INFRAPOPULATION DYNAMICS OF HALIPEGUS-OCCIDUALIS AND HALIPEGUS-ECCENTRICUS (DIGENEA, HEMIURIDAE) - TEMPORAL CHANGES WITHIN INDIVIDUAL HOSTS

Individual infrapopulations of Halipegus occidualis and Halipegus ecce ntricus (Hemiuridae) in the buccal cavities of their amphibian host (R ana clamitans) were monitored for changes over time. Rates and pattern s of parasite maturation, recruitment, and loss were estimated, and th e probabilities of infection for definitive hosts in this system were calculated. Although variable, the time required for maturation of imm ature worms (once in the buccal cavity) was as little as 1 wk. Relativ ely rapid losses of worms from individual infrapopulations were observ ed, although this did not appear to inhibit additional recruitment of these trematodes. Also, it was clear that these species overwintered w ithin their amphibian hosts. There was no statistical difference among the 3 sampling years in the probability of acquiring an initial or a subsequent infection with either parasite. However, we suggest that fr ogs with an existing infrapopulation may have a greater probability of adding worms if those hosts are within certain foci of infection with in the pond. The probability of frogs becoming infected in this system increased in late spring and peaked in midsummer. By examining the te mporal changes within individual infrapopulations, it is clear that dy namic changes in infrapopulation size and composition may occur, sugge sting that rates of trematode transmission may be greater than previou sly estimated.