Greeting Guys from Newbie and a cardinal tetra questions. :)

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nanyangview

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Jan 31, 2003
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Halooo guys...this is my first post in this forum and nice to meet all of u the FISH Veterans haha.
I currently own a heavily planted 10USG Cardinal Tank with 12 lovely Cardinal Tetras and 2 amano shrimps. Some of my plants include: baby amazon sword, Tiger lotus, limnophila aquatica, java moss and anubias....and more.

Cardinal Tetra is my fav fish and IMO i think they are the prettiest freshwater fish available hehe. So here is my question, what is the thing that makes their body glow? That iridescent blue strip? Is it a type of reflective material or chemical that reflect with the presence of light? I tried to look around on the net but could not find any answer. So maybe some of u guys know the answer hehe..

THanks!
 
Hmm, not a newbie question after all!

Black pigment cells, called "melanophores" because they bear the black pigment melanin, occur in almost all freshwater fishes except albinos and a few depigmented ("amelanic") cave fishes. When melanophores are placed near iridocytes or leucophores, which bear the silvery or white guanins, they produce structural colors of blue and green. These structural colors are often intense, because they are formed by the refraction of light through the needle-like crystals of guanin when red and yellow wavelengths are absorbed by melanin. Think of the structural colors of changeable blue-green on some tropical butterfly wings; those colors are produced by diffraction-grating effects on the surprisingly intricate surface of wing scales, structures that are visible only with the electron microscope. On a fish, light is reflected back through successive ultra thinly-layered films contained within the dermis. Whether the colors appear variously iridescent or not depends upon the relative thickness of the layer and the interlaminar spaces. The giveaway is in the slight changeableness that depends on your viewing angle. A good example of a structural color is the black green of "Mossy Green" Tiger Barbs. This effect is called the "Tyndall effect" for John Tyndall (1820-1893), the British physicist who first explained the phenomenon.

--from www.skepticalaquarist.com in the "Fishes" folder, hidden among Miscellaneous.
 
Hmm... I respect Wetmans expertise but this may NOT be the mechanism which makes Cardinals glow.

My Cardinals are a different fish at night.
When I switch on the light for a brief time at night
(I know I am a *******) and wake the fish they have
none of the colors.
That are mainly dirty/transparnt with a pale red spot
and their color fluro belt is not there.

In your description it sounds like its refracted light
from the dermis. If that were so, it would not
explain the color change when you 'wake' them.
Unless they change the structure of the skin when
they slee. Unlikely.

My WAG is that they have pigmentation sacks
like Kalamari do.
 
Yeah, how come the color can come and go? Diffracting, reflecting, and all that other stuff light does sounds good, but like Wulfy said, you turn on the LIGHT and the color isn't there???????

BTW - With all due respect, I 2nd OrionGirl's statement!
 
I have also often wondered about why the fish "go colorless" at night, but just as observed before the first min or so after i turn on the lights in the morning they are all but colorless.
 
Its probably something like those glow in the dark things you can get in dollar stores, well not all of them but the ones you have to let sit in the light for liek 20mins before they will glow in the dark. Hope you all know what i mean =/. Anyway im thinking it could be like that and at night with no light then the cells go dormant and take a couple of minutes to start reacting again when the light is turned on suddenly. Very few biological reactions are instantaenous in my rather limited knowledge
 
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