Have you ever seen Hemiancistrus guahiborum turn yellow like Parancistrus aurantiacus?

[bekateen]

Hi All,

I was just at my favorite LFS today, spying out their plecos and corys.

For several months now, they've had a tank full of about a dozen

Hemiancistrus guahiborum

. When they arrived, they all were small and charcoal colored with spots, the typical juvenile pattern. As they've grown, some have changed to the normal olive color with faded spots typical of adults. This is the same color pattern I see in all of my H. guahiborum which I've had for a few years now (My spotted orange seam plecos: Hemiancistrus guahiborum (L106)).

But what caught my eye was a group of 4-6 individuals that were bold yellow with brown mottling. I initially mistook them for

Parancistrus aurantiacus

. But these fish have orange seams on their dorsal and caudal fins like normal H. guahiborum.

The LFS employees say they haven't added any fish to the tank from more recent shipments, and that all the Hemiancistrus in the tank are from the original H. guahiborum shipment last Fall.

On L-welse.com, there is a page that states this xanthic transformation does occur in H. guahiborum, but I guess it's not very common. What impressed me was that there wasn't just one specimen that transformed, but almost half the tank has changed to the xanthic color pattern. To be careful on vocabulary, these fish are not purely xanthic - they still have some brownish blotches on their bodies. But they are predominantly yellow.

If my tanks weren't full, I would have bought them all. But I left them all in the store.

Cheers, Eric

[bekateen]

Here's a video of the fish. Enjoy:

Yellow/Xanthic Morphs of Hemiancistrus guahiborum (L106)

[Shane]

Eric,
I have seen this before as well and am baffled by it as I never encountered fish with this condition in the wild. I also, over two years in Bogota, saw literally thousands of this sp go through export facilities and never saw a single mis-colored individual.

Now the really strange part is that the only place I have ever seen it is a specific fish store in Maryland. I have seen mis-colored individuals, of several spp including this one, there on multiple visits.

My best guess, and it is only a guess, is that we are seeing a reaction caused by a specific medicine or other treatment. Blind loricariids will often exhibit strange colors because they can not adjust their colors correctly to ambient light or the substrate's color, but I have never seen blind fish take on this mottled yellow and brown appearance.

-Shane

[bekateen]

Thanks Shane. Interesting perspective. I was under the impression that when this phenomenon is observed in an "atypical species," it is just as likely to be in nature as in a store, and that it would be isolated to a single individual. But if you really can find this in groups of fish in a single store, the notion that it would be the consequence of some kind of environmental exposure (meds, food, water contaminant) seems very plausible.

And if that's the real cause, then the fact that there are fish like this is not something really to value, and I wouldn't expect them to produce xanthic fry if you could get them to spawn. (not that the "typical" color morphs are easy to spawn... I haven't seen even one instance of courtship behavior among my group of guahiborum).

As an endocrinologist, I've wondered if this is related to several hormones that affect color in animals: melatonin, melanocyte stimulating hormone (MSH), melanocyte concentrating hormone (MCH), adrenocorticotropic hormone (ACTH, which includes a segment of MSH within its structure), or epinephrine. But I don't have any explanation for how such an effect would be triggered or exactly what was occurring within the fish.

For what it's worth, the xanthic fish did react to my presence, so if their vision is impaired, it's certainly not all gone. On the other hand, maybe they were detecting vibrations and not images as I moved.

Cheers, Eric

[Acanthicus]

Hi

It is very rare that we get to see misscoloured specimens in or from the wild, but it happens. I know of at least Ancistrus dolichopterus and Baryancistrus chrysolomus, as well as partly misscoloured (being in the state of changing) specimens of B. xanthellus, O./S. punctatissimus and P. asurini.

"Medicine or treatment" was one of my initial thoughts too, but the frequency we see this colourchange nowadays doesn't make it very likely to be the reason. Mostly only one or few specimens change, sometimes a whole group does and in few cases all of them change. Always kept in the same tank with identical water parameters. But I agree it could be an immune reaction to something.

They would not produce xanthic fry of course, since they are not xanthic. I wouldn't use the term here to avoid any further missunderstandings. The pictured specimen of G. guahiborum actually produced normal looking fry after the photo was taken, not instantly, but a few months later.

They are also not blind, but perfectly healthy. They change back to normal colouration, change back again and often change back, and back....

[bekateen]

I wouldn't use the term here to avoid any further missunderstandings.

