STRUCTURE OF LEPTORHYNCHOIDES-THECATUS AND POMPHORHYNCHUS-BULBOCOLLI (ACANTHOCEPHALA) EGGS IN HABITAT PARTITIONING AND TRANSMISSION

The role of egg structure in transmission and habitat use of Leptorhyn choides thecatus and Pomphorhynchus bulbocolli (Acanthocephala) was in vestigated. During storage in tap water at 4 C, the outer membrane of L. thecatus eggs was lost, releasing ribbonlike filaments of the fibri llar coat. After similar storage, the outer membrane and fibrillar coa t of P. bulbocolli eggs remained intact. Eggs of L. thecatus entangled in algae, whereas those of P. bulbocolli settled to the substratum. L eptorhynchoides thecatus infections in amphipod intermediate hosts wer e significantly more prevalent and dense when eggs were allowed to ent angle than when they were not. Prevalence and relative density of P. b ulbocolli infections in amphipods were not significantly different bet ween trials in which entanglement was possible and those in which it w as not. These results indicate that although the same species of amphi pod, Hyalella azteca, is the intermediate host for both acanthocephala n species, mechanisms of transmission differ. Differences in fibrillar coats result in segregation of the environment in a manner that affec ts transmission and occurrence in intermediate hosts.