GENETICS, SEX AND EXPOSURE - THE ECOLOGY OF HELIGMOSOMOIDES-POLYGYRUS (NEMATODA) IN THE WOOD MOUSE

Male Apodemus sylvaticus, had consistently higher nematode burdens than females exposed to the same number of parasite larvae. The difference was most pronounced in repeated infection. The characteristics of parasite survival and fecundity in primary infection are described. There was no evidence of density dependence. The population dynamics of repeated infection demonstrated a reduction in parasite survival proportional to the cumulative number of parasites with which the host had previously been infected. The most likely explanation for this exposure-dependent constraint on parasite population growth is acquired immunity. Variability in parasite population dynamics between individual wood mice was much greater in repeated infection than in primary infection, indicating that it is the result of heterogeneity in immunocompetence. The heterogeneity probably has a genetic basis. -from Authors