As I squished a fruit fly between my fingers, the red eyes left a faint stain on my skin. And I wondered, why are their eyes such a bright red?
I recall in biology breeding flies with the white eye mutation, so it’s obviously not essential. But such a bright color makes them more vulnerable to predators which can see colors, so there must be some advantage that outweighs this risk.
I don’t know, but it could be:
[li]They don’t have a pigment at all and the red colour is simply the colour of some body fluid or other)[/li]Red objects absorb nearly all green light; unripe fruit is often green (i.e. their eyes are optimised for seeing green things)
Because they stay up late at night drinking banana daquiris!
(sorry dqa,I couldn’t resist:)
they dont all have red eyes. when i was at Uni i did a genetics coarse and we examined fruit flies eyes. some are scarlet, some vermillion, some white…i cant remember the other versions, i think some are yellow but i’m not certain. they are all genetic variations and some colours are recessive genes others are dominant - i think red is dominant and most are red.
“white, light red ( cn ), red ( + ), dark red ( ? )
and brown ( bw )”
these are common colours of the fruit flt * drosophila melanogastor *
[QUOTE]
*Originally posted by Mangetout *
[li]Red objects absorb nearly all green light; unripe fruit is often green (i.e. their eyes are optimised for seeing green things) **[/li][/QUOTE]
This makes sense. Am I correct that you actually meant optimised to see non-green things? Or that by green fruit showing up darkest, it would be easiest to see and thus avoid? I would lean toward the former.
dqa, if the eyes are red then red is being reflected so presumably they cant see red ,ie: it would be black. green would look green and blue would look blue. i dont know about this explaination though as many types of flies have red eyes, not just fruit flies.
I would think that if the red is on the outside of the eye, it would act as a filter. Thus, only red would get through to the compound retinae(? I’m a bit fuzzy on compound eye anatomy). Unripe green fruit, which reflects predominantly green light, would be very dark. Strawberries would be little affected. Mmmm…strawberries.
As we’ve both pointed out, it can’t be an essential feature since there are white and other variants. I had also thought about the reddish color of housefly eyes and other flies. Don’t have any nearby to check, and couldn’t find any good color pix to examine, but in line with Mangetout’s theory, it wouldn’t surprise me if houseflies had a more of a brownish color to their eyes.
Another thing worth considering is that in more industrialized areas, the rotten fruit is usually in a garbage can or the bottom of some opaque fruit storage container. So the eyes would be pretty much useless, except to fly towards the light when the container is disturbed.