VARIATION WITHIN THE INTERNAL TRANSCRIBED SPACER (ITS) OF RIBOSOMAL DNA GENES OF INTERMEDIATE SNAIL HOSTS WITHIN THE GENUS BULINUS (GASTROPODA, PLANORBIDAE)

Species within the genus Bulinus are responsible for transmission of s chistosomes within the Schistosoma haematobium group. In order to prov ide a molecular insight into the species relationships within the genu s, genetic variation between species representing the four species gro ups was assayed by Polymerase Chain Reaction (PCR) amplification of th e ribosomal Internal Transcribed Spacer (ITS) region followed by Restr iction Fragment Length Polymorphism (RFLP) analysis of this product wi th six restriction enzymes. This PCR-RFLP methodology detected conside rable variation within the ITS region indicating that restriction prof iles will be useful as genetic markers for identification purposes. Th e complete ITS1 spacer was sequenced for B. globosus, B. cernicus and B. truncatus. There were numerous nucleotide differences between taxa mainly insertions and deletions. Nucleotide divergence was calculated between species from the restriction profiles: the B. truncatus/tropic us complex and B. reticulatus group were most similar which were in tu rn more closely related to the B. africanus group than to the B. forsk alii group. The nucleotide divergence between the species groups is su bstantial and questions the placement of these groups within the same genus.