of Orbitolites, showing primordial chamber a, and circumambient chamber b, surrounded by successive rings of chamberlets connected by circular galleries which open at the margin by pores.

succession, complete circles of chambers are formed. In the larger forms the new zones are of greater height, and horizontal bulkheads divide the chamberlets into vertical tiers, each with its own pylomic pore.

The Cheilostomellidae (fig. 3,13) reproduce among perforate vitreous genera what we have already seen in the Miliolida: Orbitoides (fig. 10,2) and Cycloclypeus, among the Nummulite group, with a very finely perforate wall, recall the porcellanous Orbiculina and Orbitolites. In flat spiral forms (figs. 22, 1, 7; 3, 2, 16, 19, &c.) all successive chambers I 2 FIG. 4.-Modifications of Peneroplis. 1, Dendritina; 2, Eu-Peneroplis. FIG. 6.-Animal of simple type of Orbitolites, showing primordial segment a, and circumambient segment b, surrounded by annuli of sub-segments connected by radial and circular stolon-processes.

the chambers may be freely exposed; or the be wider transversely than their predecessors ' becoming " nautiloid "; in extreme cases only the last turn or whorl is seen (fig. II). When the spiral axis is conical the shell may be " rotaloid," the larger lower chambers partially concealing the upper smaller ones (fig. 3, 12, 15, or they may leave, as in Patellina, a wide central conical cavity - which, in this genus, is finally occupied by later formed " supplementary" chambers. When the successive chambers are disposed around a longitudinal cent r a l axis they may be said plant. If the arrangement a FIG. 7. - Section of Rotalia showing the canal system, a, b, substance of the intermediate d, tubulated chamber-wall.

a, Retral processes, proceeding from the posterior margin of one of the segments. d,

b, b', Smooth anterior margin of the same segment. e,

c, c', Stolons connecting succes- sive segments and uniting f, themselves with the di-

verging branches of the meridional canals.

d', d 2, Three turns of one of the spiral canals.

e 1, 2 Three of the meridional canals.

f 1, f 2 , Their diverging branches.

to " alternate " like the leaves of a beccarii, c, in the skeleton; FIG. 8. - Internal cast of Polystomella craticulata. is distichous we get such forms as Polymerphina, Textularia and Frondicularia (fig. 3, 13, 14), if tristichous, Tritaxia. Such FIG. 9. - Operculina laid open, to show its internal structure.

a, Marginal cord seen in cross interseptal canals, the section at a'. [chambers. general distribution of b, b, External walls of the which is seen in the septa c, c, Cavities of the chambers. e, e; the lines radiating c', c', Their alar prolongations. from e, e point to the d, d, Septa divided at d', d', and secondary pores.

at d", so as to lay open the g, g, Non-tubular columns.

an arrangement may coexist with a spiral twist of the axis for at least part of its course, as in the crozier-shaped Spiroplecta. Two phenomena interfere with the ready availability of the characters of form for classificatory ends - dimorphism and multiformity.


The majority of foraminiferal shells show two types, the rarer with a much smaller central chamber than that of the more frequent. The chambers are called microsphere 2 wcs ss FIG. to.-1, Piece of Nummulitic Limestone from the Pyrenees, showing Nummulites laid open by fracture through the median plane; 2, vertical section of Nummulite; 3, Orbitoides. and megalosphere, the forms in which they occur microsphaeric and megalosphaeric forms, respectively. We shall study below their relation to the reproductive cycle.


Many of the Polythalamia show different types of chamber-succession at different ages. We have noted FIG. I I. - Vertical section of portion of Nummulites, showing the investment of the earlier whorls by the alar prolongations of the later.

a, Marginal cord.

b, Chamber of outer whorl.

c, c, Whorl invested by a. d, One of the chambers of the fourth whorl from the margin. [closed whorls.

e, e', Marginal portions of the en n this phenomenon in such crozier forms as Peneroplis, as well as in discoid forms; it is very frequent. Thus the microspheric Biloculina form the first few chambers in quinqueloculine succession. The microspheric forms attain to a greater size when adult than the megalospheric; and in Orbitolites the microsphere has a straight, Q outlet, orthostyle, instead of the deflected camptostyle one, so general in porcellanous t y p e s; and the spiral succession is continued for more turns before reaching the fan-shape d and finally cyclic stage. Globigerina, whose chambers are nearly spherical, is sometimes seen to be enclosed in a spherical test, perforate, but without a pylome, and known as Orbulina; the chambered Globigerina-shell is attached at first inside the wall of the Orbulina, but ultimately disappears. The ultimate fate of the Orbulina shell is unknown; but it obviously marks a turning-point in the life-cycle.

