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i have this random fact book that says that if a live goldfish is kept in pitch dark for a long time, it will turn completely white.

i'm skeptical to believe anything in this book because this book happens to have two other facts that say "goldfish have a memory of 3 seconds" and "marilyn monroe had six toes" :blink:

both of which are NOT true, since the first one is obvious for anyone on this forum and the second one i did research on and it proved to be a rumor that was taken out of proportion.

just curious what you guys have to say about a goldfish turning white in the dark.

is it possible? :goldfish:

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I have 10 toes. I never thought it so odd.

;)

While it is true that many dark dwelling creatures are white- or without color, white or not, and sunlight does, indeed, affect color, I do not know if a "red" fish would actually turn white or lose color to that degree. It is something that is lost in the generations of fish - when the color no longer affects the breeding choices of the fish....

I htink I would have to guess that the fish would lose lots of color - to the point of being really pale - but would not go completely white. I also suspect that within a generation, though, the fish would lose color.

:)

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what jumped out at me was who would be so cruel as to keep a living creature in total darkness?

sure, many cave dwelling creatures are clear or white, they didnt need the pigment to protect against sunlight (or for sight as in breeding plumage, etc),nor the eyes as they see in other ways, and many have developed light producing cells in their bodies. to achieve the darkness of caves would be a undertaking in a lighted world. anyone ever been in a cave and they turn the lights off? incredible.

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I am sure sunlight definitely has to do with pigmentation and pigments that determine the color...but for a goldfish to totally turn white..it will have to be in darkness for god alone knows how long...I think for a long time...and I guess before it turns white..it will stress...long durations of darkness have been freaking my goldfish since yesterday..they come to the surface very often..oh, actually I have been treating them for a mild case if ICH so have been in the dark for long durations of time...I noticed one of my goldies got really very lethargic and just kept sleeping on the bottom...the other surfaced to the water kind of gasping for air..but it actually was not quite fond of the darkness..once it got used to the darkness it kept swimming in the tank...

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I was planning on writing a short reply, explaining some of the factors that can potentially affect the orange colouration in goldfish, but it became rather lengthier than I had first intended, and as such was more of a 'research post' than just a reply :) . I've therefore posted it on the Research Submissions subforum, but since it's awaiting approval from a moderator I'll post here it too :D .

Hope it helps :) .

(edit: because of copy-pasting, the links in the text were lost. Fixed it now ^_^)

--------

The following is meant to give a general explanation of the phenomenon of the orange colouration that is found in most goldfish and plenty of other species fish (as well as many reptiles and fish). It starts by giving a general explanation behind the origin of this colouration and proceed to discuss the various factors by which it can potentially be affected.

The orange colour in goldfish is mainly/entirely the result of the deposition of carotenoids in or right beneath the scales. Carotenoids are widely used in plants to protect the inside of the leaves from strong sunlight (towards higher frequencies, such as blue light and UV light, because these can cause the most harm). Animals also use them, either as 'anti-sun' pigmentation or as a colour display, to signal e.g. quality towards members of the opposite sex or against competitors of the same sex (many bird species are famous for this), and they also have some function in antioxidant activity (though it's still a bit unclear to what extend these are important). Importantly, most (if not all) animals cannot produce carotenoids on their own; they have to eat plant to acquire them. The deposition of the acquired carotenoids in feathers, skin or scales depends on quite a lot of factors: amount of available carotenoids (see e.g. flamingo's), the amount of light exposure, and of course genetic factors pertaining to allocation of carotenoids to the skin/feathers/scales.

In birds, I know that once carotenoids are used as pigmentation in the feathers, the birds cannot remove them actively. In goldfish I'm not sure whether or not they can remove the carotenoids after deposition (I do not know of any research that has been done with regard to this), but there does seem to be some effect of both nutrition (e.g. how rich their food is with regard to carotenoids) and sunlight exposure, though from what I have surmised from other forum members, it's rather hard to use this in any definite way to actively change the colour of your goldfish (apart that sunlight seems to 'deepen' the colours that are already present).

In theory, a carotenoid-poor diet should decrease the amount of carotenoids in the scales, since (if they're not actively removed) they still need to be replaced alongside general scale replacement/growth. Little-or-no exposure to sunlight might decrease the colour, either if the carotenoids are actively removed (and allocated to other used when not needed as pigmentation) or if light is needed to allocate new carotenoids to the skin (like humans mostly only tan when exposed to plenty of sun). This however assumes that sunlight (alongside nutrition) is the only factor influencing carotenoid allocation; it might however be possible that mate attraction plays a (large) part in this ("look at me, I'm so very orange, so you know I'm a high quality male/female") or that the tendency to allocate more vs. less carotenoids to the scales is partly or mostly genetically determined (or in combination, that the mate-attraction-based allocation is genetically determined).