I didn't mean to associate the yellow color change in these fish to classic xanthism, but before posting here I searched several sources to see what I could find in terms of a more accurate term, and to be direct I did not find a better term. I say this because it is unclear to me as to the exact nature of the color change.

Although I study fishes now, I didn't in my early career and education. I am classically trained in amphibian and reptilian physiology, including color change.

Many of the pigment cells of fishes and amphibians are classified as "XXX-phores" instead of "XXX-cytes (e.g., melanophores instead of melanocytes). The difference is that pigment cells called "phores" are able to undergo rapid color modification by moving pigment particles within the cells or by other mechanisms (think of a lizard changing from green to brown) whereas "cytes" cannot (think of a human - we can get more melanin to darken our skin, but we can't flash that dark pigment and make it disappear in an instant).

There are several different mechanisms that can alter the color of these fishes - some include a loss of pigment (e.g., melanin), or a gain of pigment (carotenoids, pteridines, and purines).

Two good reads on the subject are

• Morphological skin colour changes in teleosts (PDF here)
• Rapid color change in fish and amphibians – function, regulation, and emerging applications (PDF here)

I'm unclear on whether the color change in our plecos is due to melanophore cell loss or pigment loss or selective exposure/stimulation of xanthophores, erythrophores, leucophores or iridophores.

This subject seems like it needs more research.

Cheers, Eric

[Bas Pels]

I wouldn't use the term here to avoid any further missunderstandings.

I didn't mean to associate the yellow color change in these fish to classic xanthism, but before posting here I searched several sources to see what I could find in terms of a more accurate term, and to be direct I did not find a better term. I say this because it is unclear to me as to the exact nature of the color change.

If a phenomenon needs a name, but does not have one, anybody can suggest one.

At school I learned LH stands for Luteinizing Hormone, and luteinizing was Latin for yellowing. It works on the rests of the egg cell after ovulation which turn yellow and produce a hormone for the first period of the pregnancy bofore the placenta is made.

If luteinizing means yellowing - that would be precizely what we need. A luteinized fish is yellow after been made (turned) yellow. Someting different from a xantic one.

[bekateen]

If a phenomenon needs a name, but does not have one, anybody can suggest one.

At school I learned LH stands for Luteinizing Hormone, and luteinizing was Latin for yellowing. It works on the rests of the egg cell after ovulation which turn yellow and produce a hormone for the first period of the pregnancy bofore the placenta is made.

If luteinizing means yellowing - that would be precizely what we need. A luteinized fish is yellow after been made (turned) yellow. Someting different from a xantic one.

Exactly. I feel the same. That's why in my OP of this thread, I used the phrase, "Luteinized" with xanthic because I didn't know which word is more appropriate. But xanthic fish are also yellow.

Although to be honest, I'm still struggling to know the difference in this case. Xanthic animals are yellow. If you look up the definition of xanthism in a medical dictionary, there is an expected underlying cause in humans... but I don't clear that it holds true for all animals. And are all xanthic fish born/hatched xanthic? Or can an animal become xanthic midway through life? For examples are

Parancistrus aurantiacus

or

Hypostomus luteus

considered to be xanthic fish? Or are they characterized as something else?

If there is not a specific etiology (=causation) for all forms of xanthism, or at least a specific presentation (=set of symptoms or events/pattern of development or occurrence: e.g., is the animal born with the color pattern or do they change mid-life?), then it doesn't seem appropriate in the case of these fish to rule out the use of the word xanthism.

That's just my two cents.

Cheers, Eric

P.S., A word that sounds similar to "luteinized" is "leucistic." If you look up the word "Leucism," it is a loss of body pigmentation (of multiple colors, not just melanin) and so the animals tend to be white, not yellow. Since leucisms is a genetic defect, it arises from birth/hatching. Clearly leucistic and luteinized are not similar phenomena.

[Bas Pels]

As far as I know, just as an albino does not have black pigment, an xantic animal only has yellow pigment. I thought from birth

The problem is, obviously, an animal can well be genetic programmed to lose it´s pigment, all but the yellow one, after a year. Is it xantic or luteinized?

[Jools]

Just on the other thread in this thread, remember also that odd yellow fish if they survive natural selection will most likely not pass undetected through export selection. They well end up in a different importer/retailer from much of the other catch from that location and will be separated out from the "catch" very early on.

This is why we still see contaminants but not these yellow forms very often. Unless they are relatively common or you're with the fishermen, you'll tend not to see these.

Jools

[bekateen]

Thanks Jools. Of course, that makes sense. In the case of these particular fish, they were "wild-type" normally melanized fish when they arrived.

Cheers, Eric