I don't know of any research that has been done on the ability of mollusks to see in the UV range. Seems like it would be a difficult thing to measure. Many other invertebrates, especially insects, can do so. However, many of the mollusks which have fluorescent compounds in their shells live at depths far beyond the penetration of UV radiation. Therefore, they never fluoresce in their natural habitat, even though they have the potential to do so. Others, like the fluorescent cowries, may live in shallow water, but tend to be nocturnal, hiding in dark recesses during daylight hours. So it would seem that their potential to fluoresce would likewise be of little value to them. Therefore, I think that fluorescence is simply an incidental characteristic of compounds which are present for some other reason. Paul M.