Rhythmicity of egg production by Heligmosomoides polygyrus in wild wood mice, Apodemus sylvaticus

The rhythmicity of egg production by Heligmosomoides polygyrus (Nematoda) in wild caught wood mice (Apodemus sylvaticus) was studied. Faecal production followed a 24 h cycle, with peaks at 0400 h and troughs at 1300-1900 h. The patterns in eggs per gram of faeces (EPG) and total eggs were similar to each other, though the former was more accentuated. Both of these followed a 24 h cycle, with peaks coinciding with troughs in faecal production and vice versa. Faecal weight was inversely correlated with EPG, but was not significantly correlated with total eggs. The pattern in EPG presumably reflected the effect of faecal production on the total eggs excreted in each 3 h period. The observed cycle in total eggs probably describes the pattern of egg production by the worm, although other factors, such as the host's intestinal rhythms, may contribute to this cycle.