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Hatches Blog Post - How UV and fluorescent materials work


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#1 SmallieHunter

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Posted 08 December 2014 - 11:19 AM

A great breakdown of light properties and how light impacts color and treatment of fly tying materials.

View the full article

#2 heavynets

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Posted 08 December 2014 - 02:22 PM

Are there any insects, minnows, crawdads, etc. in nature that have a fluorescence effect when exposed to UV light?

#3 SilverCreek

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Posted 08 December 2014 - 08:54 PM

There are two issues. One is whether adult  salmonids can see UV reflected colors as the video states. Very young trout have 4 color cones, instead of the 3 cones humans have. One of the cones is centered at 355 nm which is in the UV range.

 

This is the one that is said to "recede" in the scientific article. I think the article below is the one that the video refers to:

 

http://www.ncbi.nlm..../pubmed/3447359

 

"Abstract

 

Microspectrophotometric analysis of the visual receptors of "yearling" brown trout, Salmo trutta, revealed three cone types, double cones with visual pigments absorbing maximally at about 600 and 535 nm, and two types of single cone with lambda max at about 440 and 355 nm. Two-year-old fish did not possess the u.v. cone cells. Microscopical analysis of the cone mosaic in "yearling" trout showed a square pattern of double cones with a central single cone and corner single cones, but in two-year-old trout the corner cones were absent. It is concluded that u.v. sensitivity is derived from the corner cones of the mosaic, and that it is only present in young trout."

 

The other issue is how humans can match a UV Color when we don't see into the UV range.

 

 

Overmywaders (Reed Curry) would and has argued that the salmonids are able to "see" UV light even in the absence of UV specific receptors because the receptors have a wide band of stimulation. So although the "sweet spot" of the cone sensitivity is not UV, the UV does still stimulate some of the cones. My concern with this argument is that a non UV cone reaction to UV light is that any stimulation of that cone would be interpreted by the fish as not UV, but the color that the cone is centered on. If the 440 nM cone above reacted to UV light it would be interpreted by the brain as the color Purple and not UV. All trout brain would know is that the Purple color cone at 440 nM was being stimulated. So the area of UV would look as if it was a bit Purple color.

 

spectrum.jpg

 

 

Furthermore, I think Reed would also disagree that the UV specific receptors at 355 nm in the young trout are not active in the older trout. Reed believes that some of them still are according to some recent research in a certain area of the retina. From my reading, the research is controversial and my impression most trout biologists still believe that the UV specific cones are not active in adult with the exception of spawning salmon. So the research is in flux.

 

 

 


Regards,

Silver

"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

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#4 shoebop

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Posted 09 December 2014 - 12:11 PM



If you haven't seen enough on UV, here is a video I came across that explains things pretty well.
Shoebop

#5 overmywaders

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Posted 24 December 2014 - 04:44 PM

I'm not sure Silver is representing my view of UV sensitivity properly. Rather than write it all yet again, I refer any interested to http://www.overmywaders.com/cblog/index.php?/archives/112-Ultraviolet-Vision-in-Trout.html 

 

You will note that not only do the cones of mature trout respond to UV, but the rods, which are used at dusk and nighttime, do as well. As for what "color" the ultraviolet wavelengths represent to trout, we cannot know for certain. We do know from our experience with aphakic humans (those people lacking the protective yellow pigment in the lens or lacking the lens itself) that humans "see" (interpret or perceive) ultraviolet as shades of pale blue. The opsins of trout and man are similar in their transmissions - trout have peaks at 434, 531, and 576nm, while humans have peaks at 420, 530, and 560nm.
 

However, it is not relevant what color UV appears to trout -- if the natural insect is seen with UV markings, the artificial should have similar markings. We treat all the colors we can see the same way: if an insect has sulphur yellow wings, we don't ask what color the trout sees, we replicate the sulphur color in our flies. The same should apply to UV.

 

Regards,

Reed



#6 SilverCreek

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Posted 04 January 2015 - 04:54 PM

I'm not sure Silver is representing my view of UV sensitivity properly. Rather than write it all yet again, I refer any interested to http://www.overmywaders.com/cblog/index.php?/archives/112-Ultraviolet-Vision-in-Trout.html 

 

You will note that not only do the cones of mature trout respond to UV, but the rods, which are used at dusk and nighttime, do as well. As for what "color" the ultraviolet wavelengths represent to trout, we cannot know for certain. We do know from our experience with aphakic humans (those people lacking the protective yellow pigment in the lens or lacking the lens itself) that humans "see" (interpret or perceive) ultraviolet as shades of pale blue. The opsins of trout and man are similar in their transmissions - trout have peaks at 434, 531, and 576nm, while humans have peaks at 420, 530, and 560nm.
 

