On 18/11/2013 3:23 PM, Peter Shute wrote:
So Owlet-nightjars don't have this Tapetum Lucidum?
I don't know about Owlet-nightjars. The fainter red colour would suggest
not, (Although some animals have a Tapetum Lucidum layer that gives a
bright reddish shine) but that seems a bit strange in a bird that is
supposed to be nocturnal. Perhaps most of its activity is crepuscular,
and there has been less selective pressure to develop or maintain the
structure. Alternatively perhaps the evolutionary line lost or didn't
gain the ability to produce the structure in the past. The
Owlet-nightjars are a group which appears to have evolved rather early
on in the evolutionary history of birds. They are certainly not closely
related to the owls or nightjars; groups which do appear to have a
Tapetum Lucidum layer.
Phylogeny of the owlet-nightjars (Aves: Aegothelidae) based on
mitochondrial DNA sequence
John P. Dumbacher, Thane K. Pratt, and Robert C. Fleischer
Molecular Phylogenetics and Evolution 29 (2003) 540–549
at
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.61.2950&rep=rep1&type=pdf
Andrew
I assume putting the torch closer to your eyes to help see the fainter shine
uses the same principal as moving a camera flash further from the lens to
reduce red-eye.
Peter Shute
Sent from my iPad
On 18 Nov 2013, at 4:55 pm, "Andrew Hobbs" <> wrote:
The colour of the eye reflection from the Tapetum Lucidum depends upon
the properties of the crystals in the layer. It can vary more or less
across the full visible spectrum. However in animals without that layer
the reflection is always red. The red colour is mainly due to the
haemoglobin in the blood vessels at the back of the eye. (This is the
basis for the red eye effect in people. We don't have a Tapetum Lucidum.
--
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Andrew Hobbs
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