Studies on the helminth parasites of small mammals, with particular reference to the ecology and physiology nematode Nematospiroides dubius, Baylis 1926

Abstract

A study of the monthly incidence and intensity of infection of Apodemus sylvaticus and Clethrionomys glareolus with selected intestinal helminths has been made. The majority of the variation in these two factors was shown to he due to differences in the age and sex ratio of the host populations throughout the year. Multiple regression and correlation analyses were used to assess the effect of independent environmental variables on the incidence and intensity of infection. A competitive interaction was found to occur between the trichostrongylid nematode Nematospiroides dubius and the oxyurid Syphacia stroma in the small intestine of Apodemus sylvaticus, though such an interaction did not lead to the total exclusion of either species. The distribution of N. dubius in the small intestine of laboratory mice was found to Be highly aggregated with respect to Both the intestine and the worm population; this was thought to occur in response to a gradient in oxygen tension along the mouse gut. Growth curves of male and female N. dubius in male and female mice were typically sigmoid and the daily growth rates for each sex of worm were the same in Both sexes of mice. The growth of the free-living stages was negative after infectivity had been reached. The respiration rates of male and female N. dubius increased with age, whereas those of the free-living stages decreased after infectivity was reached. The size/metabolism relationship for free-living stages N. dubius indicated a slow-down in metabolism as soon as infectivity was reached; this is likely to be of adaptive significance to a non-feeding stage. The size/metabolism relationship of both male and female parasitic stages indicated that aerobic metabolism may be important in vivo.