by Brian Darnton, UK
(A downloadable and printable version of this article in Word for Windows 'doc' format is here.)
The following is a guide to the position of Foraminifera in the animal world.
Class-------Sarcodina (Amoeboid creatures)
Sub-Class- Rhizopoda (Without Skeleton)
Order-------Foraminifera (Cell processes usually form a network. Single or many chambered test.)
Foraminifera are essentially unicellular animals which have an ability to grow a protective test. Although they are simple creatures they can exhibit a fairly complex lifestyle including an alternation of generations with haploid and diploid forms existing. In practical terms an examination of the proloculum or first chamber will reveal whether the test was produced from asexual budding when it is larger than the subsequent chambers or from a sexually produced gamete when it is much smaller than the subsequent chambers. The Foraminifera may be benthic but some species are mainly planktonic in nature.
HISTORY OF THE LITERATURE OF THE FORAMINIFERA.
There is some evidence that Pliny the elder was one of the first to discover Forams in a layer of fossils which he called a plaster layer in the rocks of Sicily (Ref. 1) though it was Dr. Ulisse Aldrovandi the Italian scientist and medical man who was the first to document and illustrate one of them in his MUSEUM METALLICUM of 1648.
Robert Hooke (1635-1703) was certainly one of the first to publish work on the Forams in English in his MICROGRAPHICA of 1665 (Ref. 2). On page 44 Scheme 5 fig 10. of the Dover version there is a small representation of a Foram which seems to be something like Ammonia beccarii.
Anthony van Leeuwenhoek (1632-1723) also made reference to the group in his letters to the Royal Society at a similar period of time. One of his drawings of an Elphidium crispum found at Scheveningen can be found reproduced in his biography by C. Dobel (Ref. 3) in ANTONY VAN LEEUWENHOEK AND HIS LITTLE ANIMALS.
None of these works were of any magnitude from the point of view of the Foraminifera and it was not until Carl Linnaeus wrote his SYSTEMA NATURAE 10th ed. during 1758-1759 (Ref. 4) that 15 different species were listed under the genus Nautilus. Towards the end of the 18th century and into the 19th century generic authors emerged and mushroomed throughout Europe; names that remain with us are Walker, Boys, Jacob, Soldani, Fitchel, d'Orbigny and of course Williamson. Although the Foraminifera have been known to microscopists for many centuries very few people actually seem to collect them. In the study of geology and within the petroleum industry in particular, fossil deposits have become familiar markers of time periods and allied climate in the formation of earth's crust. Living creatures are to be found in marine conditions from the ooze of the deepest ocean to the seaweed's of the littoral zone. They can also exist in hyposaline estuarine situations. There is even one non marine environment where they can be encountered in brackish pools of the eastern shore of the Neusiedlersee which divides Austria from Hungary. Some claim that this is a residue from the Miocene period sea which existed here 10 million years before the present time.
THE GREENHOUSE EFFECT.
If the "greenhouse effect" does become more than a theory, then it would be important to record the content of the seas around us before the sea conditions begin to change. Although the Mediterranean Sea and the North Sea share several species, each has a very distinctive "assemblage" of types. It is perhaps noteworthy that the shared species tend to be much larger in form in the Med.
Foraminifera and the shelly remains of other calcareous marine creatures would be an ideal component of the School Curriculum: The empty "shells" have considerable aesthetic appeal. They can be very numerous, and the material from shore gatherings does not require to be killed or fixed, nor would their collection affect the environment in any significant manner. Investigation would be quite suitable for low magnification, low cost microscopes. There is much scope for exercises in discrimination during identification as there is considerable variation in shape, size, colour and frequency and numbers of the various species.
THE DEPOSITION ZONES OF EMPTY TESTS.
