Abstract
Competition between three Cuban lymnaeid isolates (one of Fossaria cubensis and two of Pseudosuccinea columella resistant and susceptible to Fasciola hepatica miracidial infection) was assessed in order to study the interactions between these snails. Growth and fecundity were compared under laboratory conditions among the three isolates. Comparisons involved snails raised in the presence of a partner from the same or a different isolate. Both growth and fecundity were significantly different bewteen isolates. F. cubensis raised in the presence of resistant P. columella showed a diminished shell growth and fecundity compared to snails raised in the presence of susceptible P. columella or a conspecific partner (uniformly-paired). Susceptible P. columella increases its shell growth rate when snails are raised with either F. cubensis or resistant P. columella but its fecundity rate is not significantly altered; resistant P. columella does not seem to suffer any changes in growth or fecundity when snails are raised in the presence of any partner. The net reproduction rate of F. cubensis is reduced in snail raised with P. columella (either resistant or susceptible) compared to uniformly-paired snails. The net reproduction rate of P. columella (either resistant or susceptible) increases when snails are raised with F. cubensis compared to uniformly-paired snails. The presence of resistant P. columella increases the net reproduction rate of susceptible snails compared to uniformly-paired snails whereas resistant P. columella show a decreased net reproduction rate in the presence of susceptible snails. The results suggest that a chemical interaction takes place by means of excretory-secretory molecules produced by one or both species