Fecundity of Lymnaea stagnalis individuals in restricted mating roles during five days. Fecundity during five days for Lymnaea stagnalis individuals restricted to experimentally allowed mating roles. "Control" and "Sham" treatments include reciprocally mating focals ("Reciprocal copulants"), whereas the "Receive" and "Donate" treatment' focals are restricted to mating as a recipient and as a donor, respectively ("Single sex copulants"). In the "Operated" treatment focals do not mate at all ("Non-copulants"). The symbols depicted in the bars denote the imposed mating role(s) of the focal individuals in the different treatments. The bars indicate mean ± 1 SE. Tukey post-hoc results are shown above the bars.