Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 27. (Budapest, 1994)

Device and technique for preparing and mounting sections of helminths for morphological studies Vulko Y. BlSERKOV and Nesho CHIPEV Institute of Parasitology, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Block 25, Sofia 1113, Bulgaria Recent morphological studies for helminth identification and taxonomy often require precise sectioning of different parts of the worm body. Sectioning has been increasingly used in studies on the morphology of nematodes, cestodes (tetrabothriids) and trematodes (echinostomes). Available sectioning techniques using microtomes, although precise, are time-consuming and expensive. On the other hand, free-hand cutting with a razor blade is imprecise and requires much experience. Those methods raise serious problems when rare or type material is studied. In this paper an easy-to-make device is described and techniques for preparing high-quality sections of parasitic worms for morphological studies are suggested. Construction: The device consists of a brass stand and an arm (holder) with a fragment of a razor blade affixed on top of it. The holder is connected to the stand by a horizontal axis which allows the holder to turn around it vertically. The center of the axis is at 1.5 cm above the plane of the object. The horizontal movement of the top of the blade (up to 0.5 mm) is achieved by applying small horizontal pressure on the holder. The device is fastened to the table of a stereomicroscope with a screw in one of the available holes. The knife is made from a razor blade. Preliminary preparation and cutting: Fixed worms preserved in any fixative can be processed. Prior to cutting it is advisable to include the material in 10% glycerol or to have it dehydrated in alcohol series and placed in eugenol. This procedure allows sections to be afterwards mounted both on temporary and permanent preparations. A clean glass slide is covered with a transparent piece of polythene (of about 0.25 mm thickness) and the material to be sectioned is placed on it. Using the stereomicroscope the exact place for cutting is found and sections are made by a gentle swing of the holder. The polythene cover preserves the blade from blunting and assures a soft base for easy cutting. The sections obtained in this way have a thickness of about 30 microns. The technique above described has the following advantages: (1) simple construction of the device which is also easily attachable to a steremicroscope; (2) simple preliminary preparation of the material; (3) easy processing and high quality of the sections. Mounty sections on slides: Place a drop of glycerol in the middle of a clean glass slide. Transfer the section to the middle of the drop with fine needles (or with a pig eyelash for thinner sections) under a stereomicroscope. Slightly move the section until reaching the slide surface and place the coverslip. If the method of Maeseneer and D'Herde is used sections should be placed into a drop of dehydrated glycerol positioned within a ring of paraffin and heated to melt the paraffin. Preparations made using these methods can be studied by immersion. Mounting in glycerol jelly is also possible. Sections processed in eugenol are transferred into a drop of eugenol for immediate study or into a drop of Canada balsam for producing permanent preparations. Various sections of nematodes processed using the described device and techniques are presented in Figure 1.