Protoplasmic Body and Reproduction

The protoplasm is not differentiated into ectoand endosarc, although it is often denser f, Investing portion of the outer whorl.

g, g, Spaces left between the investing portions of successive whorls.

h, h, Sections of the partitions dividing these.

FIG. 12. - Internal surface of wall of two chambers, a, a, of Nummulites, showing the orifices of its minute tubuli.

b, b, The septa containing canals.

c, c, Extensions of these canals in the intermediate skeleton.

d, d, Larger pores.

in the central part within the shell, and clearer in the pseudopodial ramifications and the layer (or stalk in the monothalamic forms) from which it is given off. In pelagic forms like Globigerina the external layer is almost if not quite identical in structure with the extracapsular protoplasm of Radiolaria, being differentiated into granular strands traversing a clear jelly, rich in large vacuoles (alveoli), and uniting outside the jelly to form the basal layer of the pseudopods; these again are radiolarian in character. Hence E. R. Lankester justly enough compares the shell here to the central capsule of the Radiolarian, though the comparison must not be pushed too far. The cyto ? ?,? plasm contains granules of 6 o Q on ° ^ ? o?oo og?a0000 0 various kinds, and the in ? o o ° ooh = ..° ? ternal protoplasm is some ?- times pigmented. The Chrysomonad Flagellate, Zooxanthella, so abundant in its resting state - the so-called " yellow cells " - in the extracapsular protoplasm of Radiolaria (q.v.) also occurs in the outer protoplasm of many Foraminifera, not only pelagic but also bottomdwellers, such as Orbitolites. The nucleus is single in the Nuda and Allogromidia and in the megalospheric forms of higher Foraminifera; but microspheric forms when adult contain many simple similar nuclei. The nucleus in every case gives off granules and irregular masses (" chromidia ") of similar reactions, which play an important part in reproduction. During the maturation of the microsphere the nuclei disappear; and the cytoplasm breaks up into a large number of zoospores, each of which is soon provided with a single nucleus, whether entirely derived from the parent-nucleus or from the coalescence of chromidia, or from both these sources is still uncertain. These zoospores are amoeboid; they soon secrete a shell and reveal themselves as megalospheres, the original state of the megalospheric forms. In the adult megalosphere the solitary nucleus disappears and is replaced by hosts of minute vesicular nuclei, formed by the concentration of chromidia. Each nucleus aggregates around it a proper zone of dense protoplasm; by two successive mitotic divisions each mass becomes quadri-nucleate, and splits up into four biflagellate, uninucleate zoospores. These are pairing-cells or gametes, though they will not pair with members of the same brood. In the zygote resulting from pairing two nuclei soon fuse into one; but this again divides into two; an embryonic shell is secreted, and this is the microspheric type, which is multinuclear from the first. F. Schaudinn compares the nuclei of the adult Foraminifera with the (vegetative) meganucleus of Infusora (q.v.) and the chromidial mass with the micronucleus, whose chief function is reproductive.

Since megalospheric forms are by far the most abundant, it seems probable that under most conditions they also give rise to megalospheric young like themselves; and that the production of zoospores, FIG. 14. - Vertical section of tubulated chamber-walls, a, a, of Nummulites. b, b, Marginal cord; c, cavity of chamber; d, d, nontubulated columns.

pairing to pass into the microspheric form, is only occasional, and possibly seasonal. This life-history we owe to the researches of Schaudinn and J. J. Lister.

In several species (notably Patellina) plastogamy, the union of the cytoplasmic bodies without nuclear fusion, has been noted, as a prelude to the resolution of the conjoined protoplasm into uninucleate amoebulae.

Calcituba, a porcellanous type, which after forming the embryonic chamber with its deflected pylome grows into branching stems, may fall apart into sections, or the protoplasm may escape and break up into small amoebulae. Of the reproduction of the simplest forms we know little. In Mikrogromia the cell undergoes fission within the test, and on its completion the daughter-cells may emerge as brflagellate zoospores.

