A Comparison of Preparation Techniques in Taxonomic Studies of Longidorus africanus Merny.

A comparison was made of ten different techniques for killing, fixing, and mounting Longidorus africanus Merny for microscopic study. The most satisfactory specimens were those killed by Seinhorst's method, fixed in FAA and mounted in glycerin by the slow method. Specimens killed by "gentle heat," fixed in FAA and mounted in glycerin were also acceptable as were those killed by hot formalin and mounted in glycerin or processed by Baker's method. Less satisfactory were: nematodes killed by "gentle heat," fixed in formalin and mounted in glycerin and specimens killed by vapor phase perfusion or by Hopper's lethal stain, both latter groups were mounted in glycerin after fixation in formalin. Killing with cold formalin, gradual heat (60 C for 15 min), or by storage in distilled water produced poorly defined specimens. Nematodes killed by hot formalin, and processed to glycerin by the slow method, maintained their live dimensions. Reduction in length occurred in specimens killed by cold formalin, by storage, or treated with solutions containing acetic or propionic acids. Nematodes processed by Baker's method increased in size. Other minor modifications occurred in specimens processed by the different methods. Esophageal definition was best in nematodes killed with formalin, hot or cold. There is no correlation between position of the posterior part of the esophagus and position of the onchiostyle.