Javascript Disabled Detected

You currently have javascript disabled. Several functions may not work. Please re-enable javascript to access full functionality.

How do native fish achieve blue coloration?

Started by Guest_EricaWieser_* , Oct 26 2011 08:38 AM

Reply to this topic

15 replies to this topic

#1 Guest_EricaWieser_*

Guests

Posted 26 October 2011 - 08:38 AM

What technique do native fish use to achieve a blue coloration? I've heard of a couple different explanations, but I'm not sure which species does which technique. From the Tyndall Effect or Rayleigh Scattering (http://en.wikipedia..../Tyndall_effect ) to collagen arrays (http://jeb.biologist...4/2409.full.pdf ), to the blue chromatophores found in mandarinfish (http://www.bioone.or...2108/zsj.12.811 ), there are a lot of different ways to get blue coloration. I think I heard once that butterfly wings are blue because they've got nanoscale physical ridges in the wings that reflect blue (http://www.nisenet.o...fly_wing_ridges ).

I've heard that what makes the stripes of Elassoma gilberti males blue is the guanine explanation, that stacks of purines scatter light with the Tyndall Effect.
Here's a picture of an Elassoma gilberti: http://gallery.nanfa...resize.jpg.html
Is this the same technique that darters use? How about orange spotted sunfish? Rainbow shiners?

Edited by EricaWieser, 26 October 2011 - 08:43 AM.

#2 Michael Wolfe

Board of Directors

North Georgia, Oconee River Drainage

Posted 26 October 2011 - 12:44 PM

Brady Porter has done some work on this, you should look him up and see if you can get some of his papers... he presented some of this at teh 2003 convention in Alabama.

Either write something worth reading or do something worth writing. - Benjamin Franklin

#3 Guest_blakemarkwell_*

Guests

Posted 26 October 2011 - 01:47 PM

Hey Erica,

I certainly can't answer that question for all native fishes, however, Etheostoma do contain some pigments that need to be praised. Obviously, the color that cells portray are due to molecules, which fall into two distinct classes: biochromes and schemochromes. Biochromes are true pigments, meaning they selectively absorb parts of the visible light spectrum. These differ from schemochromes in that they do not rely on structural refraction or scattering to portray hues. Thus, schemochromes produce coloration through reflecting certain wavelengths of light and transmitting others, by causing light waves to interfere within the structure or by scattering the light which falls upon them. With regard to biochromes: erythrophores, melanophores, and xanthophores are commonplace among vertebrates, however, cyanophores are incredibly rare. Most of the blue and green hues you see in other vertebrates (such as Ambystoma laterale, Hyla cinerea, etc) are coming from schemochromes contained in iridophores that rely on structural refraction or scattering, not true pigments, or biochromes.

For percid enthusiasts, this is where the story gets interesting. Remembering that cyanophores are incredibly rare among vertebrates, they have been found in all Etheostoma thus far examined (to my knowledge) that display blue or green hues to the naked eye! Flashing images of the unbelievable blues and greens of nuptial Etheostoma blennioides, E. caeruleum, E. luteovinctum, and E. zonale should be coming to mind. Indeed, studies have shown that these colors come from biochromes found within cyanophores, which are an incredibly recent chromatophore subclass added to the list. While the aberrancy of this cannot be overstated, it has also been found in marine perciform fishes in the family Callionymidae (Mandarinfish), in addition to anurans belonging to the families Centrolenidae (Glass Frogs) and Dendrobatidae (Poison Dart Frogs). Even though we did not need another one, here is one more reason to drool, marvel, and protect this magnificent radiation of perciform fishes endemic to North America!

Edited by blakemarkwell, 26 October 2011 - 01:52 PM.

#4 Guest_FirstChAoS_*

Guests

Posted 27 October 2011 - 12:04 AM

Wow, never realized the occasional blue cheeks in tesselated darters are so special? (Does anyone know if the blue cheeks are a breeding male trait or not? Not all the tessies have it).

#5 Guest_farmertodd_*

Guests

Posted 27 October 2011 - 10:07 AM

I would venture that is light scattering and possibly even before it hits the fish, up in the atmosphere. Blue wavelengths are the most powerful in the visible spectrum, which is why deep water pictures are so blue, for example. With cloud cover, the other wavelengths get filtered, and you tend to notice the blue hue. It would normally be masked by the remainder of the light spectrum, which would appear more white.

If you look back, almost every fall someone posts a picture of a purple bluegill in the north

I suspect that's what you're seeing on the tesselated.

Todd

#6 Guest_blakemarkwell_*

Guests

Posted 27 October 2011 - 10:19 AM

I bet it is too. That brings up something I forgot to add -- not all the darter blues and greens you see come from biochromes per se, but all the bold blues and greens analyzed that look like they're coming from pigments, have been.

If my above post appears a bit scripted, it's because it is -- it was part of an American Currents article that I started and never got around to finishing. Erika, I also realize that you didn't need the introductory information, as your original post shows that you understand the difference between pigments and scattering/reflectance, but it's nice to have the information on the forum for those that don't. :biggrin:

#7 Michael Wolfe

Board of Directors

North Georgia, Oconee River Drainage

Posted 27 October 2011 - 11:13 AM

I bet it is too. That brings up something I forgot to add -- not all the darter blues and greens you see come from biochromes per se, but all the bold blues and greens analyzed that look like they're coming from pigments, have been.

If my above post appears a bit scripted, it's because it is -- it was part of an American Currents article that I started and never got around to finishing. Erika, I also realize that you didn't need the introductory information, as your original post shows that you understand the difference between pigments and scattering/reflectance, but it's nice to have the information on the forum for those that don't.

