Epidemiology and genetic variability of two species of nematodes (Heligmosomoides polygyrus and Syphacia stroma) of Apodemus spp.

The epidemiology and genetic variability of 2 parasitic nematodes Heligmoso moides polygyrus and Syphacia stroma of Apodemus spp. were investigated. Bo th are parasites of the same host, exhibit a direct life-cycle and are dioe cious. However, H. polygyrus has a diploid and S. stroma a haplodiploid mod e of reproduction. Haplodiploidy may lead to a more female biased sex ratio and reduced genetic variability. Levels of genetic diversity were analysed using both isoenzyme electrophoresis and RAPDs (random amplified polymorph ic DNA). Both parasites showed a female biased sex ratio with a stronger bi as for the haplodiploid parasite. Results showed significantly fewer geneti c polymorphisms as measured bq RAPDs for the haplodiploid parasite S. strom a in comparison with H. polygyrus. Despite the observed female biased sex r atio this could not be explained by a significant amount of inbreeding. Het erozygote deficiency for individual allozyme loci - which could indicate in breeding - was not found in either parasite species. Other features of the particular life-history of these species are likely to have an impact on th e sex ratio and genetic variability too.