The assemblages of species of Foraminifera vary according to the temperature, and the salinity of the sea water. Deposition in our seas is an ongoing process. Dredging can hardly be considered by the amateur. These simple yet beautiful microscopic shells can be found in the tide mark in various situations around our coasts. Bays that are larger than half a mile across are potential hunting grounds, but in tidal Northern Europe, the zone of deposition is restricted to a limited area. In round terms it can be found near the headland from which the tidal flow comes. So along the south coast of England the place to look is at the most westerly end of the bay: Weymouth, Tor Bay and Swanage are good ones to visit. Along our East coast the flow is mostly from the North and the Northern end of the bay is the one to search: Scarborough and the Wash are good sites. It was in all probability the sands of Scarborough that inspired Williamson to produce such learned work on the subject culminating in his Ray Society manual. Black coal and brown lignite have similar physical characteristics to forams and generally form an identifiable black and white banding in the tide mark with the forams. Where prevailing winds are continuous on the Atlantic seaboard, Foram Dunes can be created. The most famous of these is at Dogs Bay W.Ireland and there are others on the W. coast of Scotland like Calgary Bay, Mull. and near the north west tip of Scotland. In Bracklesham Bay and one or two other areas fossil forams from Eocene beds may be found mixed with the recent ones. In the Netherlands there can also be some confusion. In tidal lagoons like at Het Zwin, (NL) and broad estuaries like the WesterSchelde, fossil forams may be found alongside recent ones as much of the Zeeland (NL.) landscape consists of covered or exposed tertiary beds.
To the lee of sheltered headlands, growths of the Japanese Seaweed Sargassum muticum are often wreathed in colonies of the betnthic species Elphidium crispum. With a good X15 hand lens the minute shells, covered in protoplasmic threads can be found seeking the protection of nodal swellings on fronds of seaweed near the surface. Elphidium enjoys an association with various commensal algae which make the living tests appear to be green in colour, whereas dead tests are generally bleached white by the weather. Although a virtual pure culture can be obtained from the seaweeds, the tests will require thorough cleaning with hydrogen peroxide for several days.
From the shoreline this is best achieved with a small flat childrenís spade. Only the superficial material is scraped up.
DECANTING TESTS FROM AN AGITATED SUSPENSION.
THE EARLAND METHOD.
Sorting the Foram tests from the sand can be like finding a needle in a haystack but the little shells are slightly lighter than the sand . When the sample is shaken up vigorously in a bottle of water in a bright light, one can see that after one second most of the brownish sand will have settled. At that point the suspension of white tests is poured off swiftly into a 50 micron filter. One can at least concentrate the sample of Forams and wash it free from salt under the tap. When the container is almost empty for no obvious reason large numbers of tests become buoyant. It is from this observation that the "Fluid rocking" idea originated
When dried out and placed in a dish, Horizontal shaking will cause the shells to work their way to the surface where they can be picked out. The careful use of sieves can help in the sorting out of types. Sieves from 50 microns to 700 microns in steps of 50 microns are a useful range to have for this work. In the past, heavy but fairly inert chemicals like carbon tetrachloride (CTC) have been used to float off the tests but these volatile substances can affect the earthís environment and are no longer generally available.
This method copies the natural deposition of tests on the strand line. If the sample of damp sand and forams is poured into a photographic developing dish and only partly covered with shallow water and gently but slowly rocked from end to end, numbers of tests will float and can be decanted into a 50 micron sieve. This rather curious floatation seems to happen because water is strongly cohesive so when the shells are elevated above the level of the fluid, water is drawn from them and replaced by air. As the rocking is reversed they are able to float off and are buoyant for long enough, to be decanted. The only requirement is to regularly replace the water and to ensure that during the rocking process the shells emerge from the water. In nature this is exactly how the strand line of forams advances up the beach with the tide. The return of each wave draws water from the tests leaving many filled with air but the next wave floats them off and deposits them further up the beach. Material from the Mediterranean and our Atlantic coasts is very responsive to this treatment but of course fossil material filled with heavier particles of pyrite or silica will not rise on the water.
When the sample is pure enough some of the tests may not have been well weathered and these may benefit by immersion in fresh Hydrogen peroxide for several days to blanch them. This will remove some of the algal stains and unwanted organic material.
Smaller "shells" less than 200 microns may be strewn in water and when dry, mounted in Canada Balsam or a similar mountant. Its always a good idea to smear the slide first with a trace of gum tragacanth paste in order to prevent the "shells" moving after mounting. Bubbles emerge after the application of Canada Balsam for about five days and can spoil the mount. It is best not to use any heat for a week or until bubbling has finished. The larger faction will probably have to be dry mounted. A fine 0000 art brush is a good tool for manual selection. Here again Gum Tragacanth is a suitable adhesive because it tends to leave no unsightly smear. At first, a simple 1 mm deep cell with a black background is very suitable but when one becomes familiar with species then some form of numbered grid is a good idea
For those that have a serious interest in photography a coloured background might be a useful development. Sky blue or red both give excellent contrast for pure white forams and blanched marine debris. 19 mm coverslips can be painted with Humbrol, dried and then stuck to a 3x1 inch slide on a drop of the same paint. When dried, a ring may be applied and a dry mount completed in the usual manner. More recently, background has become an important factor in digital photography in which there may be automatic exposure on the overall field of view. In these circumstances white tests on a jet black background may become overexposed if there is no manual override.
