PHOTORECEPTOR MORPHOLOGY AND VISUAL PIGMENT CONTENT IN THE PINEAL ORGAN AND IN THE RETINA OF JUVENILE AND ADULT TROUT, SALMO-IRIDEUS

We performed microspectrophotometric measurements on isolated retinal and pineal photoreceptors of the trout Salmo irideus. Retinal rods con tain a visual pigment with lambda(max) at 512 nm. In adult trout the r etinal cone system consists of single and double cones with pigments h aving peaks at 453 nm (single cones and one member of double cones), 5 30 nm (single cones and one member of double cones) and 598 nm (one me mber of double cones). Juvenile fish possess an additional type of sin gle cone absorbing maximally at 400 nm. Scanning electron microscopy a nalysis of the cone mosaic shows a square pattern of double cones with a central single cone and corner single cones in yearling trout, and a similar pattern without corner single cones in two-year-old trout. O ur data on the pineal organ reveal two different kinds of cells showin g two distinct types of pigments, the former having its lambda(max) at 463 nm and the latter with its maximum at 561 nm.