Tetrachromatic color vision in goldfish: evidence from color mixture experiments

Summary

Additive color mixture experiments were performed in the goldfish using a behavioral training technique in which the fish had to discriminate between two test fields.

• 1. When trained on monochromatic light of 570, 584, 599 or 608 nm, and tested against an additive mixture of 523 nm and 641 nm, the fish showed a “match” at certain mixture ratios. This was also the case when trained on 484, 490 or 495 nm, and tested against an additive mixture of 471 nm and 523 nm.

• 2. To match 404 nm, an additive mixture of 434 nm and 367 nm was necessary, whereas a mixture of 434 nm and 683 nm was always clearly discriminable.

• 3. For equality with the “white” light of a xenon-arc lamp, an additive mixture of 4 primary wavelengths was necessary and sufficient: 641, 523, 434 and 367 nm. This mixture was also equal to a mixture of 404 nm and 599 nm, and to a mixture of tungsten-“white” and UV.

• 4. The results can be qualitatively explained on the basis of the 4 cone types of the goldfish. For a quantitative description, cone sensitivity functions modified by inhibitory interactions have to be assumed. — Color vision in goldfish is tetrachromatic.