This is a traditional water based adhesive for dry mounting. The gum can be made into a loose paste and applied to the cell surface in advance of the work. The key to its use is to dilute it as thinly as possible so that there is little or no trace on the slide surface when dry. A test application is essential. NBS now produce a commercial dry mount adhesive which works very well.
THE PRODUCTION OF NUMBERED GRIDS.
Many years ago I chanced upon a laid slide of Foraminifera by Mr. Firth of Belfast. I carefully dissected the masterpiece and probed under the paper covered edges. It was a numbered grid of 32 squares mounted with forams together with a hand written listing of the organisms and their land of origin. The grid consisted of white lines on a black background. The shells were in superb condition but one of two were discoloured. This led me to suspect that this chemical deterioration might be due to the decay of photographic chemicals. I suspected that the grid was a product of photographic reduction from a much larger artwork. I tried to create a grid from black scraper-board and white lay-on lettering, but the results were not very impressive. After a variety of approaches I eventually realised that the computer might be of assistance.
COMPUTER DESIGN OF THE ARTWORK.
The squares can be produced in a variety of ways. Little squares can be copied and compounded using the "Paint" software or the grid of "Micrographx" may be used with the snap-to-grid feature, to build up the network of lines. This software can be purchased with Avery labels at W.H.Smiths for under £10,
Incidentally it is also useful for labels and calling cards of course and layouts for exhibition. The general idea is to produce black lines and letters on a white background as a bitmap image. The grid can be numbered as required. It's a good idea to surround the thing with a neat circle. Next the whole image must be captured and a mirror image can be created by flipping in the horizontal plane. This is then printed from the computer. The finished work should be not larger than four inches in diameter.
PHOTOGRAPHIC COPYING OF THE IMAGE.
A text copying machine can be used, or better still the image can be laid onto the base-board of an old enlarger, but one in which the lamp, lens and film support is replaced by an old pentaprism 35mm camera, (Zenith or Pentax) at about 50 inches high. With a little luck the camera will fit into the old lamp bracket. The function of the enlarger apparatus is thus reversed and it becomes a reducer. In the darkroom the photographic paper is cut up into 35mm strips and negative stage, makes for a much clearer print. The artwork can be illuminated by two 40 watt bulbs on either side at an inclination of 45 degrees. Manual sharp focusing can then take place using the viewfinder of the camera with the f number set low at f2. An exposure is then made from 10 to 25 seconds with the f number at 16 or higher. A high f number and tiny aperture is essential for clarity. The paper is developed in a darkroom using paper developer and paper fixative in jam jars under a red light, to be followed by washing. Test strips are a useful preliminary operation.
FIXING THE RING.
The thickness of 19 mm diameter aluminum ring chosen depends upon the subject material. 1.5 mm thickness is ideal for the rather large Mediterranean species but 0.75 mm is probably better for run of the mill North Atlantic. After drying the photographic paper, a 19 mm aluminum circular ring, is stuck on the emulsion side by laying it on centrally, after treatment with 3M spray or contact adhesive. Paper around the ring is then cut away, and the artwork is then stuck to a black ringed 3x1 inch slide also after spraying with the 3M adhesive. The printed emulsion surface is water absorbent and ideal for gum tragacanth which leaves less of a smear than most adhesives. To secure and reinforce the contact adhesive itís a good plan to ring the assembly with a liberal layer of gold size.
LAYING THE TESTS.
The gum tragacanth is best mixed fresh because degenerated material merely adds to the mucilage and adds nothing to adhesion. It is perhaps useful to note that many of the Norman cells that I investigated that were lined with black paper, had already been smeared with gum which was still tacky when moistened many decades later. (See Homepage at http://www.darnton.freeserve.co.uk.) There are various options in gumming: When mounting small numbers, a minute blob can precede each laying or a much diluted gum can be applied to the whole of the grid area. This is a matter for ones own preference. A thinned 0000 brush is a useful tool for the transfer of tests.
