Single and multiple visual pigments in deep-sea fishes

The visual pigments in the retinal rods of 17 species of deep-sea fish were examined by microspectrophotometry or visual pigment extract spectrophotometry. In 15 species single visual pigments were found with peak sensitivities between 470 and 490 nm, typical of deep-sea fishes. However, in one species,Stylephorons cordatus, two visual pigments were found with λ values at 470 and 481 nm. In another species,Scopelarchus analis, three visual pigments were found with mean λ values of 444, 479 and 505 nm. The short-wave pigment of this species was found both in main and accessory retinae. It was present both in single rods and in outer segments which had the most long-wave sensitive pigment in their distal parts. It is argued that these two-pigment rods are in the process of changing their visual pigment from a ‘juvenile’ VP505 pigment to an ‘adult’ VP444 pigment. The VP479 was found only as a single pigment in rods in the accessory retina.