The sandy shells are a very interesting series. In Astrorhiza the sand grains are loosely agglutinated, without mineral cement;. they leave numerous pores for the exit of the protoplasm, and there are no true pylomes. In other forms the union of the grains by a calcareous or ferruginous cement necessitates the existence of distinct pylomes. Many of the species reproduce the varieties of form found in calcareous tests; some are finely perforated, others not. Many of the larger ones have their walls thickened internally and traversed by complex passages; this structure is called laby FIG. I 5. - Cycloclypeus. rinthic (fig. 19, g, h). The shell of Endothyra, a form only known to. us by its abundance in Carboniferous and Triassic strata, is largely composed of calcite and is sometimes perforated.

It is noteworthy that though of similar habitat each species selects its own size or sort of sand, some utilizing the siliceous spicules of sponges. Despite the roughness of the materials, they are often so laid as to yield a perfectly smooth inner wall; and sometimes. the outer wall may be as simple. As we can find no record of a deflected stylopyle to the primitive chamber of the polythalamous. Arenacea, it is safe to conclude that they have no close alliance with the Porcellanea.

Classification. I. NuDA. - Protoplasmic body without any pellicle or shell save in the resting encysted condition, sometimes forming colonial aggregates by coalescence of pseudopods (Myxodictyum), or even plasmodia (Protomyxa). Brood-cells at first uniflagellate or amoeboid from birth. Fresh-water and marine genera Protogenes (Haeckel), Biomyxa (Leidy), Myxodictyum (Haeckel), Protomyxa (Haeckel) (fig. Is).

This group of very simple forms includes many of Haeckel's Monera, defined as " cytodes," masses of protoplasm without a nucleus. A nucleus (or nuclei) has, however, been demonstrated by improved methods of staining in so many that it is probable that this distinction will fall to the ground.

II. Allog Romidiaceae (figs. I A, 2). - Protoplasmic body protected in adult state by an imperforate test with one or two openings (pylomes) for the exit of the stylopod; test simple, gelatinous, membranous, sometimes incrusted with foreign bodies, never calcareous nor arenaceous; reproduction by fission alone known. Freshwater or marine genera Allogromia (Rhumbl.), Myxotheca (Schaud.), Lieberkiihnia (Cl. & L.) (fig. IA), Shepheardella (Siddall) (fig. 2, 3 - Diplophrys (Barker), Amphitrema (Arch.) (fig. 2, r 1), Diaphorophodon (Arch.) (fig. 2, 12), are possibly Filosa. This group differs from the preceding in its simple test, but,. like it, includes many fresh-water species, which possess contractile vacuoles.

III. Astrorhizidiaceae. - Simple forms, rarely polythalamous (some Rhabdamminidae), but often branching or radiate; test arenaceous, loosely compacted and traversed by chinks for pseudopodia (Astrorhizidae), or dense, and opening by one or more terminal pylomes at ends of branches. Marine, 4 Fam. The test of some Astrorhizidae is so loose that it falls to pieces when taken out of water. Haliphysema is. remarkable for its history in relation to the " gastraea theory." Pilulina has a neat globular shell of spongespicules and fine sand. Genera, Astrorhiza (Sandahl).

a 011?? i Tm i b b b FIG. 13. - Internal cast of two chambers, a, a, of Nummulites, the radial canals between them passing into b, marginal plexus.


16. - Heterostegina.

Lagenidaceae.-Shells vitreous, often sculptured, monoor polythalamic, finely perforate; chambers flask-shaped, with a protruding or an inturned stylopyle; Lagena (Walker & Boys) (fig. 4, 9); Nodosaria (Lamk.) (figs. 23, 4; 4, 10); Polymorphina (d'Orb.) (fig. 4, 13); Cristellaria (Lamk.) (fig. 4, //); Frondicularia (Def.) (fig. 2 3, 3).

