Tributyltin (TBT) exposure experiments at 5 and 50 ng l−1 concentrations were carried out in the laboratory on female Hexaplex trunculus collected during the reproductive season from a site weakly-affected by imposex (12.1%). The imposex intensity estimated by the imposex incidence or frequency (I%), the average length of the vas deferens (VDL), the average length of female penis (FPL) and the vas deferens sequence index (VDSI) showed significant variation with TBT concentration. The number of spawning females decreased with TBT concentration. TBT had no effect on the number of egg-capsules laid per female nor on the number of eggs per capsule. The egg-capsules laid in the control and 5 ng TBT l−1 aquaria showed harder texture of the wall compared to those exposed to 50 ng TBT l−1. The mortality rate increased proportionally with TBT concentration and duration of exposure.
