Mating in the nematode parasite Strongyloides ratti: proof of genetic exchange

Strongyloides, a parasitic nematode, has a complex life cycle that represents a transition between free-living and purely parasitic ways of life. By using minisatellite DNA fingerprinting, we have detected a large number of polymorphic loci in cloned lines of S. ratti. In controlled crosses between free-living adults of S. ratti, we show that genetic exchange, consistent with normal sexual reproduction, occurs. This is in contrast to earlier cytological studies which claimed that reproduction in this organism was by pseudogamy, and thus that inheritance was maternal only.