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.