The influence of various species of digenean trematodes on rile in situ gro
wth rate of Littorina littorea (Gastropoda: Prosobranchia) from different h
abitats was investigated. The main results showed: (1) that infections eith
er reduced or had no significant effect on growth in comparison with uninfe
cted snails; (2) that the same type of infection could have a differential
effect on growth depending on the habitat/population from which the snails
originated. These findings are consistent with the life history hypothesis
expecting no or a stunting effect of trematode infections on the growth of
longer-lived snails, but do also emphasize that growth rates following trem
atode invasion can be significantly modified by environmental conditions, s
uch as, food availability.