|Wergin, William - COLLABORATOR, USDA, ARS|
|Moser, William - SMITHSONIAN INSTITUTION|
Submitted to: Microscopy and Microanalysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 9, 2001
Publication Date: N/A
Interpretive Summary: Thousands of species of nematodes, mites, insects and leeches 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 these organisms and to distinguish those that are harmful from those that are not. The current study, describes a procedure that freezes examples of these soft bodied organisms 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 organisms at magnifications of more than 20,000 times. This enables them to describe their detailed structure and to relate them to other forms that are known to be harmless. Comparing organisms in this way provides scientists with information that can be used to identify potentially harmful organisms 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 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 soft-bodied species of organisms such as mites, insects and leeches 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 several widely diverse soft-bodied microorganisms. Results indicate that cryofixation, which is associated with this technique, maintains the organisms at their living/feeding sites. Furthermore, the turgor of the specimens is also maintained. The structure of delicate features, such as setae, which are subject to mechanical damage 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 not previously observed. These advantages indicate that LTFESEM is an important technique that can provide complementary data for taxonomic descriptions of widely diverse soft bodied organisms.