Blue star vision

Question

For sake of argument, let's assume life did evolve on an earth like planet around a blue star. I have this idea that the animal equivalent life wouldn't have color vision so to let in less of the harsh light. Is this practical?

Answer 1

Advantages of seeing under a blue star: (1) The range of wavelengths available is wider, giving the potential for "more colors" -- for any given chemistry more interesting transitions occur in the area with the bulk of the energy. (2) The dominant wavelength is shorter, allowing sharper imaging with diffraction-limited optics. A smaller eye can see better than under a yellow sun.

Disadvantages of seeing under a blue star: There are more photons of high enough energy to disrupt the chemistry of your eyes (and skin...); under a hot enough star, the bulk of the energy (which you'd like to use for vision) may be in this category, so you probably don't want a pigment that just absorbs the high-energy photons and converts them to heat, since you're losing the chance to see them.

There's a lot of ways to build a system that can keep (some of) the advantages here while avoiding the disadvantages. One approach, as you mention, might be to give up on (most) color vision. Focus on resolution -- tightly packed rod-equivalent cells, sensitive to the peak frequency (or the peak frequency that does not destroy them). Then, evolve a dichroic filter by layering many nacreous layers on top of each other, reflecting anything that's not tightly at this frequency -- you have plenty of light, after all. If you'd like to see at night as well, put this filter on an eye lid so it can be retracted indoors and in safe conditions -- and even scatter in a few cone-equivalent cells for when the lid is up as well.

Or, don't give up on color. Have cells that are sensitive to specifically chosen wavelengths. Don't try to keep them alive on the brightest day -- instead, squint effectively. Either narrow the aperture, put a neutral density filter over it (again, on an eyelid if you want to be adaptable), or both. Occasionally you'll get a bad reflection and lose some eye cells, so rather than making them bulletproof, just have them be replaced quickly when damaged. Healing is a thing.

In summary, I think you can justify giving up on color vision in this world, but I don't think it's by any means necessary. If your organisms are able to stand the outdoor sun on their skin/outer surface (which poses its own challenges), then bringing in an acceptable amount of light and processing it is a very likely ability.

Answer 2

Evolution will find a way: on our planet there are animals who are blind because they don't have a use for vision, living in a very dark environment (moles, cave dwellers, etc.) and there are animals who can see in the harsh light of deserts, both hot and cold.

There is no reason to doubt that, if life can develop under a blue star, it won't also adapt to have vision under its light.