However, it is not relevant what color UV appears to trout -- if the natural insect is seen with UV markings, the artificial should have similar markings. We treat all the colors we can see the same way: if an insect has sulphur yellow wings, we don't ask what color the trout sees, we replicate the sulphur color in our flies. The same should apply to UV.

 

Regards,

Reed

 

I totally agree that we should replicate the colors including UV. My question is how is that done when we as humans cannot "see" UV. How can we be sure that the pattern we have tied actually matches the natural?

 

Nature varies the color of identical species from location to location. For example, there is a wide variation in PMD (Ephemerella excrucians) coloration. So even within a single species of mayfly, we can see the variations in both the color and shade of colors. When we can see the color, we can match it to the dubbing. I am assuming that this  variation also occurs with UV so that the wavelength and color saturation of UV within a species is not fixed. If that is true, is there a practical way to match UV color? Are there UV dubbings that are specifically made to match the visible and UV spectrum of naturals? If so what brands do you recommend for matching the naturals. That would be very helpful.

 

I do not doubt that UV colors exist in the food that fish eat. My question is what specific method is used to match those colors?


Regards,

Silver

"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

http://tinyurl.com/lgkbu7v

#7 J-Kno

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Posted 05 January 2015 - 12:42 AM

Could you flood bugs with the UV spectrum (400nm-10nm) to see what and where they "light up"? Coming up with a multi-LED light source with different wavelengths represented wouldn't be too difficult to do...



#8 SilverCreek

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Posted 06 January 2015 - 08:19 PM

And how would the fly tyer match the UV spectrum of the "bug" parts with tying materials which reflect a UV color spectrum the tyer cannot see?

 

The problem is two fold.

 

1. The reflective color spectrum of insects "drift" or change from location to location. One of the most important mayflies is the Pale Morning Dun and this species varies in color depending on the river system.

 

2. Humans cannot see the reflective UV color spectrum of tying materials.

 

The result is that it would theoretically be possible to match a given "bug" for a given location and time by mixing and photographing in UV until the dubbing mixture matched, but we cannot do that for all locations as we can with colors that we can see and match with our own eyes.

 

It is not enough to know that trout food reflects UV. To actually make practical use of that knowledge, there must be a system that can match the UV color spectrum as we do with colors we can see.

 

I do not doubt that trout foods reflect UV. There is disagreement among experts as to whether adult non spawning trout can see UV. Lets put that disagreement aside and assume that trout see UV just fine. How do we apply that knowledge in a practical fashion?

 

I think the current "UV" materials are for the most part UV fluorescent materials that have nothing to do with matching the UV reflectance of natural trout food.


Regards,

Silver

"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

http://tinyurl.com/lgkbu7v

#9 overmywaders

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Posted 12 January 2015 - 12:11 PM

Silver,

 

Why do you constantly reference the irrelevant UV-specific cone controversy? As in 

 

 

There is disagreement among experts as to whether adult non spawning trout can see UV. Lets put that disagreement aside and assume that trout see UV just fine.

That is a strawman and quite beneath your intelligence and dignity. There is no "disagreement among experts as to whether adult non spawning trout can see UV" through the use of their SW, MW, and LW cones and their rods. 

 

Okay, to the quandary which you encapsulated in the statement: "It is not enough to know that trout food reflects UV. To actually make practical use of that knowledge, there must be a system that can match the UV color spectrum as we do with colors we can see."

 

I concur. I have already photographed a large selection of natural fly-tying materials and presented them in my book - http://www.amazon.co.../dp/0984086307/  Did you have a chance to look through it for hints on materials and their UV reflectivity?

 

I really need to do a rewrite and include tables of references by UV reflectivity and material type. Unfortunately, the UVR of one supplier's products may differ from that of another supplier.

 

Let us say that you wish to imitate the body of an artificial PMD with the UVR of the natural dun, which is, for the sake of this example, a pale olive. You know that the Hareline natural rabbit dubbin' looks like the image on the left in visible light and the right in UVR.

 

RabbitDubbin300px.jpgRabbitDubbinUV1WB300px.jpg

 

As the light-bodied Ephemera have, based upon my observations, a fairly high UVR (60%+), you could mix the light olive in the second row left, with the white in the second row, third from left.That would give you the light olive dubbing withe the appropriate UVR.

 

I wholeheartedly agree with your statement - "I think the current "UV" materials are for the most part UV fluorescent materials that have nothing to do with matching the UV reflectance of natural trout food."

 

Kind regards,

Reed



#10 SilverCreek

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Posted 14 January 2015 - 12:24 AM

 

 

Okay, to the quandary which you encapsulated in the statement: "It is not enough to know that trout food reflects UV. To actually make practical use of that knowledge, there must be a system that can match the UV color spectrum as we do with colors we can see."

