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Since carotene has been proven to affect orange and yellow how about red? There is a lot of underling yellow that comes to the surface in my test subjects so how about Indigo Red? Can a high carotene diet provide the necessary ingredients to lock in the red if given from birth? Will it intensify the red? My hunch is YES.
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"Life without risk is to merely exist."

"Since carotene has been proven to affect orange and yellow how about red? There is a lot of underling yellow that comes to the surface in my test subjects so how about Indigo Red? Can a high carotene diet provide the necessary ingredients to lock in the red if given from birth? Will it intensify the red? My hunch is YES."

hi bill,

it would be interesting to test your idea. many moons ago i studied coloration in Sceloporus lizards and was certain that carotenoids were involved. i garnered the help of some people from your neck of the woods (KU) and we found that the majority of the color (yellow and orange) were due to pterydines (same as in the turtles that had been investigated at the time. another interesting finding is that the iridophores (specifically the reflecting platelets) can not only reflect the classic whites, blues, silver, gold, etc., but also yellows, oranges, and reds. check out papers by randy morrison and sally frost.

my understanding is that most of these colors are due to pterydines, but there's certainly room for xanthophore (carotenoid) interaction.

matt

Do you know by what mechanism the pterydines will loose or gain color? Since in captivity there is a fading of color in quite a few snakes? Does the sunshine play a pivitol role?
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"Life without risk is to merely exist."

In humans excessive carotene will turn the skin orange. In birds of prey high carotene will turn the feet and cere schoolbus yellow and orange except in Gyr Falcons. In Bearded Dragons it will turn them orange. What is the mechanism used in the study at KU?

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"Life without risk is to merely exist."

the basic difference between carotenoids and pterydines is, as you know, carotenoids are derived from diet (especially in birds and fish), whereas pterydines are manufactured metabolically -- so diet plays no direct role. as you mentioned with bearded dragons and as we've discussed for varanids, there are some carotenoids (e.g. lutein) dervied from the diet that are deposited in the skin.

when we looked at the sceloporus i worked with, the KU folks used transmission electron microscopy to look at the organelles (reflecting platelets) in the iridophores that housed the guanines and other nitrogenous compounds that reflect the specific wavelengths. we used chromotography (paper and thinlayer) to identify the pterydines.

as far as the pigment deposition mechanism -- that's the $54K question. in the lizards i worked with the coloration was sexually dimorphic and i showed that sex steroids were responsible for development of color.

in captivity the coloration faded, but it was soon restored when marked lizards were returned to the wild. i suspected UV stimulation, but never tested it. these sceloporus are found over a mile high (near boulder, co) and subject to intense insolation. when brought into the lab, all color faded, the melanin as well as the yellows and oranges.

matt

Did you test any actual muscle tissue for carotenoids. I am wondering if the flesh like in salmon darkens thus showing through the translucent portion of the skin. I have noticed in my unicolor Cribos the scales do not change color but the ventral scales turn yellow as does the skin between the scales. In the Trans Pecos Ratsnakes they get no sun but some will blush orange when fed carotene. Did you compair carotene against the carotenoides synthetic or natural?
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"Life without risk is to merely exist."

bill, i don't experiment but i know that uni's do get a buttery yellow w/ age & size esp. the skin between the scales w/ or w/out additives. this is an 03 holdback female, almost 7' now that's about to melt. she eats rats exclusively & was selectively bred to look this way.....

"Did you test any actual muscle tissue for carotenoids."

no, we didn't test per se, but i looked at plenty of muscle during surgeries (gonadectomies) and didn't see any reddish tints. their muscles are basically clear (anaerobic white fibers), so it would be fairly noticeable.

"I am wondering if the flesh like in salmon darkens thus showing through the translucent portion of the skin. I have noticed in my unicolor Cribos the scales do not change color but the ventral scales turn yellow as does the skin between the scales. In the Trans Pecos Ratsnakes they get no sun but some will blush orange when fed carotene."

in the one varanid we had been feeding newly hatched (yolk-rich) chicks, the skin was very yellow. not the scales, but as you noticed, the skin between the scales. during surgery, the skin contained the yellow pigment, very obvious from the underside, and again, the muscle was clearish -- no yellow.

"Did you compair carotene against the carotenoides synthetic or natural?"

we tried organic skin extractions for carotenoids. if i recall correctly, hexane, chloroform, and a couple of others that were outlined in a reference manual on animal pigmentations. we ran one skin sample on HPLC to look for obvious peeks, but nothing jumped out. the fact that pterydines we identified were specific for the particular color of the beast (yellow vs. orange), suggested to us that we were looking at metabolic pigments and not dietary pigments.

another generality (and i'm sure there are exceptions as with everything in biology) is that dietary pigments tend to be diffusely deposited in tissues of the same type (salmon muscle, human skin after lots of carrots, the yellows you're seeing in snake skin, the yellow in our monitor). whereas colors that are laid down in specific regions/patterns may be more specific to pigments laid down by specific pigment-cell (chromatophore) distributions. of course, a diffuse increase in a dietary pigment can intensify a pigment specifically held within a chromatophore.

cool stuff,

matt

I feed this one Lysurgic Acid Dithalitamide.

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"Life without risk is to merely exist."

Lucy in the Sky with Diamonds!