[Cercaria chaetotaxy of 2 Venezuelan strains of Schistosoma mansoni].

By means of the silver impregnation of two lots of Schistosoma mansoni cercariae belonging to the strains: JR (32 cercariae) and C5 (45 cercariae), the number and pattern of disposition of the argentophillic papillae were determined with the following results: Average number of total dorsal papillae: 12.1 (JR strain) and 12.0 (C5 strain); the variation coefficients in this surface were less than 4% (JR strain) and bigger in JR than C5 strain. Average number of total ventral papillae: 12.15 (JR), 11.97 (C5); maximum value of the variation coefficient: 6.4% (JR), higher in JR than C5 strain. When the ventral surface was classified in four quadrants, the average number of papillae by quadrant was: quadrant A: 1.15 (JR) and 1.06 (C5): B: 1.06 (JR) and 1 (C5); C: 4.97 (JR) and 4.96 (C5); D: 5.03 (JR) and 4.98 (C5). The variation coefficients were higher in the A and B ventral quadrants, reaching maximum values of 31.9%, and 61.0% for the posterior quadrants C and D. When the ventral surface was divided in three equal parts for determining the position of the most variable papillae of this area, the greatest value of the variation coefficients obtained were for the 2nd thirds of the cercariae: 89.8% and 76.8% for C5 strain and 43.5% and 56.8% for JR strain. In relation to the total lateral papillae, the average numbers were: 17.0 (JR) and 16.6 (C5), with a maximum value of variation coefficient of (8.1% (C5). The average total number of papillae of the tail were: 25.6 (JR) and 26.1 (C5) for the ventral surface and 20.72 (JR) and 21.33 (C5) for the dorsal papillae. The comparison between the percents of the cercariae of two S. mansoni strains with more than 1 papillae on the anterior ventral quadrants A or B (94% JR and 34% C5), resulted with significant differences (P < 0.05).