Anyone with a Juruense/Flash Zebra want to test a hypothesis?

[Chicxulub]

Tonight I was sitting here wondering why it is that our tank-raised jurs tend to have drab, boring coloring compared to their wild cousins and especially tigrinum. For all the years that I've been familiar with these fish, I've assumed that they are brown/black fish with lighter stripes. It occurs to me now that these fish are in fact light colored and the stripes- expressed by the marking cover gene that can't change color like the rest of the fish- is in fact the dark color.

I was poring over various threads on this forum and pics on google when I noticed a correlation to the fish's color and the place in which they are being kept. I've found that fish that are either very stressed, can't see at all, are in very bright tanks, or are in tanks with a clear back (showing white walls) that we see the best color of the stripes. IF Brachyplatystoma juruense is a light fish with dark markings and IF it can change it's colors like so, so many fisht that we see can also do, this would explain why our fishes that we keep in our tanks are so drab looking. Simply put, they are content and they are showing the same coloring that we'd see in the wild if we saw the fishes in their environment other than just fishing pictures.

I hypothesize that jurs, when freshly caught, show their shockingly beautiful color patterns because they're stressed and NOT colored up. I hypothesize that a juruense kept in either an extremely bright normal tank with a light substrate (and I'm talking stupid bright here, beyond reef tank levels of light, like midday in Florida in summer in 2' of clear water bright) or a normally lit white/light tank, we would see an otherwise drab adult or sub adult juruense look like we see in fishing pictures.

In short, I hypothesize that our fish are always dark because our tanks are dark. What we see on wild fish is stress coloring and to reproduce it, we need a bright tank.

Is there anyone out there with a reasonably large jur who would test this hypothesis?

 

[ichthusfish]

Never thought of it that way but makes sense to me. The ones with a bright coloration that i see on japanese websites tend to be in clear tanks with no substrate and alot of light comming through so i say why not?

 

[thebiggerthebetter]

Good thinking, detective. If one finds a footage of a jur in a natural state in its natural habitat, that would help qualify this hypothesis. It's hard to imagine that no one ever shot a jur underwater in Amazon and it's not available on the net. Or maybe we should ask our friends who either live there and dive/snorkel or go there for diving if they had ever seen one.

In my ignorance, I cannot think of a single case where stress improves fish's coloring. It appears to always be the opposite. But this may be because IDK enough yet.

 

[Chicxulub]

In my ignorance, I cannot think of a single case where stress improves fish's coloring. It appears to always be the opposite. But this may be because IDK enough yet.

It's all subjective, though. The fish has a light colored base with dark stripes. When the fish is happy and healthy, it's base color gets darker. When it's stressed and/or in a bright area, it's base color is lighter.

In most fish, when they are happy and showing their full coloration (darker), it improves their appearance. In juruense, when they're stressed and NOT showing their full coloration, they bleach out and it improves the contrast.

A prime example of this same artifact can be found on the blue catfish, Ictalurus furcatus. Most fishermen, when asked to describe a blue cat, would describe it as having a light bluish grey coloration. This is the fish'es stress color.


(Random pic from Google)

When they're fat and happy in the water, they are a dark cobalt blue that is almost black. Most fisherman aren't even aware of this fact.


(My blue cat Marilyn)

Now, imagine black stripes on both of those fish. Which would have the better contrast? The happy, healthy dark blue one, or the stressed out blue-grey one?

I also think from examining this, that B. tigrinum is likely a black fish with white stripes, which is why they are much more stable. I've noticed that they tend to always have the vivid white stripes with anything from a chocolate brown to rich black base color, which means that they are the opposite of a juruense.

 

[thebiggerthebetter]

Tell me please if I get this right. Also, we are just exchanging thoughts that happen to differ. Not arguing!

CX: The fish has a light colored base with dark stripes. When the fish is happy and healthy, it's base color gets darker. When it's stressed... it's base color is lighter.
TBTB: You propose a jur has a light base + dark stripes. Happy jur = darker shade of base (but also the stripes should darken up). Stresses jur = lighter shade of base (but the stripes should lighten up too). I should note that the shades in the dark/blackish color are by far and large more distinguishable than those in the light/greyish color.

CX: In most fish, when they are happy and showing their full coloration (darker), it improves their appearance.
TBTB: Yes, as the nature intended, I'd guess. I think it'd go against the "biological logic", "bio-logic", that a fish should have better colors when stressed. The color is needed for camouflage, to get noticed by rivals, and to get noticed by the other sex. The washed out color helps run away, be less visible, and escape a dangerous situation.

CX: In juruense, when they're stressed and NOT showing their full coloration, they bleach out and it improves the contrast.
TBTB: I don't see it. I'd think "they bleach out and " worsen the contrast. Greyish base pales and gets whiter while the dark stripes pale and get lighter too. Who wins is hard to say but, as mentioned above, I think the dark areas will lose more darkness relative the gain of whiteness by the light areas.

Crudely, contrast, e.g., in displays, by definition is the ratio of the brightness (say in lumens) of "white" screen divided by the brightness of "black" screen. Prior generation LCD blacks were relatively poor (because the bright white back light is always on and the LCD element struggles to shut it off completely shutting off only ~99.9% of the light) resulting in a contrast of ~100,000 whilst the black of plasma and OLED displays is 10-1000 times better. As the black improves, the contrast asymptotically approaches infinity. The improvements in the white matter quite little as white is already pretty white. So the contrast worsens by far and large when the black loses blackness and gains some whiteness.

