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why different eyes?: |
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peterh Member Joined: 28 Jan 2008 No. of posts: 12  View other posts by peterh |
Posted: 10 Feb 2008
beauty hides in all things, its just different eyes see it in different ways. |
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tim hamlett Senior Member Joined: 17 Dec 2006 No. of posts: 572  View other posts by tim hamlett |
Posted: 10 Feb 2008 don't know about the shape of the pupil but i think most reptiles have excellent colour vision - better than ours i think. cheers tim |
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Caleb Forum Coordinator Joined: 17 Feb 2003 No. of posts: 448  View other posts by Caleb |
Posted: 11 Feb 2008 This paper suggests that slit pupils are associated with lenses which have concentric zones with different focal lengths. Apparently these concentric zones help prevent colour blurring at low light levels, and a slit pupil can keep all these zones active at higher light levels. A round pupil would obscure the outer focus zones as it narrowed down at high light levels. So a slit pupil would be expected in an animal that needs to be able to see in low and high light levels. Not sure how this applies to adders & grass snakes, though... all vipers have slit pupils, don't they? Maybe vipers developed from an ancestor that needed to see at night (or underground), as well as in the day... |
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Vicar Senior Member Joined: 02 Sep 2004 No. of posts: 1181 View other posts by Vicar |
Posted: 11 Feb 2008 I don't know the answer to this one...but some thoughts about the physics involved... Slit pupils optimise the capture of images from multi-focal lenses. These multi-focal lenses have various focal points attuned to specific wavelengths of light (from what I've read). One of these 'colours' could be in the near infra-red, which would help with night vision. A lot of vipers are nocturnal ambush snakes, so the adder could be a diurnal evolution from this family. We know that on warm nights the adder does hunt at night, so maybe the diurnal evolution allowed it to occupy cooler climes? (as we know the adder has the coolest range of any snake). One last thought...near infra-red vision could be used in conjunction with heat-sensing pits, the pits being used to cue the eyesight for a more accurate strike. I know some constrictors have vertically slit pupils, but can't remember if those are the ones with pits too. None of this is gospel, just speculation. If grass snakes hunt at night (?) then that blows this theory out of the water, as in my experience, the grass snake has better diurnal vision than the adder. Steve Langham - Chairman 
Surrey Amphibian & Reptile Group (SARG). |
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peterh Member Joined: 28 Jan 2008 No. of posts: 12 View other posts by peterh |
Posted: 11 Feb 2008
beauty hides in all things, its just different eyes see it in different ways. |
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- why different eyes? |
thanks . pete.