Schistosomes have a comparatively large genome, estimated for
Schistosoma mansoni
to be about 270 megabase pairs (haploid genome). Recent findings have shown that mobile genetic elements constitute significant proportions of the genomes of
S. mansoni and
S. japonicum. Much less information is available on the genome of the third major human schistosome,
S. haematobium. In order to investigate the possible evolutionary origins of the
S. mansoni long terminal repeat retrotransposons
Boudicca and
Sinbad, several genomes were searched by Southern blot for the presence of these retrotransposons. These included three species of schistosomes,
S. mansoni,
S. japonicum, and
S. haematobium, and three related platyhelminth genomes, the liver flukes
Fasciola hepatica
and
Fascioloides magna
and the planarian,
Dugesia dorotocephala
. In addition,
Homo sapiens
and three snail host genomes,
Biomphalaria glabrata
,
Oncomelania hupensis
, and
Bulinus truncatus
, were examined for possible indications of a horizontal origin for these retrotransposons. Southern hybridization analysis indicated that both Boudicca and Sinbad were present in the genome of
S. haematobium. Furthermore, low stringency Southern hybridization analyses suggested that a
Boudicca-like retrotransposon was present in the genome of
B. truncatus, the snail host of
S. haematobium.
