Tetrachromacy class eventually lose two of their four cones. The normal explanation of tetrachromacy is that the organism's retina contains four types of higher-intensity light receptor (called cone cells in vertebrates as opposed to rod cells, which are lower intensity light receptors) with different absorption spectra. This means that the animal may see wavelengths beyond those of a typical human being's eyesight, and may be able to distinguish between colors that, to a normal human, appear to be identical. Species with tetrachromatic color vision may have an unknown physiological advantage over rival species. The goldfish ("Carassius auratus auratus") and zebrafish ("Danio
Light effects on circadian rhythm tract (RHT) the suprachiasmatic nucleus (SCN) of the hypothalamus receives light information from these ipRCGs. The ipRGCs serve a different function than rods and cones, even when isolated from the other components of the retina, ipRGCs maintain their photo-sensitivity and as a result can be sensitive to different ranges of the light spectrum. Additionally, ipRGC firing patterns may respond to light conditions as low as 1 lux whereas previous research indicated 2500 lux was required to suppress melatonin production. Circadian and other behavioral responses have shown to be more sensitive at lower wavelengths than the photopic luminous efficiency function which