Photopic vision in eels: evidences of color discrimination

Several classes of second-order retinal neurons have been studied electrophysiologically in European eel (Anguilla anguilla) from two different localities, Lake Seliger in Russia and the coastal waters of the Adriatic Sea in Montenegro. The majority of L-horizontal cells (68 explored) had both rod and cone inputs, an uncommon phenomenon among teleosts. Pronounced color-opponent properties, often taken as pointing to the capacity of color vision, were identified in one amacrine cell, apparently of the "blue/yellow" (or "blue/green") type. Microspectrophotometric measurements revealed two different spectral classes of cones with absorption maxima at about 525 and 434 nm. The existence of green-sensitive and blue-sensitive cone units was thus revealed by both electrophysiological and microspectrophotometric techniques.