© 1989 by The Society for Integrative and Comparative Biology
Determinants of Compatibility in Mollusc-Trematode Parasitism1
Department of Zoology, Oregon State University Corvallis, Oregon 97331
Department of Zoology, University of Oklahoma Norman, Oklahoma 73019
The low prevalence of schistosome-infected snails in hyperendemic habitats, and the demonstrated ability of snails, in general, to recognize and eliminate a myriad of foreign substances and/or infectious agents, lead to the postulate that host resistance to larval trematodes must be considered the "rule," while susceptibility (compatibility) represents an exceptional occurrence. In this review, we discuss a variety of possible mechanisms by which compatibility between trematodes and their molluscan host might be attained. Included among these are parasite mimicry of snail host molecules, prevention of opsonization, interference with hemocyte behavior or differential stimulation of hemocyte metabolic processes. Evidence that compatibility is the result of the ability of larvae to resist toxic host molecules or to acquire protective host components on their surface membranes is lacking. Clearly, there are multiple variables of both host and parasite origin which ultimately determine compatibility. Careful identification and dissection of these variables will be required before we achieve a complete understanding of how compatible snail-trematode associations are established and maintained.