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It is reasonably well known that many species, such as bees and some types of birds as examples can see into the ultraviolet (UV). How is the structure of their eye different to humans to allow this?

Also, how are they shielded from some of the harmful effects of ocular UV exposure?

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Firstly most UV perceiving organisms only perceive far UV (~300-400nm) which is less damaging. There are different opsins, which get activated by different wavelengths. Like other light UV is perceived by opsins sensitive to UV wavelength [ref].

I am not sure about this but opsin sensitivity to UV must be high so that low irradiation is sufficient for perception and excess is filtered off. UV filter mechanism in reported for human and squirrel eye; mostly uses kynurenine derivaties. May be similar mechanism is present in other organisms too.

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    $\begingroup$ Thank you for this - I was not sure of the terminology involved - but I can now find research about the UV sensitivity to opsin. $\endgroup$ – user3795 Jun 17 '13 at 9:28
  • $\begingroup$ Your link [2] appears broken. $\endgroup$ – Ruslan Oct 24 '18 at 16:08
  • $\begingroup$ @Ruslan removed the broken link. The other reference explains the idea, I hope. $\endgroup$ – WYSIWYG Oct 29 '18 at 16:37
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The relevant structure of the eye only differs in one way, the types of cones present, different types of cones contain different opsins (light sensitive pigments). Reptiles and birds have 4 cone types, Mammals have 2 (primates have 3). Early mammals lost two of these as modern mammals are descended from early mammals who were nocturnal, one was the one that responds to UV light. Modern mammals as their descendants are stuck with this reduction since the genes to make those other cones is no longer present. Primates evolved a third cone, (a mutant variant of one of the two they had before) Primates did this because many a frugivores and color is excellent for determining when fruit is ripe.

enter image description here

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  • $\begingroup$ Your answer doesn't answer the question. Further, it seems a duplicate of this answer -1 $\endgroup$ – AliceD Jul 17 '18 at 15:57
  • $\begingroup$ Also note that links can grow cold; citations to journals papers + web link are best, as these can always be found back in any university library or other search engine $\endgroup$ – AliceD Jul 17 '18 at 15:58
  • $\begingroup$ @alice I did add the sources to the other answer, and this is different than the other answer, it does not require much change because the question has fundamentally the same answer. $\endgroup$ – John Jul 17 '18 at 16:00
  • $\begingroup$ yes I'm sorry about the sources; I saw that now; I upvoted the other answer. $\endgroup$ – AliceD Jul 17 '18 at 16:01

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