Finish that article... I thought your post was great and almost told you so... now that I know it is part of an almost article... Finish that article... AC needs good content like that!

Either write something worth reading or do something worth writing. - Benjamin Franklin

#8 Guest_EricaWieser_*

Guests

Posted 27 October 2011 - 11:41 AM

I would venture that is light scattering and possibly even before it hits the fish, up in the atmosphere. Blue wavelengths are the most powerful in the visible spectrum, which is why deep water pictures are so blue, for example. With cloud cover, the other wavelengths get filtered, and you tend to notice the blue hue. It would normally be masked by the remainder of the light spectrum, which would appear more white.

Here is a netted and photoboxed male elassoma gilberti, to show that atmospheric light still scatters blue on their sides.
Netted: http://gallery.nanfa...resize.jpg.html
Photo boxed: http://gallery.nanfa...ze_001.jpg.html

#9 Michael Wolfe

Board of Directors

North Georgia, Oconee River Drainage

Posted 27 October 2011 - 11:46 AM

Here is a netted and photoboxed male elassoma gilberti, to show that atmospheric light still scatters blue on their sides.
Netted: http://gallery.nanfa...resize.jpg.html
Photo boxed: http://gallery.nanfa...ze_001.jpg.html

I don't know what you are trying to show... but any difference between a fish in a net and a fish in a tank could be hundreds of things that changed... including the fact that the fish themselves actively change color over the a couple of seconds of time difference.

I have seen the same fish change color in a tank based on tank mates, background color, food, so you cannot just base any of this on difference in light sources.

Either write something worth reading or do something worth writing. - Benjamin Franklin

#10 Guest_EricaWieser_*

Guests

Posted 27 October 2011 - 11:49 AM

I don't know what you are trying to show...

That they aren't blue just because they're deep underwater and that's the only color available to reflect. The post I quoted said "With cloud cover, the other wavelengths get filtered, and you tend to notice the blue hue." and I was just pointing out that the fish are blue above water, too.

Edited by EricaWieser, 27 October 2011 - 11:50 AM.

#11 Guest_farmertodd_*

Guests

Posted 27 October 2011 - 11:58 AM

and I was just pointing out that the fish are blue above water, too.

Which can be derived from available light, atmospheric filtering or pigments or in the case of your pygmy sunfish, probably ALL THE ABOVE.

And I agree with Michael, Blake. Do you have any of the work Rex Strange did with color receptors in darters? I can look up some citations, I think Karen got at least one of the papers published. Might be an extra angle to work in. Wasn't that a NANFA grant too?

Todd

#12 Guest_fundulus_*

Guests

Posted 27 October 2011 - 12:24 PM

Which can be derived from available light, atmospheric filtering or pigments or in the case of your pygmy sunfish, probably ALL THE ABOVE.

And I agree with Michael, Blake. Do you have any of the work Rex Strange did with color receptors in darters? I can look up some citations, I think Karen got at least one of the papers published. Might be an extra angle to work in. Wasn't that a NANFA grant too?

Todd

Yes, it was a NANFA Conservation Research grant project that Rex (if I remember correctly) presented at a NANFA convention rather than have it published in AC.

#13 Guest_haruspicator_*

Guests

Posted 28 October 2011 - 01:15 PM

So in general are the metallic colors, such as in sunfish and pupfish, schemochromes that cause interference? Or a combination of both?

I been thinking lately how some fish can 'fade' when stressed (or feel like fading or whatever), such as in a net, and been meaning to do a lit search on how they do it......someday....

Thanks for the discussion, shawn

#14 Michael Wolfe

Board of Directors

North Georgia, Oconee River Drainage

Posted 28 October 2011 - 02:10 PM

So in general are the metallic colors, such as in sunfish and pupfish, schemochromes that cause interference? Or a combination of both?

Good question... what makes this so metallic looking?
Posted Image

Either write something worth reading or do something worth writing. - Benjamin Franklin

#15 Guest_blakemarkwell_*

Guests

Posted 28 October 2011 - 07:52 PM

Metallic colors in fish usually come from white (leuco-) or silvery (irido-) chromatophores that contain organic crystals that reflect light to display various metallic colors. With the Doration you've shown, since it's a darter, the blue color is most likely coming from a cyanophore with some chromoprotein that produces a blue hue. The metallic color could be coming from overlapping iridophores or leucophores with organic crystals that produce the metallic hue via reflection/scattering or it could be some novel combination that waits to be studied. There's tons of chemical groups out there and endless interactions they can form. Sometimes carotenoids will join up with a chromoproteins to create a carotenoprotein that will produce a different color than the chromoprotein alone via spectral shifts. The aforementioned example is somewhat common in invertebrates, and is the reason that boiling a blue lobster (such as Homarus gammarus) will cause it to turn red, as the carotenoid is liberated when the cooking process denatures the natural blue pigment of the carapace. No, I'm not suggesting that you boil any nuptial Doration! :mellow:

Unfortunately, a lot of this stuff hasn't been studied (especially on the species or genus level), but metallic colors in vertebrates seem to always (never use this word in science) come from the process I mentioned.

Edited by blakemarkwell, 28 October 2011 - 08:32 PM.

#16 Guest_haruspicator_*

Guests

Posted 29 October 2011 - 10:20 PM

I thought I've read something somewhere a while back stating that industry and scientists are looking at these pigments in birds to develop new types of paint or other coatings. Seems that this may be another reason of many to conserve native fish.