CX: A prime example of this same artifact can be found on the blue catfish, Ictalurus furcatus. Most fishermen, when asked to describe a blue cat, would describe it as having a light bluish grey coloration. This is the fish'es stress color... When they're fat and happy in the water, they are a dark cobalt blue that is almost black. Most fisherman aren't even aware of this fact... Now, imagine black stripes on both of those fish. Which would have the better contrast? The happy, healthy dark blue one, or the stressed out blue-grey one?
TBTB: If you paint them on, then yes, you'd be right. But the black stripes won't stay unaffected by the stress and will lose more blackness than the whiteness gained by the base. I think.

CX: I also think from examining this, that B. tigrinum is likely a black fish with white stripes, which is why they are much more stable. I've noticed that they tend to always have the vivid white stripes with anything from a chocolate brown to rich black base color, which means that they are the opposite of a juruense.
TBTB: I think the variations in the shade and hue of the dark areas of a tig has little or nothing to do with stress but with normal bio- and geo-diversity of the species. My tigs and jurs always conformed to what I'm saying here: they looked washed out when stressed, not better by any means of imagination.

 

[Chicxulub]

What I'm driving at Viktor is that I've never really noticed a change in the color of the darker stripes of my jur, only in the lighter stripes. The lighter stripes would vary from very dull and barely visible when she was fat and happy to bright and bold when she was hungry or I had the lights on too long. The darker stripes never seemed to change.

This led me to the idea that the base color of the fish is represented by the lighter stripes, with the darker stripes appearing as the manifestation of a masking gene, a gene which causes a melanistic pattern to be expressed that is separate from the base color. This is consistent with my observations of Ginger in that her darker colors always seemed to stay the same, but the way she displayed her lighter areas could vary wildly based on environment and hunger.

EDIT-

I'd also like to point out another thing I've noticed that supports the idea that these fish are light colored with dark markings. In the tig vs. jur thread that's active right now, mustang93svt posted pics of his successful tig and jur cohabitation. In the first pic when the fish were about a 10" long, the jur appeared to be very dark colored with thin, poorly formed stripes. In the picture posted this weekend, the jur has bold, thick light stripes and indeed, the darker markings are 'fading' in the middle, to reveal the lighter base color. The idea of fading markings with age is more plausible and consistent with other observations IMO than developing more, nicer colors as it gets older.

EDIT 2-

I really wish we could sit down and actually have this as a TALK. You always make me THINK Viktor.

 

[T1KARMANN]

I have been saying the exact same sort of thing in the Datnoid section of the forum for years but it always gets dismissed

I have said the turn stable and unstable could in fact be wrong with indo dats

I found that normally when a indo tiger is stressed it displays black stripes on a gold body basically when it if moved to a new tank or being bullied and when it turns black it is in fact happy

But with jurence flash jurence mainly that yellow gold coloration comes from something it eats in the wild much like the pink colour flamingos get


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[thebiggerthebetter]

What I'm driving at Viktor is that I've never really noticed a change in the color of the darker stripes of my jur, only in the lighter stripes. The lighter stripes would vary from very dull and barely visible when she was fat and happy to bright and bold when she was hungry or I had the lights on too long. The darker stripes never seemed to change... This is consistent with my observations of Ginger in that her darker colors always seemed to stay the same, but the way she displayed her lighter areas could vary wildly based on environment and hunger.

I see. Thanks, Rob. I think I get what you state now - in opposition to the light, the dark does not change or changes only slightly. I think I am a rather careless observer as I cannot recall paying attention to how stress affects differently colored areas on any fish. All I can say is that I have not seen a fish display better looks when stressed but then again I should start paying more attention to that.

I have been saying the exact same sort of thing in the Datnoid section of the forum for years but it always gets dismissed

I have said the turn stable and unstable could in fact be wrong with indo dats

I found that normally when a indo tiger is stressed it displays black stripes on a gold body basically when it if moved to a new tank or being bullied and when it turns black it is in fact happy

But with jurence flash jurence mainly that yellow gold coloration comes from something it eats in the wild much like the pink colour flamingos get

I cannot say much about the dats but I must trust your observation. As for the yellow or gold or orangish colors in a freshly caught wild jur, they disappear in under 5 min and never come back it seems. It is hard to reconcile this observation with the accumulation of pigment derived from food as that would take significant time to be consumed and processed and discarded by the body.

 

[Joao M]

I´ve kept a few (IT´s ) and agree with T1 as regards the Datnoids.

The more "suitable" environment I provided (hidding spots, vertical plants, species tank) the darker they became; when they were in a more stressful environment - with bigger and/or agreesive fish- they got brighter and more colourful.
In fact, their best colours were showed when I had to catch them and they were out of water in a net!

So if this applies to other fish as well, ultimately, does this mean that we need to stress our fish so they look their "best" ....?

 

[Chicxulub]

This is all a subjective issue I believe. I feel that the dats are supporting my hypothesis.

This whole issue comes down to a subjective idea of what looks better. To a human, a high contrast pattern looks better in these fish, so we assume that this must be the relaxed state for the animal.

I suspect that the relaxed state is the more richly pigmented state, the low contrast, mostly dark state.

But that whole line of conjecture is getting away from my original point. It may simply be that the fish are darkly patterned because we as a community like black substrates and black backgrouds combined with moody ambiant lighting.

Getting back to the point, if juruense normally inhabit swiftly flowing waters in the middle of and channel perched up on a log, would it not be reasonable to assume that the tripod on driftwood facing into the current? If so, these fish may or may not, under THOSE comditions, these fish may display he more vivid, high contrast pattern.

The hypothetical hunting pattern would then be displayed when the fish is in something that feels like "open water", a tank with clear sides and no substrate in front of a white wall.

This was what I wanted to test, but I think I may have failed to articulate that clearly in the OP.

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