Degenerative processes in the marginal retina of the tench (Tinca tinca)

By cryolesion of the scleral-corneal perimeter of the eye of a teleost we eliminated both the marginal growth ring and the immature portions adjacent to the neural retina. Electron microscopy revealed necrotic destruction of the whole of the germinative zone and a large number of apoptotic cells in neighbouring zones. In the degenerative processes that follow the lesion, at least three types of cells are involved: microglial cells, pigmentary cells and extravascular heterophilic granulocytes. Both microglia and the pigmentary cells act as phagocytes and participate in the elimination of debris from the lesioned area. Heterophilic granulocytes probably collaborate in the modification of the environment for the subsequent regeneration. During the degenerative processes after the lesion, all three cell types participate in the transformation of the damaged retinal zone into a favourable medium for later regeneration of the neural tissue.