[Dose as the determining factor for the size of the parasite population in the Muellerius capillaris/Cernuella cespitum arigonis system (Nematoda, Protostrongylidae/Mollusca, Stylommatophora].

Ten lots, each one made up of 40 specimens of the snail Cernuella (Xeromagna) cespitum arigonis, were infected with L1 of the nematode Muellerius capillaris, at dosages ranging from 50 up to 1,000 L1/mollusc, in order to determine the influence of the infecting dose on the invasion and further development of the parasite population. Mathematical calculations are based on a basic model of a growing population. During the invasion phase a densith dependence on the number of available larvae was demonstrated, the process being adjusted to a binomial distribution and, secondly, to a Poisson type. The step from L1 to L2 was also density-dependent, and also the development from L2 to L3.