MOLECULAR CHARACTERIZATION OF MITOCHONDRIAL-DNA PROVIDES EVIDENCE FORTHE RECENT INTRODUCTION OF SCHISTOSOMA-MANSONI INTO AMERICA

Mitochondrial DNA was analyzed from 6 strains of Schistosoma mansoni w ith 12 restriction enzymes, corresponding to 40 restriction sites or a bout 1.5% of the coding region. An extensive length polymorphism among strains of S. mansoni was found, with size ranging from 16 500 bp to 24 900 bp. Five restriction sites among 40 were polymorphic; phylogene tic analysis using parsimony criteria supports the idea that American strains were introduced very recently from Africa. Two large fragments (2800 and 5400 bp), representing half of the coding region were clone d. The location of some genes was determined using heterospecific mult igenes probes and suggests that this platyhelminth genome differs from all other known mtDNA gene organization.