THE RELATIVE IMPORTANCE OF BLADDER VERSUS NEOTENIC STAGES OF POLYSTOMA-MARMORATI AND POLYSTOMA-UMTHAKATHI IN NATURAL FROG POPULATIONS IN SOUTH-AFRICA

Infection levels of Polystoma marmorati (Polystomatidae: Monogenea) in the painted reed frog, Hyperolius marmoratus, and P. umthakathi in th e kloof frog, Natalobatrachus bonebergi, were studied under natural co nditions. The recorded prevalence for P. marmorati was generally high in adult frogs and low in tadpoles. In the case of P. umthakathi, the opposite was found with a low prevalence in adult frogs and a very hig h prevalence in tadpoles. Based on these findings, the hypothesis is p resented that for P. marmorati the neotenic stage does not play a dete rmining role and the population is maintained by bladder parasites. Fo r P. umthakathi the neotenic stage appears to be more important than t he bladder parasite and the population can probably survive without an y significant contribution from bladder parasites.