Question

1. Which of the following environmental factors is highly correlated with color vision in fish?

   		water temperature
   		water salinity
   		water depth
   		the coloration of prey

Answer 1

The correct option is (c) water depth.

In fishes, the rod and cone cells must adapt according to the depth of water they inhabit as they live in a different light environment. Water absorbs light and with increasing depth the amount of light also decreases. The absorption of light also depend on the wavelength of the light. Longer wavelength lights are absorbed less whereas light with shorter wavelengths are absorbed more.

Fish that live closer to the surface have more cone cells and less rod cells than fish that live deeper because visible light is more near the surface. Fishes live in photic zone have more rode whereas fishes in deep sea have minimal cone cells or may even absent and as a result they can not detect colors efficiently but they detect the variation in light.

Option (a) is incorrect because temperature does affect the rod cells of fish but the affect in the color vision of fish is not significant.

Option (b) is incorrect because salinity affects the penetrance of water as light penetrate more in less saline water. Saline water scatter more light and absorb less whereas less saline water absorb more and scatter less but this is significant in different salinity and is not significant in a single water ecosystem.

Option (d) is incorrect because coloration of fish is useful in camouflage, mating, and communication but it does not help or worsen the color vision of fish.