|Craemer, Charnie - AG RES COUNCIL S AFRICA|
Submitted to: Scanning
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2000
Publication Date: N/A
Interpretive Summary: More than 10,000 species of mites infect nearly every agronomic and horticultural plant important to agriculture. In the United States, these pests cause annual economic losses from decreased food, fiber, and ornamental production estimated to be in the billions of dollars. One problem facing scientists is their inability to observe the detailed structure of mites and to distinguish those that are harmful from those that are not. The current study decribes a procedure that freezes mites so that they can be observed in a very powerful microscope known as a field emission scanning electron microscope. With this instrument, scientists can observe the mites at magnifications of more than 20,000 times. This enables them to describe the detailed structure of new mites and to relate them to other forms that are known to be harmless. Comparing mites in this way provides scientists with information that can be used to identify potentially harmful mites and to suggest procedures that will help reduce the damage that they cause. In addition, this information will benefit the public by identifying new and potentially harmful species of mites before they are introduced into this country.
Technical Abstract: Because of their microscopic size and fragile nature, it has been estimated that less than ten percent of the mite species are taxonomically described. Recently, data from scanning electron microscopy (SEM) has been used to facilitate and complement the information that is obtained with a light microscope. However, the preparation techniques associated with SEM frequently prevent or compromise the results. This study evaluates the use of low temperature field emission (LTFE) SEM to image mites. Results indicate that cryofixation, which is associated with this technique, maintains the mites at their living/feeding sites. Furthermore, the turgor of the specimens, including eggs and soft bodied species, is also maintained. The structure of delicate features, such as setae, which are subject to mechanical damaged during chemical fixation, dehydration and drying, are well preserved. Field emission SEM, which provides useful magnification beyond that attainable with a conventional SEM, also enables resolution of ultrastructural features, such as pores on the surface of the solenidia. These advantages indicate that LTFESEM is an important technique that can provide complementary data for taxonomic descriptions of mites.