Seasonal population changes in Rhabdias ranae Walton, 1929 (Nematoda: Rhabdiasidae) in Rana sylvatica of Ontario

Abstract

Rana sylvatica collected monthly from April to October of 1976 and 1977 in a marsh near Guelph, Ontario, were examined for the presence of Rhabdias ranae. Prevalence and intensity of infections were lowest in summer and highest in spring and early fall of both years. Many nematodes collected in late summer and early fall were subadults found in the body cavity of frogs and, therefore, this period was important for transmission. No nematodes were recovered from the body cavity of frogs in spring and few were recovered from this location in late fall. Seasonal fluctuations in size of worms indicates there was a single annual cycle of growth of worms and that there was only one or possibly two generations in frogs each year. The data indicate transmission began later in the spring of 1976 than 1977 and ceased later in the fall of 1976 than 1977. Young-of-the-year frogs acquired infections in the same summer they transformed from tadpoles. Survival of the species in Ontario is dependent on adult nematodes overwintering in frogs.