Kicro:l 



SPECIALIZED MICROSCOPY FOR THE STUDY OF NEMATODES 

 Eldon J. Cairns 



It is not very long before the critical worker in phytonematology comes 

 to realize that the standard research microscope and the binocular 

 dissecting microscope sometimes leave much to be desired when it comes 

 to close study and observations of nematodes. Have not all of us vjlshed 

 for some new and presumably better high-powered microscope in order to 

 make certain routine but decisive determinations concerning structures 

 of nematodes which are near the 0.2 ji resolving limits of our instmments^ 



Have you ever thought of how very little we know of the actions of the 

 nematodes in or on their hosts or in the soil because of our inability 

 to directly observe the nematodes with sufficient magnification to see 

 what is going on? The objective lenses of our research microscopes have 

 30 limited a working distance that at the necessary high magnifications 

 they cannot be brought to focus on anything over a fraction of a milli- 

 meter distant. The stereoscopic dissecting microscopes, which are 

 aesigned for ample working distance, do not have sufficient image 

 quality at their highest magnifications, which are not high enough. 



Another of the problems we face is not necessarily one of seeing very 

 small structural sizes but is the transparent nature of the specimens 

 we want to view. New ways have been developed to meet this common 

 problem in the microscopy of biological materials. Some of you may be 

 looking for new research tools having quantitative and qualitative 

 applications in the study of the tiny nematodes and of their hosts ' 

 cells and tissues. 



Without going into extensive details in any parts of this discussion, 

 we shall consider a few of the specialized instnmients and methods of 

 microscopy indicating how they operate, their advantages and disadvan- 

 tages. Perhaps, you may find from this discussion solutions to particu- 

 lar problems, or you may get an idea for new and rewarding lines of 

 research in phytonematology. 



Electron Microscopy 



If the problem at hand is one requiring the greatest magnification and 

 resolution, then it is natural to think of utilizing the electron micro- 

 scope. Unfortunately for us, the scarcity of such instruments is not 

 the only deterent for their application to nematology, as I shall explain 

 later. The electron microscope is without equal for its resolving power 

 and useful magnification. Current models can resolve to 20 Angstrom 

 Units (.002 }i). Direct magnifications range from about 100 diameters up 

 to 50,000 diameters. Fine grain panchromatic photographic fiLns or 

 plates exposed at such magnifications can be further enlarged optically 

 with increased benefit yielding final specimen magnifications up to 



