[The size polymorphism of the cercariae of a Venezuelan strain of Schistosoma mansoni].

By mean of the silver impregnation of a lot of 47 cercariae belonging to C5 venezuelan Schistosoma mansoni strain, a polymorphism of size was evidenced. The morph was conformed by the greatest cercariae (between 152.9 microns to 218.4 microns). This group was ever present in the population of cercariae in less percentage (29.8%). The length of the normal cercariae was comprised between 119 microns to 152 microns. This group was the dominant in the population: 70.2%. The comparison between the length of both lots of cercariae resulted with significative statistical differences (t = 5.5; P < 0.001). For the total studied cercariae the average of the length was X = 143.9 microns and for the wide X = 68.6 microns. It was found a positive significative correlation between the wide and the length of the cercariae r = 0.83 (P < 0.001).