Globigerinidaceae.-Shells vitreous, coarsely perforated; chambers few spheroidal rapidly increasing in size; arranged in a trochoid or nautiloid spiral. Globigerina (Lamk.) (23, 6; 4, 12); Hastigerina (Wyville Thompson) (fig. 23, 5); Orbulina (d'Orb.) (fig. 23, 8). X. Rotalidaceae.-Shells vitreous, finely perforate; walls thick, often double, but without an intermediate partylayer traversed by canals; form usually spiral or trochoid. Discorbina (Parker & Jones) (fig. 4, 15); Planorbulina (d'Orb.) (fig. 4, 17); Rotalia (Lamk.) (figs. 23, 1, 2; 7, 21); Calcarina (d'Orb.) (fig. 23, 10); Polytrema (Risso) (fig. 23, 9). (fig. 22), Pilulina (Carptr.) (fig. 19), Saccammina (Sars) (fig. 19), Rhabdammina (Sars), Botellina (Carptr.), Haliphysema (Bowerbank) (fig. 22).

IV. LITu0LIDACEAE.-Shell arenaceous, usually fine-grained, definite and often polythalamic, recalling in structure calcareous forms. Lituola (Lamk.) (fig. 19), Endothyra (Phil.), Ammodiscus (Reuss), Loftusia (Brady), Haplophragmium (Reuss) (fig. 22), Thurammina (Brady) (fig. 22).

V. Miliolidaceae.-Shells porcellanous imperforate, almost invariably with a camptostyle leading from the embryonic chamber; Cornuspira (Schultze) (fig. 3); Miliola (Lamk.), including as subgenera Spiroloculina (d'Orb.) (figs. 3 and 22); Triloculina (d'Orb.) (fig. 3); Biloculina (d'Orb.) (fig. 3); Uniloculina (d'Orb.); Quinqueloculina (d'Orb.); Peneroplis (Montfort) (figs. 22, 3; 3), with form Dendritina (fig. 4, I); Orbiculina (Lamk.) (fig. 3, 6-8); Orbitolites (Lamk.) (figs. 5, 6); Vertebralina (d'Orb.) (fig. 22); Squamulina (Sch.) (fig. 22); Calcituba (Schaudinn).

VI. Textulariadaceae.-Shells perforate, vitreous or (in the larger forms) arenaceous, in two or three alternating ranks (distichous or tristichous). Textularia (Defrance) (fig. 21).

VII. Cheilostomellaceae.-Shells vitreous, thin, the chambers doubling forwards and backwards as in Miliolidae. Cheilostomella (Reuss).

a b FIG. 18.-Biloculina depressa d'Orb., transverse sections showing dimorphism. (From Lister.) a, Megalospheric shell X 50, showing uniform growth, biloculine throughout.

b, Microspheric shell X 90, showing multiform growth, quinqueloculine at first, and then multiform.

XI. Nummulinidaceae.-As in Rotalidaceae, but with a thicker finely perforated shell, often well developed, and a supplementary skeleton traversed by branching canals as an additional party-wall between the proper chamber-walls. Nonionina (d'Orb.) (fig. 4, 19); Fusulina (Fischer) (fig. 20); Polystomella into (Lamk.) (figs. 4, 16; 8); Operculina (d'Orb.) (fig. 9); Heterostegina (d'Orb.) (fig. 16); Cycloclypeus (Carptr.) (fig. 15); Nummulites (Lamk.) (figs. 10, II, 12, 1 3, 14) "Eozoon canadense," described as a species of this order by J. W. Dawson and Carpenter, has been pronounced by a series of enquirers, most of whom started with a belief in its organic structure, to be merely a complex mineral concretion in ophicalcite, a rock composed of an admixture of silicates (mostly serpentine and pyroxene) and calcite.

Distribution Vertical Space.-Owing to their lack of organs for active locomotion the Foraminifera are all crawling or attached, with the exception of a few genera (very rich in species, however) which float near the surface. of the ocean, constituting part of the pelagic plankton. Thus the majority are littoral or deep-sea, sometimes attached to other bodies or even burrowing in the tests of other Foraminifera; most of the fresh-water forms are sapropelic, inhabiting the layer of organic Young megalospheric individual. Adult decalcified.

Later stage, resolving itself into two flagellate gametes.

Conjugation. [zygote. Microspheric individual produced from The same resolved itself into pseudo 1, Modified from F. Schaudinn, in Lang's Zoologie. FIG. 17.-Life Cycle of Polystomella crispa. podiospores which are growing new megalospheric individuals. Principal nucleus, and 2, . subsidiary nuclei of megalospheric form.


