The Technique of Mounting Foraminifera
The foraminifera are amoeboid protists. They are the most
common marine planktonic and benthic species. The majority of the shells of
foraminifera (from Latin foramen, an aperture) have a number of tiny openings
throughout their entire surface, so that finely extended feelers or pseudopodia
(from Greek pseudo, false, and podia, foot) may protrude in all directions. These
marine rhizopods constitute the most important order of this class of life. They
have existed from very early geologic time, and their remains have contributed
to the formation of present-day rocks.
Most of them live on the bottom of the ocean and seas, and
are food for sponges and other creatures. Large numbers, however, live on the
surface of the ocean and seas, and their dead shells continually descend to the
depths where they form ocean mud, as in the case of “Atlantic ooze.” The
globigerina are one of the many classes of marine rhizopods, and are, in
reality, a group of foraminifera.
Most of the foraminifera shells are made up of calcareous or
chalky matter that the organisms secrete from elements present in the
surrounding sea water. Some, however, have shells that are in part calcareous
and in part tiny particles of sand. There are also those whose shells are
entirely made of sand grains cemented together. The shells are partitioned into
many chambers, and many of the shells are in the form of a spiral, like those
of the nautilus and ammonite. Generally very difficult to distinguish with the naked
eye, they are readily detected with a good pocket lens.
WHERE TO FIND FORAMINIFERA
There is no great difficulty in finding samples of these
beautiful shells for examination with the microscope. In the sea, you can
collect them, and then observe living foraminifera. On the mainland, you can
find soils rich with fossil foraminifera on all continents. Look for them on
land that in ancient times had been submerged by the sea. Even the sand of the
beach may be interesting to observe. In the midst of the grains of sand, you
can find tiny shells, snails, and tiny fragments of marine organisms.
It is a wonderful thing to look with the stereoscopic
microscope at sand from the Pacific Islands or other exotic localities, and
find that it consists almost entirely of small shells of marine animals.
For collecting foraminifera, you can go to the waterline and
pick up calcareous material from the surface with a spoon or plastic card and
insert it in plastic bags or vials. On a beach, take several samples from
different places in order to increase the probability of finding foraminifera.
A little 10X lens also helps. Then label the date and localities where you have
collected samples. When you arrive home, wash the sand samples to eliminate
salt, and then dry them; insert into little vials for storage.
For mounting foraminifera there are some minimum materials
- A stereomicroscope (10X to 40X)
- Glue for fixing the foraminifera to the slides (Tragacanth
- A little brush 000, or a fine self-built needle
- Microfossil slides of two types
- Rigid white paper
For gluing microfossils to slides, use a commercial glue made for mounting microfossils (Figure 1), or prepare glue yourself using Tragacanth gum (Figure 2). Gum Tragacanth is a suitable adhesive because it tends to leave no unsightly smear, and it is easy to prepare by mixing powdered Tragacanth with water; it also has the advantage of being removable.
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Figure 1. Commercial microfossil glue.
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Figure 2. Tragacanth gum.