The use of aceto-orcein-stained squash preparations for enumeration of nuclei in microfilariae of various filarial parasites.

The nuclear numbers of situated between the cephalic space and the nerve ring (CS-NR) in the microfilariae of six filarial species were examined. For the counting of nuclei, aceto-orcein squashing preparations were used. This procedure revealed nuclei clearly visible under the phase-contrast microscope. The mean number of nuclei in the CS-NR region was very similar between Brugia pahangi and B. malayi, but was statistically different between Onchocerca volvulus and O. gutturosa. In the microfilariae of O. volvulus, two types of nuclei were clearly shown in this region. The procedure described is useful in the anatomical study of microfilariae.