 

I concur. I have already photographed a large selection of natural fly-tying materials and presented them in my book - http://www.amazon.co.../dp/0984086307/  Did you have a chance to look through it for hints on materials and their UV reflectivity?

 

I really need to do a rewrite and include tables of references by UV reflectivity and material type. Unfortunately, the UVR of one supplier's products may differ from that of another supplier.

 

Let us say that you wish to imitate the body of an artificial PMD with the UVR of the natural dun, which is, for the sake of this example, a pale olive. You know that the Hareline natural rabbit dubbin' looks like the image on the left in visible light and the right in UVR.

 

RabbitDubbin300px.jpgRabbitDubbinUV1WB300px.jpg

 

As the light-bodied Ephemera have, based upon my observations, a fairly high UVR (60%+), you could mix the light olive in the second row left, with the white in the second row, third from left.That would give you the light olive dubbing withe the appropriate UVR.

 

I wholeheartedly agree with your statement - "I think the current "UV" materials are for the most part UV fluorescent materials that have nothing to do with matching the UV reflectance of natural trout food."

 

Kind regards,

Reed

 

 

 

Reed,

 

Thank you so much for responding. I want to make sure I understand you correctly.

 

It seem to me from your example, that for fly tyers to mix dubbing so the dubbing's color reflection matches the actual insect color we can see and the UV refection we cannot see:

 

1. The wavelength of UV that trout can see reflected from the insect must match the wavelength of UV reflected from the dubbing, and

 

2. The proportion of incident UV reflected in that UV wavelength from the dubbing must also match, and

 

3. The mixture must be able to be made with the fly tier matching the visible color alone using the UV reflecting material as an additive to get the correct shading.

 

Question 1 - How do we know that the specific band (wavelength) of UVR reflected by the mayfly will be the same wavelength of UVR in the white dubbing? (does the white reflect only the UV wavelength that the natural insect reflects and no other)

 

Since you are adding the white UV reflective material to the olive in proportion to create the correct shade of light olive we can see, my question 2 is do all mayflies reflect proportionate UV to their shading and color that we can see?

 

In other words, will always adding that white dubbing be adding the correct UV wavelength reflective material for all mayflies, and would always mixing to produce the correct shade (saturation) of color we can see result in the correct "shade" of UV reflectance that we cannot see?

 

The implication from your example is that we can mix the UV reflective white to any base non UV reflective color and end up the correct UV and visible color match. Or is this only one example of a specific UV matching strategy and other strategies are used if the insect color was, for example, grey instead of light olive. Or an olive caddis instead of a mayfly? 

 

Regards,

 

Henry


Regards,

Silver

"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

http://tinyurl.com/lgkbu7v

#11 overmywaders

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Posted 14 January 2015 - 09:58 AM

Henry,

 

I'll take those questions in order.

 

 

Question 1 - How do we know that the specific band (wavelength) of UVR reflected by the mayfly will be the same wavelength of UVR in the white dubbing? (does the white reflect only the UV wavelength that the natural insect reflects and no other)

In photographing mayflies in the UV, I have found that the body reflectivity was generally 365nm to 400nm. Humans have similar cone pigments to trout and those humans who can see in the UV interpret the entire range as a bluish white, mainly varied by intensity. When we consider that blue is the range 455nm to 492nm and violet is the range 390nm to 455nm, it doesn't seem unusual for UV to have a 40nm span as gradations of one color. The intensity of the color UV may be most significant, that is, the percentage of reflected UV.

 

 

 

my question 2 is do all mayflies reflect proportionate UV to their shading and color that we can see?

Alas, I can only speak for the small set of mayflies that I photographed in the UV. From a scientific viewpoint, I lack the data to reply. However, if we extrapolate from the few known to the many unknown (a practice that is inherently wrong, though the conclusion may be correct) I would say that 40% UV reflectivity for the body of duns - with bars of lower reflectance - and 60%+ for spinners would be a safe bet.

 

 

 

The implication from your example is that we can mix the UV reflective white to any base non UV reflective color and end up the correct UV and visible color match. Or is this only one example of a specific UV matching strategy and other strategies are used if the insect color was, for example, grey instead of light olive. Or an olive caddis instead of a mayfly?

