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Population biology of Bothriocephalus rarus Thomas (1937) in the red-spotted newt, Notophthalmus viridescens Raf

SUMMARY The distribution and abundance of the cestode Bothriocephalus rarus infecting red-spotted newts, Notophthalmus viridescens, were studied for over 1 year in an artificial pond in West Virginia, USA. Macrocyclops ater and Mesocyclops edax were found to harbour B. rarus procercoids experimentally, and M. ater was confirmed as a natural intermediate host for this cestode. The recruitment of B. rarus by newts coincided with the peak density of M. ater, indicating that B. rarus may have adapted itself to the copepod life-cycle to increase the probability of successful parasite transmission. Infection was more frequent and of higher intensity in larval newts. The observed frequency distribution of cestodes in all segments of the newt population closely fits the negative binomial. The data indicated seasonal cycles in population structure, intensity of infection, maturation and reproduction. Recruitment of worms by adult newts occurred in June, July and August, at the time when the density of adult worms decreased.