Nuclei in multiple division. Chromidia derived from 4.

debris at the surface of the bottom mud ditches of pools, ponds and lakes. The deep-sea species below a certain depth cannot possess a calcareous shell, for this would be dissolved; and it is in these that we find limesalts sometimes replaced by silica.

The pelagic floating genera are also specially modified. Their shell is either thin or extended many times by long slender tapering spines, and the protoplasm outside has the same character as that of the Radiolaria (q.v.), being differentiated into jelly containing enormous vacuoles and traversed by reticulate strands of granular protoplasm. These coalesce into a peripheral zone from which protrude the pseudo FIG. 19. - Arenaceous Foraminifera.

a, Exterior of Saccammina. f, Nautiloid Lituola, exterior.

b, The same laid open. g, Chambered interior.

c, Portion of test more highly h, Portion of labyrinthic chammagnified. ber wall, showing component d, Pilulina. [magnified. sand-grains.

e, Portion of test more highly pods, here rather radiate than reticulate. Most genera and most species are cosmopolitan; but local differences are often marked. Foraminifera abound in the shore sands and the crevices of coral reefs. The membranous shelled forms decay without leaving traces. The sandy or calcareous shells of dead Foraminifera constitute a large proportion of littoral sand, both below and above tide marks; and, as shown in the boring on Funafuti, enter largely into the constituents of coral rock. They may accumulate in the mud of the bottom to constitute Foraminiferal ooze. The source of these shells in the latter case is double: (I) shells of bottom-dwellers accumulate on the spot; (2) shells of dead plankton forms sink down in a continuous shower, to form a layer at the bottom of the ocean, during which process the spines are dissolved by the sea-water. Thus is formed an ooze known as " Globigerina-ooze," being formed largely of that genus and its ally Hastigerina; below 3000 fathoms even the tests themselves are dissolved. Casts of their bodies in glauconite (a green ferrous silicate, whose composition has not yet been accurately determined) are, however, frequently left. Glauconitic casts of perforate shells, notably Globigerina, have been found in Lower Cambrian (e.g. Hollybush Sandstone), and the shells themselves in Siberian limestones of that age. It is only when we pass into the Silurian Wenlock limestone that sandy shells make their appearance. Above this horizon Foraminifera are more abundant as constituents, partial or principal of calcareous rocks, the genus Endothyra being indeed almost confined to Carboniferous beds. The genus Fusulina (fig. 20) and Saccammina (fig. 19) give their names (from their .FIG. 20. - Section of Fusulina Limestone.

respective abundance) to two limestones of the Carboniferous series. Porcellanous shells become abundant only from the Lias upwards. The glauconitic grains of the Greensand formations are chiefly foraminiferal casts. Chalk is well known to consist largely of foraminiferal shells, mostly vitreous, like the north Atlantic globigerina ooze. In the Maestricht chalk more littoral conditions prevailed, and we find such large-sized FIG. 2 i. - Microscopic Organisms in Chalk from Gravesend. a, b, c, d, Textularia globulosa; e, e, e, e, Rotalia aspera; f, Textularia aculeata; g, Planularia hexas; h, Navicula. species as Orbitoides (vitreous) and Orbitolites (porcellanous; figs. 5, 6), &c. In the Eocene Tertiaries the Calcaire Grossier of the Paris basin is mainly composed of Miliolid forms. Nummulites occur in English beds and in the Paris basin; but the great beds of these, forming reef-like masses of limestone, occur farther south, extending from the Pyrenees through the southern and eastern Alps to Egypt, Sinai, and on to north India. The peculiar structure occurring in the Lower Laurentian limestone, as well as other limestones of Archean age described as a Nummulitaceous genus, " Eozoon," by Carpenter and Dawson, and abundantly illustrated in the 9th edition of his encyclopaedia, is now universally regarded as of inorganic origin. " Looking P ,?

": i, Spiroloculina planulata, Lamarck, showing five "coils"; porcellanous.

2, Young ditto, with shell dissolved and protoplasm stained so as to show the seven nuclei n. 3, Spirolina (Peneroplis); a sculptured imperfectly coiled shell; porcellanous.

4, Vertebralina, a simple shell consisting of chambers succeeding one another in a straight line; porcellanous.

5, 6, Thurammina papillate, Brady, a sandy form. 5 is broken open so as to show an inner chamber; recent. X 25.

7, Haplophragmium canariensis, a sandy form; recent.

