AGE-RELATED-CHANGES IN THE VISUAL PIGMENTS OF THE WHITE STURGEON (ACIPENSER-TRANSMONTANUS)

Using in situ microspectrophotometry, the spectral absorbance characte ristics of the photoreceptors in the retinas of larval, juvenile, and adult white sturgeon (Acipenser transmontanus) were determined. The ad ult has one type of rod, containing a visual pigment with maximum spec tral absorbance (lambda(max)) near 540 nm. There are three types of co nes, morphologically identical but distinguished from one another by c ontaining either a blue-sensitive (lambda(max) 464 nm), green-sensitiv e (lambda(max) 531 nm), or red-sensitive (lambda(max) 605 nm) visual p igment. Juvenile sturgeon have visual pigments similar to those of the adult. However, no evidence could be found for the presence of either blue-sensitive or red-sensitive cones in larval white sturgeon throug h the age of 10 weeks. Larval sturgeon up to about 10 weeks yielded on ly green-sensitive rods and cones. The absence of red-sensitive cones in the larvae, and their presence in older fish, was confirmed by the use of 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, a fluoresce nt substance that binds selectively to photoreceptors sensitive to lon g-wavelength light. Regardless of age, all visual pigments are based o n vitamin A2. Also regardless of age, white sturgeon retinas yielded n o evidence for the presence of photoreceptors sensitive to ultraviolet light.