Effects of Pseudobranchectomy on Visual Pigment Density and Ocular PO2 in Atlantic Salmon, Salmo salar

Abstract

Bilateral pseudobranchectomy (B.P.) of Atlantic salmon, Salmo salar, resulted in a progressive loss of visual pigment and a marked decrease in ocular PO2 near the retina. B.P. fish were dark and blind within a few hours of pseudobranchectomy. Unilateral pseudobranchectomy (U.P.) did not have a similar effect on ocular PO2 or visual pigment density in either the ipsilateral or the contralateral eye. U.P. fish did not become dark or blind. An interconnection exists between the right and left ophthalmic arteries permitting an intact pseudobranch to supply blood to the contralateral eye whose pseudobranch has been removed. Although intramuscular injection of acetazolamide caused an initial decrease in amount of visual pigment, body darkening, and blindness, these effects were not permanent. Acetazolamide also caused a marked decrease in ocular PO2 similar to that in B.P. fish. In control fish, dorsal aortic blood and ocular PO2 values were dependent upon an adequate irrigation of the gills. Key words: salmonid, Salmo, pseudobranch, oxygen tension, eye, visual pigment