The glochidium (plural glochidia) is a special microscopic larval stage of larger freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels. This larval form has hooks, which enable it to attach itself to fish (for example to the gills of a fish host species) for a period of time before it detaches and falls to the substrate and takes on the typical form of a juvenile mussel. Since a fish is active and fr… (More on Glochidium)