HYBRID VIGOR AGAINST PARASITES IN INTERSPECIFIC CROSSES BETWEEN 2 MICE SPECIES

The resistance and susceptibility to the intestinal pinworm Aspiculuris tetraptera, a natural parasite of the house mouse Mus musculus, is experimentally analysed using both the F-1 from wild-type mice of the two subspecies (M. m. domesticus and M. m. musculus) and the F-1 from different laboratory inbred mice. The results show that: (i) the F-1 from wild-type mice harbour a lower parasite load than the parental mice, suggesting a phenomenon of hybrid vigour; and (ii) the F-1 from inbred mice harbour parasite loads similar to the resistant parent, suggesting that resistance is inherited as a dominant feature in these laboratory mice. This analysis supports the hypothesis that recombinations occurring between the two mouse genomes (i.e. M. m. domesticus and M. m. musculus) are responsible for the hybrid dysgenesis observed in the natural hybrid zone between the two mice subspecies.