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Flower patterns

Insect Vision
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#1 DaveO

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Posted 14 December 2016 - 03:56

Here's an interesting review, together with good references which gives some idea of where the frontiers of insect vision lie at the moment:

More than colour attraction: behavioural functions of flower patterns
http://www.sciencedi...214574515001364

It looks like a good journal to keep an eye on

Dave

#2 Andrea B.

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Posted 14 December 2016 - 19:02

This is indeed an interesting paper, Dave.

It reminds us that insect vision is very much more complex than our simple photographic models can show.

I am not sure I would have represented the "bee colours" the way the authors did. But that has nothing to do with the conclusions of the paper. None of the human-visible models of bee colours is entirely satisfactory, of course. :)
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#3 DaveO

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Posted 19 December 2016 - 02:38

Andrea,
Our friend Adrian Horridge
http://adrian-horridge.org/

Has continued his tradition, as an eminent retired professor, of publishing controversial papers, with his latest (which has a direct download link on his web page above) paper entitled "Parallel Inputs to memory in bee colour vision". If you think you know about insect vision you should read this paper.

An earlier paper of his "How bees distinguish colours" also linked on his website, stated (in 2015) "We know very little about the UV channel" page 32.

Back to head bashing on that brick wall!

Dave

#4 Andrea B.

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Posted 19 December 2016 - 06:26

I enjoy Horridge's writing. The Introduction in the "Parallel Inputs" paper is wonderful. I read through about 1/3 of the paper. But it's tough going when one is not conversant with the finer details of vision research.

Near the end of that Introduction is the phrase "UV has never been seriously implicated in bee colour vision". We should remember that next time we are attempting to model bee vision in our UV photographs. :D
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#5 DaveO

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Posted 19 December 2016 - 09:22

I thought you would like that, there seem to be several schools of thought and he sums up the position quite clearly.

I note that the paper, ref 10, which found that UV inhibits the blue channel in bees was done in 1939. He shows quite clearly that you can only try to tell what is going in the bee brain, by testing their response to targets in a lab environment but that is only as good as the experimenters who do the interpretation. There's a cautionary tale there for me at least - what would a mere chemist know about all that.

He's an ex-pat Yorkshireman as well, I reckon we were born within about 20 miles, so you know who I back.

Dave

Edited by DaveO, 19 December 2016 - 09:23.


#6 Alaun

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Posted 19 December 2016 - 21:19

Dave, thanks for the link. The video with the interview is also worth to watch. I like, what he writes about bee vision, because it explains, what I had some how in mind in my post to Nicos statement about bee colors here: http://www.ultraviol...-bee-colours-i/

(?does this link work?)

Werner
Werner

#7 Andrea B.

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Posted 19 December 2016 - 21:34

(yes, that link works.) :)
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#8 DaveO

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Posted 20 December 2016 - 03:22

Here's a link to the 1939 paper by Mathilde Hertz
Hertz M (1939)
http://jeb.biologist.../content/16/1/1

which I found difficult to read and come to the conclusion that UV inhibits blue. In fact in the 1939 paper it was not stated, perhaps because it wasn't known then, that the bee had sensors for UV, blue and green.

I'm trying to work out what all this means. When we see a pattern on a flower petal in UV images we are really seeing areas of UV absorption to perhaps lead the insect towards the areas it should visit to achieve pollination of the flower. Perhaps the UV-dark areas are highly attractive to the insect but how can it detect absorption of UV in a very bright visible environment? Perhaps the UV sensor doesn't react to visible light by becoming over saturated as happens in our cameras unless we filter out the visible light with a Baader filter.

Dave

#9 Andrea B.

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Posted 20 December 2016 - 04:18

but how can it detect absorption of UV in a very bright visible environment?

If the insect colors are UV, blue & green, then a UV-absorbing subject would be reflecting both blue & green (cyan). [Unless, of course, the subject is pure black -- absorbs all of UV, blue and green.] So the insect is not detecting UV-absorption, per se. Instead it is detecting the complementary reflected cyan color.

That's also how human vision works. For example, we humans do not detect absorbed green. Instead we detect reflected red & blue (magenta), the complementary reflected color.

[If the insect UV does indeed inhibit blue, then my initial statement should be altered.]

In summary, the UV-camera and the insect do not see UV-absorbing areas in quite the same way. The UV-camera sees only UV, and so the camera records only the absorbtion and reflection of one "color", namely, UV. It is just an artifact of the UV passing through a Bayer filter that gives us the false colours -- which somewhat confuses the issue.

Well, I am probably just confusing the issue myself.......... :D




I dig myself deeper.
The UV-camera sees only UV. However if the UV-pass filter is wide enough, we could postulate that the UV-camera is receiving more than one UV-color. But we do not have proper UV-color filtration to separate those possible UV-colors. And we do not have a natural way to define UV-colors in the band from 300-400 nm like we do in any Visible band of 100 nm width. For example, the visible 500-600 nm band contains cyan, green, yellow and a bit of orange. It is certainly theoretically possible to create a Bayer-type filter which separates UV-colors. Wouldn't that be wonderful??

What I really really want to have is a wavelength detecting camera which is configurable. Like so I could assign 300 - 333nm to blue, 334-366 nm to green and 367-400 nm to red.
Andrea G. Blum
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#10 DaveO

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Posted 21 December 2016 - 02:17

Here's an interesting paper which actually contains some UV images

UV floral polymorphism
http://www.amjbot.or...6.full.pdf+html

and another on epidermal/conical cells

Epidermal cell types and UV patterns
http://ideaexchange....ch_projects/15/

Dave

Edited by DaveO, 21 December 2016 - 02:30.