8, Nucleated reproductive bodies (bud-spores) of Haliphysema. 9, Squamulina laevis, M. Schultze; X 40; a simple porcellanous Miliolide.

lo, Protoplasmic core removed after treatment with weak chromic acid from the shell of Haliphysema tumanovitzii, Bow. n, Vesicular nuclei, stained with haematoxylin. (After Lankester.) rr, Haliphysema tumanovitzii; X 25 diam.; living specimen, showing the wineglass-shaped shell built up of sand-grains and sponge-spicules, and the abundant protoplasm p, issuing from the mouth of the shell and spreading partly over its projecting constituents.

12, Shell of Astrorhiza limicola, Sand.; X i; showing the branching of the test on some of the rays usually broken away in preserved specimens (original).

13, Section of the shell of Marsipella, showing thick walls built of sand-grains.

FIG. 23. - Perforata.

z, Spiral arrangement of simple chambers of a Reticularian shell, as in small Rotalia. 2, Ditto, with double septal walls, and supplemental shell-substance (shaded), as in large Rotalie. 3, Diagram to show the mode in which successively-formed chambers may completely embrace their predecessors, as in Frondicularia. 4, Diagram of a simple straight series of non-embracing chambers, as in Nodosaria. 5, Hastigerina murrayi, Wyv. Thomson. a. Bubbly (vacuolated) protoplasm, enclosing b, the perforated Globigerina-like shell (conf. central capsule of Radiolaria). From the peripheral protoplasm project, not only fine pseudopodia, but hollow spines of calcareous matter, which are set on the shell, and have an axis of active protoplasm. Pelagic; drawn in the living state.

6, Globigerina bulloides, d'Orb., showing the punctiform perforations of the shell and the main aperture.

7, Fragment of the shell of Globigerina, seen from within, and highly magnified. a, Fine perforations in the inner shell substances; b, outer (secondary) shell substance. Two coarser perforations are seen in section, and one lying among the smaller.

8, Orbulina universe, d'Orb. Pelagic example, with adherent radiating calcareous spines (hollow), and internally a small Globigerina shell. It is probably a developmental phase of Globigerina. a, Orbulina shell; b, Globigerina shell.

9, Polytrema miniaceum, Lin.; X 12. Mediterranean. Example of a branched adherent calcareous perforate Recticularian.

zo, Cakarina spengleri, Gmel.; X io. Tertiary, Sicily. Shell dissected so as to show the spiral arrangement of the chambers, and the copious secondary shell substance. a 2, a 3, 'a' 4, Chambers of three successive coils in section, showing the thin primary wall (finely tubulate) of each; b, b, b, b, perforate surfaces of the primary wall of four tiers of chambers, from which the secondary shell substance has been cleared away; c', c', secondary or intermediate shell substance in section, showing coarse canals; d, section of secondary shell substance at right angles to c'; e, tubercles of secondary shell substance on the surface; f, f, club-like processes of secondary shell substance.

at the almost universal diffusion of existing Foraminifera and the continuous accumulation of their shells over vast areas of the ocean-bottom, they are certainly doing more than any other group of organisms to separate carbonate of lime from its solution in sea-water, so as to restore to the solid crust of the earth what is being continuously withdrawn from it by solution of the calcareous materials of the land above sea-level." (E. R. Lankester, " Protozoa," Ency. Brit. 9th ed.) Historical. - The Foraminifera were discovered as we have seen by A. d'Orbigny. C. E. Ehrenberg added a large number of species, but it was to F. Dujardin in 1835 that we owe the recognition of their true zoological position and the characters of the living animal. W. B. Carpenter and W. C. Williamson in England contributed largely to the study of the shell, the latter being the first to call attention to its multiform character in the development of a single species, and to utilize the method of thin sections, which has proved so fertile in results. W. K. Parker and H. B. Brady, separately, and in collaboration, described an enormous number of forms in a series of papers, as well as in the monograph by the latter of the Foraminifera of the " Challenger " expedition. Munier-Chalmas and Schlumberger brought out the fact of dimorphism in the group, which was later elucidated and incorporated in the full cytological study of the life-cycle of Foraminifera by J. J. Lister and F.

Schaudinn, independently, but with concurrent results.

