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

[thebiggerthebetter]

Jur's natural habitat is pretty murky and muddy and dark (deep water) to start with. And then it hunts at night. This makes me very unsure on how the colors play into this scheme. Seems, the colors should not matter at all. Brachies have an exceedingly poor eye sight as if almost not needing it. So they'd tend not to notice each other by color, which throws out rivalry and courtship as causes behind having the colors or the mood-induced color changes. This could only leave rivalry with non-catfishes with good eye sight, e.g. cichlids, and camouflage purposes which two would appear to be mutually exclusive. So here, I am at a dead end again.

Another wrench in the wheel is excitement versus stress. Excitement of courtship and stress of a fight may have a differing effect on mood-dependent coloration as these are the opposite moods, I'd think, even though in both cases the animals hormones etc. are at their peak function. Different hormones or their concentration in the blood.

 

[Chicxulub]

All good points my friend. I was under the impression that these guys lived in clear but tannic waters. Am I correct in understanding that they live in silty water?

I suppose that the only thing left for me to do at this point is acquire one and begin testing on it. This is on my list of things to do once I'm in California.

 

[Empyreal]

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" ....?

It is possible that the vertical barring in date is used as a camouflage technique, explaining why stressed days may show the classic "wanted" barring. In natural environmental stress would questions the color change response for survival? Great thread btw

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[Chicxulub]

It is possible that the vertical barring in date is used as a camouflage technique, explaining why stressed days may show the classic "wanted" barring. In natural environmental stress would questions the color change response for survival? Great thread btw

Sent from my SM-G386T using MonsterAquariaNetwork App

That actually makes a lot of sense, IMO.

 

[thebiggerthebetter]

... I was under the impression that these guys lived in clear but tannic waters. Am I correct in understanding that they live in silty water?...

I was going off a general premise that Amazon is pretty muddy. The vast swampy areas of the Amazon before it hits the Atlantic are clear of particulate because the water flow is almost unnoticeable and dirt settles but the water is black and hence nothing should change (in theory) from my above consideration. The optical density (opacity) of black water is probably not that different from that of the muddy waters up the river.

Also, my impression is that jurs occur widely throughout the Amazon and Orinoco basin in Peru and Brazil. http://www.planetcatfish.com/common/species.php?species_id=566

 

[thebiggerthebetter]

The more I think about this, the more I realize I need to read up on how fish manage their coloration. I am clueless. Anyone knows of a treatise on the topic?

If Rob's premise of a relaxed and, hence, drab-looking jur is taken as a valid starting point, then maybe this is simply their basic, camouflaged coloration. The colors may then come through when it is stressed by a rival in close contact (as opposed to using bright colors to get spotted by a rival from a distance which is moot in muddy and dark waters) or in a different stressful situation (e.g., being caught) and/or it is courtship time and the courtship is happening in seasonally-flooded forests and plains where the water should be ~ static, shallow, and clear and, hence, the colors of use and visible.

 

[Chicxulub]

Your comment about learning about this has prompted me to read up on how and why fish can change colors and how this would affect a jur.

Based on what I've read, the color control mechanism in teleosts is controlled by the pituitary melanophore aggregating hormone (1). The fishes likely use their parapineal organ, which is photoreceptive (3) and used in the fish's determination of light/dark circadian rhythms, to determine the ambient lighting of their surroundings. By doing so, it triggers an involuntary reaction in the fish to control the expression of darker colors via melanin through the MAH released by the pituitary. When the fish is in a darker area, the pituitary glad releases more of the MAH, causing the fish to flush more darkly. When the fish is in a lighter area, it stops producing MAH, which causes the fish to stop expressing its melanophores in areas (2) that can be controlled by the hormone. The authors of (2) also stress that the fish's color expression can be affected by things such as stress and diet.

As such, we can draw the conclusion that with these flash zebras, the only place in which the MAH controled melanophores are located are in the stripes. When the fish is bland and drab looking with poor striping, it is having an involuntary reaction to its environment causing the release of the MAH hormone, which causes melanophores to darken. When the fish is in a bright area, or is stressed or otherwise excited, the supply of MAH is decreased which causes the fish's melanophores to lighten. Since the MAH controlled melanophores appear to only be in the 'stripes', which is why we see what we do.


1- Jain, Bhargava. (1978). Studies on the color-change mechanism in a fresh-water teleost, Nandus nandus. Neuroendocrinology 26(5). 261-269.

2- Leclerq, Taylor, Migaud. (2009). Morphological skin colour changes in teleosts. Fish and Fisheries 11(2). 159-193.

3- Hoar, Randall. (1970). Ontogeny and Structure of the Pineal Organ. Fish Physiology 4. 92-108.

 

[thebiggerthebetter]

Thanks, Rob! Just to point out the obvious - what you cited are some of the biochemical processes and you worked them into your conjecture (that is they neither support nor point away from your conjecture) but it is an excellent starting point for me, for one, to read more.


"The fishes likely use their parapineal organ, which is photoreceptive (3) and used in the fish's determination of light/dark circadian rhythms, to determine the ambient lighting of their surroundings." This refers to the what's commonly labeled as the third eye, right?

 

[Chicxulub]

Thanks, Rob! Just to point out the obvious - what you cited are some of the biochemical processes and you worked them into your conjecture (that is they neither support nor point away from your conjecture) but it is an excellent starting point for me, for one, to read more.

It may be a bit of a stretch in that I plugged in the gaps because I couldn't find a published article that says exactly what I'm looking for, yes. However, three indisputable facts remain: the light/dark color expression of fish is controlled involuntarily by hormones, that expression of the hormones is determined by their environment, and the fish uses it's 'third eye' to determine light/dark gradients.

At this point the only thing left to prove to make this academic is proving the distribution of melanophores vs. normal pigmentation in Brachyplatystoma juruense.

How the hell am I going to do THAT?

"The fishes likely use their parapineal organ, which is photoreceptive (3) and used in the fish's determination of light/dark circadian rhythms, to determine the ambient lighting of their surroundings." This refers to the what's commonly labeled as the third eye, right?

Yes, in tetrapods it would be called the parietal eye. Same thing, different name in fish (for no good reason that I can determine).