INTERSPECIFIC STIMULATION OF PARTHENOGENESIS IN SCHISTOSOMA-INTERCALATUM AND SCHISTOSOMA-MANSONI

Experimental studies of mating behaviour of Schistosoma intercalatum a nd Schistosoma mansoni in mixed infections in mice showed that in simu ltaneous infections, without the possibility of choice of mate, hetero logous pairing occurs readily. The paired females reach sexual maturit y, are inseminated and lay parthenogenetic eggs. Miracidia originating from the S. mansoni male x S. intercalatum female are non infective t o either Biomphalaria glabrata or Bulinus forskalii, whereas those fro m the reverse cross show a very low infectivity to only B. glabrata. T he resulting haploid male cercariae also show a very low infectivity t o mice (1.1%) and consequently only a very small number of adult worms develop. It appears from this study, on chromosomal and electrophoret ic evidence, that generative (haploid) parthenogenesis occurs in S. ma nsoni females paired with S. intercalatum males.