Evidence for periosteocytic osteolysis in vertebrae of Atlantic salmon, Salmo salar (Salmonidae, Teleostei), during its anadromous migration.

A study of the size of osteocytic lacunae has been undertaken on microradio graphs of vertebral skeleton of Atlantic salmon (Salmo salar L.) at differe nt stages of its life cycle. A significant in crease of the mean size of pe riosteocytic lacunae in adult salmons (46 mum(2)) compared to parr and smol ts (29.3 mum(2)) attests the process of periosteocytic osteolysis, which is responsible for the release of calcium. Such osteolysis increases signific antly in salmons at the end of their migration compared to salmons at the b eginning of their anadromous migration (61-67 mum(2)). We have therefore ev idence for three types of bone resorption in salmon skeleton: osteoclasy, h alastasy and periosteocytic osteolysis.