Visual pigments in the early life stages of Pacific northwest marine fishes

Microspectrophotometry was used to measure the visual pigments in the rods and cones of 22 species of marine fish larvae netted from the surface water s off Friday Harbor Laboratories, Washington, USA. 13 species had rods, 12 of which contained visual pigments with a wavelength of maximum absorbance near 500 nm, while one, the sand lance (Ammodytes hexapterus), had its abso rbance maximum at 482 nm. The 22 species of fish larvae possessed varied co mbinations of single, double and twin cones, ranging in peak absorbance fro m 353 nm to 584 nm. Of these, green-sensitive single cones were present in 20 of the 22 species, and were the dominant cone type. Double and twin cone s were present in 13 of the species. Most common were identical green-sensi tive (twin) cones (in 11 species). Green/yellow-sensitive double cones occu rred in four species. In a single instance (Hemilepidotus hemilepidotus) tw in blue-sensitive, twin green-sensitive and double blue/yellow-sensitive co nes were recorded. Of particular interest was the finding that 18 of the sp ecies had ultraviolet- and/or violet-absorbing single cones. It has been suggested that short-wavelength photosensitivity may be benefic ial for planktivory by extending the spectral range over which vision can o ccur. The high percentage (82 %) of ultraviolet and violet visual pigments in Pacific northwest fish larvae supports the prediction that short-wavelen gth sensitivity may be common in marine fish larvae.