WAVELENGTH DISCRIMINATION OF THE GOLDFISH IN THE ULTRAVIOLET SPECTRALRANGE

Wavelength discrimination ability of the goldfish was measured with a behavioural training technique in the UV spectral range. First, spectr al sensitivity was determined for the two fish to adjust the monochrom atic lights (between 334 and 450 nm) to equal subjective brightness. T he results of the wavelength discrimination experiment show that, inde pendent of which wavelength the fish were trained on, the relative cho ice frequency reached values above 70% only at wavelengths longer than 410 nm. Wavelength discrimination between 344 and 404 nm was not poss ible. Accordingly, the Delta lambda function increases steeply between 400 and 380 nm, with values between about 12 and 90 nm, respectively. Model computations indicate that the Delta lambda function cannot be explained on the basis of the cone sensitivity spectra. Instead, inhib itory interactions have to be assumed which suppress the short wavelen gth flanks of the short-, mid-, and long-wavelength sensitive cone typ es in the UV range.