When large numbers of forams are to be laid, then the use of store slides is a useful intermediate stage. NBS sell some green or black plastic slides with deep cavities which can be fitted with a protective cover-slide which come from Australia. The tests can be gathered in drops of distilled water in the labelled cells which can be later dried out ready for the ultimate selection. When the laying and drying is quite complete, the coverslip can be stuck on a nearly dry layer of goldsize and then a day later ringing over the junction of glass and aluminum can take place. Since these deep type slides can only be used with low power magnification there is little point in using very thin cover-slips and size 3 is quite suitable.
The older mounters invariably and wisely used a glossy black shellac that at the same time covered any irregularities in their work. Shellac besides being an excellent protective waterproof ring, is soluble in alcohol, a solvent that will evaporate quickly. It will not re-dissolve the more common mountants which are normally xylene or toluene based. It will also resist the effects of immersion oil. It is possible to produce the ringing cement from shellac flake and isopropyl alcohol. The consistency of the fluid is the great problem. If the liquid is too dilute in the alcohol then it will run, obscuring both the slide and the coverslip, if it is too saturated in shellac then it will become lumpy and uneven in application. Preparation of this material is a 14 day business at the very least. A stock jar of flake shellac is half filled with isopropyl alcohol and left at room temperature for about a week. The liquid is poured off, filtered, labelled, stored and tested. If it is still rather fluid then leave the lid off the jar until the correct consistency is reached by testing on a blank slide. After frequent use it does become lumpy and uneven from evaporation and a few drops of alcohol will be required from time to time. Remember that the brush should be stored in a small bottle of alcohol through a tiny hole in the lid. The stem of the brush may supported by a cork to prevent the bristles from flattening on the bottom.
Shellac is normally golden in colour and I have spent many months trying to find a blacking agent. The most suitable product has been black technical ink sold for stiletto pens. It is miscible in alcohol and does not interact with xylene or toluene based mountants providing that they are dry. NBS in the UK do produce and sell a shellac ringing material but it has a slightly purple hue. They also produce a wonderful golden shellac called Bioseal No. 2 which is an alcohol based shellac. This is what I use nowadays, but I blacken it with the technical black ink by Faber Castell. Only a few drops are required and then one must leave the lid off until it passes the consistency test on a blank slide.
The brush (No.1) should be dipped in the alcohol storage bottle and then in the stock solution of black shellac. It's better to apply the ring with a generous covering in one session so that any bits may fall to the bottom never to be seen again. When several applications are applied over a few days the uneven features tend to be amplified rather than be obscured. Black ringing for those who may find it dull, may be ornamented at a later stage with a thin ring of white zinc paint when dry, or coloured model paint coded for subject may be used i.e. blue for marine, green for freshwater etc. Shellac is very useful in the process of conservation but one must beware of using it on alcohol based mountants of course. The uncovered alcohol saturated mixture is inflammable and although the very small amounts represent only a small hazard, the jar must be stored in a ventilated protected area. There are details and variations but that is the general idea.
Summary of Requirements:Old 35 mm camera like Zenith
Old B+W enlarger
Paper developer and fixer
Jam jars for fluids
Dark days of winterBlack and white photographic paper. The paper should be first examined under the microscope for texture. Matt is the best material, but straight gloss is better than the modern papers that have all manner of reflective bits in the surface under the microscope these can be very distracting.
Although a grid may be drawn with traditional drawing instruments under a hand lens, photographic reduction offers a greater degree of neatness. Computer assisted design is now quite simple using the software "Micrographyx" to create numbered grids within a four inch circle. The negative phase of reduction can be avoided if the image is reversed by flipping in the horizontal plane before photography. After attaching an aluminum ring the completed grid can be stuck onto a prepared 3x1 inch slide and the tests can be laid within the squares using diluted gum tragacanth. After drying the cover-slip can be applied, sealed and a black shellac ring applied. Labelling must not be neglected.
Mounted Foraminifera from home or distant oceans were a familiar attraction of the Victorian microscope cabinet. World travel is now open to a much larger portion of the community, therefore there is no reason why an interest in these fascinating creatures should not be rejuvenated. Our own European seaside will provide a very good introduction to the subject.
RECENT LITERATURE ON THE FORAMINIFERA.
