Evolution of sensory detection

Pythagorean

If you google uoregon fovea fractal, you'll find Richard Taylor's work in fractal shaped sensory replacement. On my iPhone at the moment so linking is a pain.

fuzzyfelt

Shall do, thanks, Pythagorean.

Ken Natton

Sorry for the delay in replying fuzzyfelt, I am working away from home at the moment and I have limited opportunity to respond. I’m afraid I cannot provide the direct links that you want, but I am certain that the formal scientific papers do exist. My source is just a particular edition of popular science program here in the UK called Horizon. But that edition of Horizon did refer to actual serious research which is what gives me the confidence that the papers do exist. I have had a little hunt on the BBC website and managed to find a link to the actual programme. That is the best I can do for you.


http://www.bbc.co.uk/programmes/b00vhw1d


Hi DavidMcC. I would not presume to be able to question whether Dawkins is right or wrong on any particular point. I have commented elsewhere on his style about which I am not unreservedly praising. But for me, at his best, he is a very fascinating writer. I shall check out the link you provided, and respond if I have any particular thoughts about it.

DavidMcC

Ken, I agree that Dawkins is a "fascinating writer". Indeed, it was his earlier books on evolution that inspired me to think a lot about the subject in the first place. However, I tdoubt that science can progress if no-one dares challenge the "received wisdom" on particuar subjects.
I include here some useful references to the detailed biological studies that have been carried out in the last decade-plus.
http://www.photobiology.info/Rozanowska.html
Although this study does not deal with photochemical damage to the opsins themselves, it does illustrate the general problem, particularly of oxidative optical damage to organic dye molecules. I cannot imagine that opsins are immune from this, as we would probably not otherwise have eyes that go to such trouble to renew them on a daily basis.

http://www.jneurosci.org/content/19/15/6267.fullAbout opsin transport in the connecting cilium, which is immediately adjacent to the region of the photoreceptor cell outer segment (ROS) where new opsin discs are growing.
These are destined to be literally "chewed off" by the attendant retinal pigment epithelial (RPE) cell when they have reached the outer end of the outer segment, as illustrated here:
http://webvision.med.utah.edu/imageswv/photphag.jpeg
What this seems to imply is that the opsin molecules are so tightly bound in the disc that
they cannot be replaced in situ. Therefore the only option is to dump an entire "cartridge" of them at one end, and make a new one at the other end, each day..

fuzzyfelt

No matter about the delay, Ken Natton, thank you for your response.