Explain the Electron Microscopy In Taxonomy?

Morphological features that are easily observable with the naked eyes or with the stereomicroscopes permit quick identification and still dominate taxonomic studies. The invention of the electron microscope has made it further possible for  taxonomists to obtain useful data from the study of the ultra structure of various morphological characters. This is because electron microscope studies have revealed differences in the finer structures of the morphological characters which looked the same when studied with the naked eyes or under the light microscopes. Thus, this new method of study has led to the discovery of new and more reliable characters.

The scanning electron microscope (SEM) is now being used extensively in systematic study. It is being used very often in the study of invertebrates, particularly the arthropods. This is because there are. many fine features in insects, mites, ticks and other small arthropods which can only be observed when highly magnified by the SEM. As you are aware the SEM in comparison to the light microscope has a much greater magnification and resolution. Furthermore it gives a depth of focus which is about 300 times more than the light microscope. Thus, the SEM provides excellent, quasi three dimensional images of the body surface c e with a magnification of 50 to 10,000 x.

The scanning electron microscope has aided, for example, in the biosystematics study of tick Argas. In Argus the SEM studies have also helped in finding out new characters in addition to revealing unsuspected details of other characters which has led to the discovery of new species and also preparation of dichotomous keys.

This type of work is still being carried out in other groups of invertebrates and it is hoped that it will lead to the resolution of a number of species complex, so that classification would be simplified to a great extent.

Another type of microscope used for studying the finer details of morphological characters is the transmission electron microscope (TEM). TEM has greater magnification than the SEM and has been used to study very thin sections of the organs of the organisms, eggs and embryos of the organisms or of the whole organism itself. .It has proved extremely useful in those organisms which have very few external surface features, such as the protozoan's. For example, it has helped in the identification of two very closely related genera of protozoan-Ameoba and, The cameoba and the biosystematics of the planarians Turbellaria. However, TEM so far has been used less in comparison !o SEM in systematic studies. TEM studies have also helped 'in the identification of two economically important fruit files Dacus olae and Ceratitis  capitata (Diptera: Tephritidae) whose eggs show superficial similarity in shape and size and are separated only on the basis of character of anterior pole studied under the SEM. However, TEM studies of the eggs show additional, distinct differences in their eggs shells.