AN ATLAS OF RECENT FORAMINIFERA by J.W.Murray.
1971 ISBN 0 435 62430 X Heinemann Press with 96 SEM plates.This work contains the main comprehensive listing with illustrations of those recent species common to the British Isles. Not all the rarer types that come in onto our west coasts on the Atlantic drift are included. Estimated second-hand cost £15-£35.
THE CHALLENGER FORAMINIFERA by R.W.Jones
1994 ISBN 19 854096 5 Oxford University Scientific Press. This is a beautiful reprint of two of the Challenger volumes. It contains the Original coloured illustrations with a thoroughly updated listing of species and their locations.
In addition there is a resume of the voyage of the Challenger and a version of the Brady Biography. Recently in print new at £180.
FORAMINIFERA by J.A.Cushman.
1980 fifth printing ISBN 674 30802 8 Harvard University Press. This is a standard text for global fossil and recent Foraminifera. The illustrations are white on a black background and superbly done. There are normally two volumes but sometimes they are bound together. The text must be regarded as not altogether up to date, but perhaps updated versions now exist. Cushman published several general and specific works on the subject during his lifetime. Estimated second-hand cost £8-£20
SYSTEMATIC INDEX OF RECENT AND PLEISTOCENE PLANKTON FORAMINIFERA byT. Saito et al.
ISBN 0 86008 280 6 University of Tokyo Press 1981. This is a splendid book with excellent SEM plates but is confined to Plankton species as per title. Estimated second-hand cost £10-£15.
FORAMINIFERA by J.R. Haynes.
This extensive text book contains 15 actual plates and over 100 text figures. Many of these contain fossil and sub-fossil listings with diagrams and illustrations, but the publication falls short of being a Foram atlas as such. There have been reprints and a not very recent value was about £64 new.
FORAMINIFEREN FOSSIL EN RECENT by Dr. E. Th.N. Spiker.
Wetenschappelijk mededelingen Nr. 99 KNNV November 1973.
With 281 Monochrome Figs.
The very useful plates are contained in a detached working folder that is separate from the main Dutch text. This was a very inexpensive production but would only be obtainable in the Netherlands second-hand.
As well as ordinary book shops there are on line technical book shops. If they have a search engine attached, a good one would be expected to bring up around 40 references using the keyword "FORAMINIFERA". In this subject, the work of Cushman seems to be the most commonly available. His FORAMINIFERA is valued from US$20 to US$30 from the United States but expect postal charges (Shipping) of up to $35.
In the United Kingdom, Savona Books at 400 Seawall Lane, Haven Sands North Cotes, North-East Lincolnshire DN36 5XE will always oblige with a priced catalogue which often has books in this field.
Ref. 1. Aldrovandi U. MUSEUM METALLICUM 1648 page 711 Cap. 157. A good copy exists in the Natural History Museum, South Kensington, London.
Ref. 2. R Hooke MICROGRAPHIA 1665 pub. J. Martyn and J. Allestry reprinted under Dover Books in 1961. Estimated second-hand of the Dover version costs £10-£25.
Ref. 3. C.Dobell ANTONY VAN LEEUWENHOEK AND HIS LITTLE ANIMALS London 1932. New York (Dover Books) 1960. Estimated second-hand of the Dover version costs £10-£25
Ref. 4. Carl Linnaeus SYSTEMA NATURAE 10th ed. 1758-1759. This can also be found in the Zoology library of the Natural History Museum.
Ref. 5. Dr.B Bracegirdle. MICROSCOPICAL MOUNTS AND MOUNTERS 1998 ISBN 0-9614441-3-1 contains several references to Foram mounters as well as illustrations of slides. Obtainable from Savona Books qv above.
OTHER ON-LINE LINKS.
The Kane Scientific Company of 109 Hicks Lane, Great Neck, NY 11024, USA at:- http://www.kaneforam.com/index.html sell 3" models of the main 40 genera of the Foraminifera. Four pages of photographs of these 40 models can be downloaded from the site. These in themselves are very useful educational aids for those who would like to become familiar with the external morphological characteristics of the main genera.
Comments to the author, Comments to the author sent via our contacts page quoting page url plus : ('bdarnton','')">Brian Darnton, are welcomed.
The author's home page which has further resources on the forams is at http://www.darnton.freeserve.co.uk
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