As noted in my reply above, I am extrapolating from a small sample. However, I can say authoritatively that visible color bears no relation to UV "color". See the Brown-eye Susan below in visible light and UV:

BESusanVis800.jpg

BESusanUV800.jpg

 

BTW, I noticed a new - 2013 - study on yearling brown trout using UV in predation of sticklebacks. See http://www.currentzo...7BF3A0F365}.pdf

 

Kind regards,

Reed



#12 SilverCreek

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Posted 14 January 2015 - 01:46 PM



Henry,

 

As noted in my reply above, I am extrapolating from a small sample. However, I can say authoritatively that visible color bears no relation to UV "color". See the Brown-eye Susan below in visible light and UV:

BESusanVis800.jpg

BESusanUV800.jpg

 

BTW, I noticed a new - 2013 - study on yearling brown trout using UV in predation of sticklebacks. See http://www.currentzo...7BF3A0F365}.pdf

 

Kind regards,

Reed

 

 

 

Reed,

 

By deductive reasoning, I think we can safely say that if the UV spectrum reflectivity can be matched in the imitation, it really does not matter that visible color bears no relation to UV "color".

 

By taking photos in UV, the camera "translates" the invisible reflected UV spectrum into the visible spectrum that we can see. So we are seeing a representation of the reflected UV in location and relative intensity. If we match UV spectrum (actual wavelength) to the location and relative intensity; the reflected UV will match the natural and the trout will "see" the UV color as matching.

 

Just like individual naturals in the same hatch have some variation in visible color, I also suspect that the naturals will have some variation in UV "color" as well.


Regards,

Silver

"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

http://tinyurl.com/lgkbu7v

#13 overmywaders

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Posted 14 January 2015 - 05:39 PM

I agree. I said that in response to the statement "other strategies are used if the insect color was, for example, grey instead of light olive." I should have been more explicit, the same strategy is valid for all visible colors if the natural is of a type with that UVR. So, I would add some white Hareline rabbit dubbing for all mayfly dun bodies, and more for mayfly spinner bodies.

 

Did you have a chance to look at the study? The trout were of a size to have lost most of their UV-specific cones, yet they chose the sticklebacks where UV markings were visible over those with no UV visible markings. From the abstract: 

 

The difference in attack probability corresponded

to the difference in chromatic contrasts between sticklebacks and the experimental background calculated for both the
UV+ and UV- conditions in a physiological model of trout colour vision. UV reflections seem to be costly by enhancing the risk
of predation due to an increased conspicuousness of prey. This is the first study in a vertebrate, to our knowledge, demonstrating
direct predation risk due to UV wavelengths 

Regards,

Reed



#14 SilverCreek

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Posted 14 January 2015 - 10:10 PM

The article is very convincing for the year old brown trout using UV for predation when previously fed sticklebacks (conditioned) for some time prior to the experiment. If I am to be very specific, it demonstrated that trout can be conditioned to use UV to identify food when fed UV reflecting food. It demonstrates the these yearling fish have the potential and that they exercise their UV vision to identify food.

 

Brown trout... from a commercial aquaculture company ...were held in 700 L outdoor tanks provided with continuously fresh water flow- through and air ventilation. Trout were fed daily with commercial fish pellets and additionally with defrosted chironomid larvae ad libitum. Furthermore, trout were fed with dead sticklebacks and they were starved for one day before the start of the experiment

 

The experimental protocol should be repeated also for rainbow and brook trout and then for mature trout. These fish should be captured wild fish.

 

1. Reproducibility by another team of investigators is important.

2. As is demonstrating the same result for other trout

3. And proving that this form of predation continues in adulthood.

4. The experiment used aquaculture trout which were conditioned to feed on sticklebacks. Further studies on wild fish would demonstrate to what degree this behavior also exists in wild fish without previous conditioning.


Regards,

Silver

"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

http://tinyurl.com/lgkbu7v

#15 overmywaders

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Posted 15 January 2015 - 10:28 AM

Silver,

 

You missed the following in the Discussion paragraphs:

 

In the present study, the UV-reflecting sticklebacks

were attacked first significantly more often. Subsequent
attacks of trout only tended to be more frequently targeted
at the UV reflecting one. Assuming a similar success
of hunting by trout for both the UV-reflecting and
non-reflecting stickleback once attacked, the UV-reflecting
one will suffer a higher risk of being detected and
preyed upon. The matter of fact that trout were fed with
dead sticklebacks under UV+ holding conditions prior
to the experimental trials might have accounted for the
preference for UV+ prey because it looked similar to the
food previously experienced. Nevertheless, trout were fed
with dead stickleback only on very few occasions so that
some sort of learning effect can be virtually excluded. 

 

You were very selective in your reading, or you have little regard for an honest discussion. You choose.

 

Of course, you will want studies for rainbow trout, all chars, Golden trout, cutthroat trout, Paiute trout, coelacanths, etc. :) I would expect no less from you...

 

and now, I expect no more as well.

 

Disillusioned again.