Dj. Coughlin et Cw. Hawryshyn, THE CONTRIBUTION OF ULTRAVIOLET AND SHORT-WAVELENGTH SENSITIVE CONE MECHANISMS TO COLOR-VISION IN RAINBOW-TROUT, Brain, behavior and evolution, 43(4-5), 1994, pp. 219-232
Color vision in rainbow trout was studied by characterizing the spectr
al sensitivity of single units in three areas of visual processing: op
tic nerve; optic tectum; and torus semicircularis. Sensitivity to medi
um wavelength stimuli was a common feature of all single units examine
d. Additionally, long wavelength sensitivity was found in all units th
at were not medium wavelength-only or monophasic. Ultraviolet and shor
t-wavelength sensitivity was common in small, juvenile trout, with ult
raviolet sensitive units found in the optic nerve and torus, and short
wavelength sensitivity found in the optic nerve and tectum. The short
er wavelength inputs were excitatory and, if found in the same unit, s
ynergistic. The most common type of unit in the trout tectum and optic
nerve is trichromatic, with ON inputs from the long and short cone me
chanisms and an OFF input from the medium mechanism. In contrast, gold
fish color vision is dominated by L and M opponent units without S inp
ut. The segregation of ultraviolet sensitivity in the torus but not in
the tectum relates to functional differences of these two areas. Whil
e the tectum serves the function of wavelength discrimination, ultravi
olet inputs to the torus may contribute to prey detection and orientat
ion.