Why is common salt deadly to a gastropod mollusc?
The mollusc turns into “ooze” because a “diffusional gradient” (concentration difference) exsists between the liquid inside the mollusc and the salt outside of the mollusc. In most natural processes when a diffusional gradient is present, the solution seeks a state of equilibrium, meaning that the concentrations on the inside and the outside should be the same. The concentration of salt inside the mollusc is much less than the concentration of the pure salt on the outside of the mollusc. The cell membranes of the mollusc are designed to keep the nutrients and minerals inside but can pass water through the membranes. So the water inside of the mollusc passes through the cell membranes of the mollusc and tries to dilute the salt concentration on the outside of the mollusc. The movement of the water from the inside of the mollusc to the outside dehydrates the mollusc and the dehydration turns the mollusc into ooze.
