Trichromacy not very intense yellowish light would produce a stronger response from M cones than from other cones. Thus trichromatic color vision is accomplished by using combinations of cell responses. It is estimated that the average human can distinguish up to seven million different colors. Trichromacy Trichromacy or trichromatism is the possessing of three independent channels for conveying color information, derived from the three different types of cone cells in the eye. Organisms with trichromacy are called trichromats. The normal explanation of trichromacy is that the organism's retina contains three types of color receptors (called cone cells in vertebrates) with different
Three-spined stickleback then a stickleback's condition-factor (i.e. its ability to flee) determines how closely it approaches the predator rather than the stickleback's size. Both the strategy and reaction to different-sized partners seem to be dependent on whether the partner cooperates or defects. Sticklebacks have four colour photoreceptor cells in their retina, making them potentially tetrachromatic. They are capable of perceiving ultraviolet wavelengths of light invisible to the human eye and use such wavelengths in their normal behavioural repertoire. The three-spined stickleback is a known intermediate host for the hermaphroditic parasite "Schistocephalus solidus", a tapeworm of fish and fish-eating birds. Three-spined sticklebacks have