In the case that carotenoid deposition is (entirely) genetically determined it might be possible to use a breeding program to come up with 'genetically white' goldfish, that stay white no matter what diet or light they are exposed to. Because of the intricacies of genetics, it may be that this can be achieved relatively quickly (in only a couple of generations, if you wisely start with goldfish that are already on the light side) or it may be (at much more likely) that you would need a very stringent breeding program to achieve a breed of goldfish that is relatively unaffected by diet of light exposure, in the sense that if you stay clear of very carotenoid-rich food and high light exposure, you usually get entirely white goldfish. I should also be noted here, that there is a different between selection for a certain trait (e.g. lack of carotenoid pigmentation) and no selection against that trait: even if carotenoid colouration is no longer required (e.g. no bright light and no role mate attraction), that trait may still remain in the population, either because it is neither positive nor negative with regard to survival or reproduction, or because the mechanism behind carotenoid allocation in intertwined with other mechanisms that are positively selected for (in which case carotenoid colouration is just 'long for the ride'). Only traits that are (practically) neutral with regard to survival and reproduction may nevertheless change over time/generations (a process called genetic drift)

To summarise, carotenoid based pigmentation is a rather complex phenomenon, that can potentially be influenced by a lot of factors, either environmental, genetic or evolutionary. Although it's as such a very interesting topic, it's therefore also relatively difficult to apply to your own goldfish, although general rules can be applies to maximize the chances of your goldfish's colouration becoming what you want it to be.

Edited by Erinaceus
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wow, erinaceus, thanks for that really informative post!

so basically the answer to my question is it really depends on a lot of factors..not solely on whether there is a lack of light or not.

i just learned something (a lot of things, to be more accurate) new! :D

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The three fish in my 55 are all white (except Rowan's wen) and they get plenty of light whether it's from sunlight through the living room window or the hood lights.

Wouldn't being in the dark mess with their sense of direction, and maybe balance? I know my balance is a little screwy when I'm lost in my dark house :P

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The three fish in my 55 are all white (except Rowan's wen) and they get plenty of light whether it's from sunlight through the living room window or the hood lights.

Wouldn't being in the dark mess with their sense of direction, and maybe balance? I know my balance is a little screwy when I'm lost in my dark house :P

Given that they'd be used to always having light, it might confuse them somewhat, but (gold)fish also have a added sensory organ, the lateral line which is basically able to feel pressure differences; image it as a kind of 'passive sonar'. I have no idea how the balance / up-is-up-perception works in (gold)fish. It might be that they use there swim bladder for this purpose as well, or maybe them employ something similar to the invertabrate system (see statocysts) or the mammalian system (see vestibular organ; though the inner ear in fish is far less complex than in e.g. mammals: see this wikipedia page for some info on the evolution of the ear after some fish turned in amphibia).

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Alain, I think you need to change your thesis from birds to fish cuz you just wrote it here! lol! :rofl It's great! What a great research submission!

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I was planning on writing a short reply, explaining some of the factors that can potentially affect the orange colouration in goldfish, but it became rather lengthier than I had first intended, and as such was more of a 'research post' than just a reply :) . I've therefore posted it on the Research Submissions subforum, but since it's awaiting approval from a moderator I'll post here it too :D .

Hope it helps :) .

(edit: because of copy-pasting, the links in the text were lost. Fixed it now ^_^)

--------

The following is meant to give a general explanation of the phenomenon of the orange colouration that is found in most goldfish and plenty of other species fish (as well as many reptiles and fish). It starts by giving a general explanation behind the origin of this colouration and proceed to discuss the various factors by which it can potentially be affected.

The orange colour in goldfish is mainly/entirely the result of the deposition of carotenoids in or right beneath the scales. Carotenoids are widely used in plants to protect the inside of the leaves from strong sunlight (towards higher frequencies, such as blue light and UV light, because these can cause the most harm). Animals also use them, either as 'anti-sun' pigmentation or as a colour display, to signal e.g. quality towards members of the opposite sex or against competitors of the same sex (many bird species are famous for this), and they also have some function in antioxidant activity (though it's still a bit unclear to what extend these are important). Importantly, most (if not all) animals cannot produce carotenoids on their own; they have to eat plant to acquire them. The deposition of the acquired carotenoids in feathers, skin or scales depends on quite a lot of factors: amount of available carotenoids (see e.g. flamingo's), the amount of light exposure, and of course genetic factors pertaining to allocation of carotenoids to the skin/feathers/scales.

