THE VARIABILITY OF THE NUMBER OF ROSTELLAR HOOKS IN TWO SPECIES OF ECHINOCOCCUS FROM NORTH AMERICA

Abstract

Examination of six populations of E. multilocularis sibiricensis and nine populations of the Canadian Echinococcus has shown that in all of them the number of rostellar hooks was extremely variable. Over 90% of scoleces of the first species had from 20 to 32 hooks, the mode being 28. Over 90% of scoleces from the second species had from 28 to 40 hooks, the mode being 32. The difference between the populations was always statistically significant, despite a considerable overlap of the summary variation curves. Of the scoleces of the Canadian E. granulosus, 98.5% lie within the limits of variation pointed out by Leuckart for the European E. granulosus, 28 to 50 hooks.