Wednesday 13 May 2020
Friday 3 April 2020
Wednesday 24 December 2014
After making slides of canada balsam in which the tests are protected by supporting the cover slips by small tabs of various diameters and thicknesses, other problems emerged; When near transparency finally emerges, it becomes evident that the tests need to be far cleaner than for dry mounting, so an extra cleaning stage needs to be introduced. The first effort with hydrogen peroxide might be helping but long term immersion will be needed at the very least.I hope more lucid images will emerge. Please remember to click on the image to make it larger.
Sunday 6 July 2014
Budding or not?
This is an image of probably Haynesina germanica . Is was an empty test found in a deposition zone in Poole Harbour. Each Summer these tests and those of some others like Elphidium Williamsoni are found on the shores of the Harbour.
I have always assumed that the capsules were the primary chambers of a budding adult but I cant find very good images around the net to confirm this can anyone help . Brian Darnton.
The foram is ot cleaned but mounted in Canada Balsam without pressure .
Wednesday 4 June 2014
The Foraminifera of the Swanage Shores.
These beautiful
shell like creatures can only be seen with a good hand lens or better still a
simple microscope. Our local species are only a fraction of a millimetre in
diameter.
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What is rarely
appreciated is that they also flourish today as living creatures in the open
sea as part of the plankton and the estuarine areas of river as at Poole. Foraminifera are actually closely related to
the Amoeba of our school text books but they grow a shell like structure called
a test to protect themselves from the many hungry creatures of the seas. There
are no organs and these animals belong to the Protista: the simplest and
earliest of creatures to appear on Earth. The tests are made of various types
of chalk (calcite). Some species seem to be almost transparent, being
constructed of crystalline calcite, but others seem to be paved with porcelain
like chalk but in the river mouths where there is less chalk dissolved in the
water, they are protected by particles of sand or debris bonded onto a covering
of a chitin-like material. These are called arenaceous species. The
Foraminifera are clearly masters of adaptation as well as being climate
indicators. Generally the white tests are noteasy to find because they are very
small but in deposition areas they can be found en masse, usually mixed with
black sea coal from industrial spillage and ship wrecks. This gives these sites
a black and white banding which is easy to spot
(See above Right). In Swanage Bay an
area can be discovered between the Mowlem building and the Public Hard at low
tide. Washing, sieving, drying and floatation in clean, fresh water all help
to improve the sample.
As well as Swanage, Weymouth and
Fleet, there are local deposits within Poole Harbour near the Salt
marshes at Arne and Redhorn Quay where they lie almost unseen, amongst the
small washed up shells. The ornamental tests of these invertebrates are
objects of considerable aesthetic appeal and beauty as well as having a
significant scientific interest. The two illustrations above, clearly show
the difference between the Open Sea British Channel fauna of Swanage Bay and
the estuarine fauna of Poole Harbour below with a proportion of gritty arenaceous
types, which are very ornamental in polarised light.
Tuesday 2 July 2013
TEST OF FRESH WATER DIFFLUGIA SPECIES
TEST OF FRESH WATER DIFFLUGIA SPECIES FROM SWANAGE BAY
Test in Simple reflected light
Test in crossed Polars with Victorian selenite plate
(N.B.Another test)Polar with cossed polars no plate
Quite often one change leads to a complete change of direction. I have been aware of the deposition of Fresh Water tests of testate amoeba in Swanage bay for several years but have rather overlooked them as an object of interest.
After several years of Dry mounting I have moved over to aspects of Mounting in Canada Balsam. and this has enabled photography using traditional methods such as Bright field, Dark field, and photography of arenaceous tests of foraminifera in polarised light.
More recently I have tried polarised light not only at full extinction of direct light but also when using various Victorian selenite plates. These effects are rather unnatural looking and much less sharp but never the less they are quite compelling. I include my first effort as the coloured image above. The less colourful one below is a test from several years ago shown for comparison.
The diversity comes from the external protective layer of particles bonded onto the internal bag of equally protective chitinous material.They are of various thickness each distinguished with its own colour dependant upon its structure and thickness.
Thursday 13 December 2012
This Post has been added to explain the idea of moving over to the mounting of Forams in Canada Balsam
The mounting of Foraminifera in Canada Balsam without
Pressure.
Foraminifera tests are more usually mounted
dry to enable more natural views of these small shell like creatures to be
observed.
Although More frequently Mounted dry, the mounting
in Canada Balsam has surprising results. At the Turn of the centuary in 1900
Joseph Wright the clear leader of the Belfast “School” of Forams, discovered
that Canada Balsam mounting improved the clarity of vision and was particulary
lucid for arenaceous tests. He makes a clear statement in his account of the
Foraminifera of Rathlin Island.
QUOTE from THE IRISH NATUALIST VOL 11 in
1902 page211 from old copy
I
have since examined with transmitted light specimens mounted in
Canada balsam, and by this means. I have been enabled to see
most distinctly the arrangement of the chambers throughout the entire test. I
have examined In this way about 150 from dredgings taken off the Irish coast,
including These Rathlin specimens, with a large number of fossil specimens from
the Chalk of Co, Antrim; also the only perfect specimen, which I had of the variety
fistulosa, Brady, from Raine Island Torres Straits 166 fathoms. In all Cases
both the recent and fossil specimens when perfect had the early chambers
arranged in a spiral manner. Further
research since 1888 hasTherefore confirmed me in my belief that this
species is truly a Spiroplectaand not a
Textularia.
End of Quote
However those species
constructed of crystalline calcite do become quite transparent when mounted in
Canada balsam. The full beauty of the three dimensional spiral then becomes
both evident and optically enhanced. The tests must be much cleaner than
normally used for dry mounting and up to three days immersion in an open vessel
of hydrogen peroxide may be required followed by washing in a fine sieve of pure
water. The initial problem however, is ridding the mount of air bubbles before
mounting commences. The tests may be laid as a small central strew or equally
well they may be laid in a geometric or taxonomic array, depending upon the
quality of material available. The tests can be secured to the glass with the
Gum tragacanth more traditionally used for dry mounting and when dry, the
slides can be immersed in toluene overnight in a Coplin Jar half filled with
the solvent. Quite often vacuoles of air are trapped and unable to escape from
the natural apertures within the test, so before mounting, the need to be examined under the microscope.
Species of the Lagena genus only have one small aperture so the slide may need
to be inverted several times over two to three days. When the expulsion of air
is complete, the slide can be laid on a hot plate and two drops of Canada
balsam applied with a pipette and a coverslip laid. Since the tests are quite
thick and brittle compared to other micro-organisms the slip must be applied
without pressure and the simplest and best support is the use of three
peripheral disks of around 0.5mm thickness 1.5mm diameter. The disks should be
bonded to the coverslip before mounting using glass bond in sunlight followed
by washing in toluene and drying with paper tissue before use. The cutting tool
for these is flat nosed pliers drilled out for a piston on one side and a complimentary
hole on the other These tools are actually available for the amateur Jewellery
trade. Any burrs may be rubbed down on fine emery paper. Suitable brass or
aluminium sheet from model shops can be purchased in various thicknesses but
having been produced in the USA the measurements then tend to be imperial
rather than metric. A vernier gauge is also a useful tool for this work of
course. The space afforded by the three small discs also enables spontaneous bubbles
to escape quite freely during the drying process. After several days of
hardening the surplus balsam can be scraped away with a scalpel and the work
can be ringed and protected with black shellac in alcohol and dried. Suitable
labelling may then be applied. BD DEC 2012
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