In birds, I know that once carotenoids are used as pigmentation in the feathers, the birds cannot remove them actively. In goldfish I'm not sure whether or not they can remove the carotenoids after deposition (I do not know of any research that has been done with regard to this), but there does seem to be some effect of both nutrition (e.g. how rich their food is with regard to carotenoids) and sunlight exposure, though from what I have surmised from other forum members, it's rather hard to use this in any definite way to actively change the colour of your goldfish (apart that sunlight seems to 'deepen' the colours that are already present).

In theory, a carotenoid-poor diet should decrease the amount of carotenoids in the scales, since (if they're not actively removed) they still need to be replaced alongside general scale replacement/growth. Little-or-no exposure to sunlight might decrease the colour, either if the carotenoids are actively removed (and allocated to other used when not needed as pigmentation) or if light is needed to allocate new carotenoids to the skin (like humans mostly only tan when exposed to plenty of sun). This however assumes that sunlight (alongside nutrition) is the only factor influencing carotenoid allocation; it might however be possible that mate attraction plays a (large) part in this ("look at me, I'm so very orange, so you know I'm a high quality male/female") or that the tendency to allocate more vs. less carotenoids to the scales is partly or mostly genetically determined (or in combination, that the mate-attraction-based allocation is genetically determined).

In the case that carotenoid deposition is (entirely) genetically determined it might be possible to use a breeding program to come up with 'genetically white' goldfish, that stay white no matter what diet or light they are exposed to. Because of the intricacies of genetics, it may be that this can be achieved relatively quickly (in only a couple of generations, if you wisely start with goldfish that are already on the light side) or it may be (at much more likely) that you would need a very stringent breeding program to achieve a breed of goldfish that is relatively unaffected by diet of light exposure, in the sense that if you stay clear of very carotenoid-rich food and high light exposure, you usually get entirely white goldfish. I should also be noted here, that there is a different between selection for a certain trait (e.g. lack of carotenoid pigmentation) and no selection against that trait: even if carotenoid colouration is no longer required (e.g. no bright light and no role mate attraction), that trait may still remain in the population, either because it is neither positive nor negative with regard to survival or reproduction, or because the mechanism behind carotenoid allocation in intertwined with other mechanisms that are positively selected for (in which case carotenoid colouration is just 'long for the ride'). Only traits that are (practically) neutral with regard to survival and reproduction may nevertheless change over time/generations (a process called genetic drift)

To summarise, carotenoid based pigmentation is a rather complex phenomenon, that can potentially be influenced by a lot of factors, either environmental, genetic or evolutionary. Although it's as such a very interesting topic, it's therefore also relatively difficult to apply to your own goldfish, although general rules can be applies to maximize the chances of your goldfish's colouration becoming what you want it to be.

Excellent post by Erinaceus!

The color of goldfish is environmentally influenced, light being the most important factor: fish raised in a dim environment (such as deeper ponds, ponds with dirty water, rivers, etc.) develop (and retain) pale coloration, whereas fish raised in a bright environment develop brighter, saturated colors. Diet also affects color.

Scientists have identified two types of color changes in fish: physiological and morphological. Physiological color changes are due to the spreading out or aggregation of chromatosomes. When the chromatosomes are spread throughout the cell, the color is more pronounced to the naked eye. However, when the chromatosomes aggregate in the center of the cell, the color is muted or not visible. Morphological color changes, on the other hand, are due to a change in the number of chromatophores. So a fish that loses a number of melanophores will appear lighter, and a fish that gains melanophores will appear darker. Physiological color changes can become morphological color changes over time. For example, a fish that is kept in a tank with a dark background and dark rocks will become darker, initially because of movement of melanosomes in the already existing melanophores. However, if enough time goes buy, the fish will start to produce more melanophores and then the color change is considered morphological.

The common phenomenon of black goldfish turning orange or young goldfish losing black markings as they grow is an example of a morphological color change. As the fish mature, they lose melanophores in a process called apoptosis. Apoptosis is directed cell death, or cellular suicide, and is an important phenomenon in many aspects of development. However, the exact molecular cues that tell a cell it's time to die are still very mysterious. In addition to apoptosis, goldfish that lose black coloration are also suppressing the birth of new melanophores. The loss of melanophores reveals the other pigment cells present in the skin. The type and extent of color change a young fish will go through depends on their individual genetic makeup, and there is a lot of variation between individuals! Some fish even go through a second color change from the destruction of xanthophores (red pigment cells).

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