#11 Andrea B.

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Posted 22 December 2016 - 01:12

That paper about floral polymorphism has really captured my interest. I've got examples of different patterns in the same species. So I think I'll write to the authors and show them a couple of my samples.

As for the 2nd paper, Bjørn and I also have some examples showing how epidermal cells affect UV reflection.

Naturally the examples we have of polymorphism and epidermal cell effects are simply photographic examples and have not been studied with regard to pollinators or eco-regions or any other context.
Andrea G. Blum
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#12 DaveO

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Posted 25 December 2016 - 01:11

Back in my student days, in the stone age, it would have taken me about 3 years to reach this Eureka moment. Search for Matthew H Koski and follow his publications for 2014 and 2016 and you will find some interesting nuggets. He points out in the 2016 paper "..products of the flavonoid biosynthetic pathway that protect vegetative tissues from UV-B irradiance, temperature, and/or drought stress also underlie UV-absorbing pigments in floral tissue..." In other words, the UV-absorbing pigments protect the vital parts of the plant (as I have seen with almost all anthers being UV-black) and the pollinators then learn to search for those parts to show the way to food rewards.

Here goes another of my signature Lead Balloons :rolleyes:

Dave

#13 DaveO

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Posted 30 December 2016 - 00:11

Here's a very interesting paper (from the point-of-view of a Chemical Nerd who always asks HOW rather that WHY)

J Exp Biol 63 (16) 5741-5749 2012
Lessons from flower colour evolution on targets of selection
CA Wessinger and MD Rauscher
http://jxb.oxfordjou...1.full.pdf+html

on page 5743 there is a chart of the anthocyanin pathway which explains how the colours of flowers change from red to blue in evolutionary terms.

It also shows which flavonols are associated with each pathway and lo and behold, my old friend Kaempferol has a walk-on part in the route to red pelargonidin flowers.

This is the pigment responsible for the yellow colour of our Aussie wattles (Acacia sp) and which just happens to have a strong UV absorption at around 365 nm. The pathways to cyanidin (blue/green) and delphininidin (blue) also have strong UV absorbing flavonols with quercitin and myrcetin respectively. So each pathway has a flavonol which could produce UV absorbing patterns on the flowers due to these compounds which are not coloured in visible light.

What this means, I think, is that all the genetic machinery to produce UV patterns is there in all the genomes of the flowers and they can be expressed by regulation of various enzymes in the plant.

Dave

Edited by DaveO, 30 December 2016 - 00:25.


#14 Andy Perrin

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Posted 30 December 2016 - 02:32

Makes me wonder about hydrangeas, which can change color from pink to blue based on pH, even for different flowers on the same plant.

#15 Andrea B.

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Posted 30 December 2016 - 07:26

Add aluminum sulfate to acidify the soil. The anthocyanin pigment in the hydrangea flower picks up Al and becomes very blue. Add lime to the dirt instead, block Al pickup and then pigment turns pink. Differences in distribution and amounts of the soil amendments and differences in internal transportation can cause pink and blue on the same plant.
[This is from one of my gardening books. "-) ]


Dave, it would seem that in order to be a modern botanist one must know an awful lot of organic chemistry in addition to being well versed in evolution theory. That is quite a paper! Wasn't that fascinating about the color shifts due to a change in pollinator? I got the basics of the argument about regulatory versus other mutations but didn't quite grasp all the details. It's been a bit too long since I studied some of these things.


Andrea G. Blum
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#16 DaveO

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Posted 30 December 2016 - 23:00

Andrea, my organic chemistry goes back to the days of Fieser & Fieser "All Altruists Gladly Make Gum In Gallon Tanks" that's a secret password to the world of 1960s organic chemistry! The thing that really bothers me is how hard it is to get even references, let alone free PDFs, of stuff that I know must be there from the "heroic days" of pre-1940 natural products chemistry right here in Australian university labs (like the yellow wattle pigment which was part CXXVII of a series of papers from Uni Sydney in 1924!) I think I might write a paper for our Aussie chemistry mag and see what comes out of the woodwork. There's heaps of stuff about molecules from leaves but very little I can find about the pigments in the flowers. I know it was hard in those days especially because you had to separate the witches brew in the flowers which is probably there in trace amounts. My bible from those days Chemical Abstracts is behind a strong pay wall!

I really must get serious about keeping track of all the stuff I download and print out. Do you have a good piece of software to organise your references, my filing cabinets were always chaotic.

Happy New Year

Dave

#17 JCDowdy

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Posted 03 January 2017 - 13:22

A good piece of software to organize your references is EndNote.

#18 DaveO

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Posted 03 January 2017 - 22:57

Thanks John,

It looks like the way to go.

Cheers,

Dave

#19 JCDowdy

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Posted 03 January 2017 - 23:22

You are most welcome.

#20 DaveO

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Posted 07 February 2017 - 00:39

Yet another reference:
The anatomy of flower colour
https://phys.org/new...05-anatomy.html
How to colour a flower: on the optical principles of flower coloration
http://rspb.royalsoc...3/1830/20160429

I'm still trying to track down a copy, I tried to buy a view but the website just spat it out even before asking for my credit card. I've had a response back from the publisher so hopefully I will end up with a PDF by some means. The first ref about it seems good.

Dave