Literature. - The chief recent books are: F. Chapman, The Foraminifera (1902), and J. J. Lister, " The Foraminifera," in E. R. Lankester's Treatise on Zoology (1903), in which full bibliographies will be found. For a final resume of the long controversy on Eozoon, see George P. Merrill in Report of the U.S. National Museum (1906), p. 635. Other classifications of the Foraminifera will be found by G. H. Theodor Eimer and C. Fickert in Zeitschr. fur wissenschaftliche Zoologie, lxv. (1899), p. 599, and L. Rhumbler in Archiv fir Protistenkunde, iii. (1903-1904); the account of the reproduction is based on the researches of J. J. Lister, summarized in the above-cited work, and of F. Schaudinn, in Arbeiten des kaiserlichen Gesundheitsamts, xix. (1903). We must also cite W. B. Carpenter, W. K. Parker and T. Rymer Jones, Introduction to the Study of the Foraminifera (Ray Society) (1862); W. B. Carpenter, " Foraminifera," in Ency. Brit., 9th ed.; W. C. Williamson, On the Recent Foraminifera of Great Britain (Ray Society), (1858); H. B. Brady, " The Foraminifera," in Challenger Reports, ix. (1884); A. Kemna, in Ann. de la soc. royale zoologique et malacologique de Belgique, xxxvii. (5902), p. 60; xxxix. (1904), p. 7.


The Xenophyophoridae are a small group of bottomdwelling Sarcodina which show a certain resemblance to arenaceous Foraminifera, though observations in the living state show that the character of the pseudopodia is lacking. The multinucleate protoplasm is contained in branching tubes, aggregated into masses of definite form, bounded by a common wall of foreign bodies (sponge spicules, &c.) cemented into a membrane. The cytoplasm contains granules of BaSO 4 and pellets of faecal matter. All that is known of reproduction is the resolution of the pellets into uninucleate cells.

(F. E. Schultze, Wissenschaftliche Ergebnisse der deutschen TiefseeExpedition, vol. xi., 5905, pt. i.) (M. HA.)

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Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary




Proper noun


  1. (taxonomy) A taxonomic subphylum within the phylum Retaria — the foraminifers.


See also


Up to date as of January 23, 2010

From Wikispecies


Main Page
Cladus: Eukaryota
Supergroup: Rhizaria
Phylum: Retaria
Subphylum: Foraminifera
Classes: Athalamea - Polythalamea - Xenophyophorea - Schizocladea

[See also Monothalamea]


  • Longet, D.; Pawlowski, J. 2007: Higher-level phylogeny of Foraminifera inferred from the RNA polymerase II (RPB1) gene. European journal of protistology, 43: 171-177.
  • Pawlowski, J.; Holzmann, M. 2002: Molecular phylogeny of Foraminifera - a review. European journal of protistology, 38: 1-10.

Vernacular names

Türkçe: Delikliler

Simple English

File:Planktic Forams Late
A group of foram tests from the Pliocene.
A living foram

Foraminifera or forams, as they are called, are an important group of tiny single-celled eukaryotes. They are mostly marine, though a few live in fresh-water, and even on damp land areas. In the sea, they live both in the plankton (pelagic), and in the deeper water (the benthos). They have tests (like shells) made of calcium carbonate (CaCO3).[1]

The organism has pseudopodia like an amoeba. It uses these to capture and eat bacteria and small diatoms. Also, many of them keep algal endosymbionts. Some are idioplastic, which means they eat the algae, but keep the algal chloroplasts for their own benefit.

Forams are often used to date strata in palaeontology. The detailed record of forams from deep sea drilling projects are the basis of a fossil index for geological periods or stages. This is called biostratigraphy.

Deep sea forams from the Mariana Trench are below the carbonate compensation depth, below which all CaCO3 dissolves. They have evolved organic tests, instead of calcium carbonate ones.[2] This suggests that the tests are a vital part of their life-style, perhaps protecting them from other micro-predators.


  1. Hemleben C. Spindler M. & Anderson O.R. 1989. Modern planktonic Foraminifera. Springer-Verlag, Berlin.
  2. Gooday A.J. Todo Y. Uematsu K. and Kitazato H. 2008. New organic-walled Foraminifera (Protista) from the ocean's deepest point, the Challenger Deep (western Pacific Ocean). Zoological Journal of the Linnean Society. 153, 399–423.


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