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Hi all,

which observed weight loss in these panaques when fed a wood-only diet. If the species identification is correct, these fish are natural wood eaters and not primarily algae eaters. Considering this, then fish in captivity which get fed an algae-only or algae- and wood-diet are probably getting a nutrient-rich diet, relative to what they get in nature. And if we work on the assumption that fish in nature are at least satisfactorily nourished (since they are growing and reproducing), then this would mean fish in captivity should experience greater than normal body growth on the algae diet. As a result, if we then put them on a wood-only diet, I can imagine that there would be a natural metabolic contraction, with an associated weight-loss, or at least serious slowing of growth rate, on this nutrient-limiting diet. This would create the appearance, in the data, that that these fish are not adapted to survive exclusively on a wood-only diet; but it might simply be that their bodies are realigning with a more natural, balanced metabolism and growth rate

It will be interesting to hear what Ryan says, but I think that these are reasonable assumptions.

I also think that not all wood is equal, by this I mean that the heart wood of trees may be fully lignified (with an extremely high carbon to nitrogen ratio), but that any sap wood eaten by the fish would have more available nutrients present.

Again just a hunch, but there is also the microbial content of the wood to take into account. It may be that the combination of the fishes nitrogen fixing/cellulose degrading gut microflora, and the small addition of available carbohydrates & nitrogen from fungal hyphae etc in the wood, tips the nutrient balance in the fishes favour.

I'm not a microbiologist, or a fish physiologist, but I've always thought that it would be surprising if the only adaptation to wood eating that these fish had developed was their extremely modified dentition.

I've had some correspondence with Joy Watts (and with Donovan German), and she told me that the method of preparation of the gut was important. The reason for this was that, rather than being in a specialized structure, the nitrogen fixing microbial assemblage etc was occurring in a mucus layer lining of the gut.

More details are in this thread <Panaque gut microbes http://www.planetcatfish.com/forum/view ... 4&p=268294>.

cheers Darrel

if we work on the assumption that fish in nature are at least satisfactorily nourished (since they are growing and reproducing), then this would mean fish in captivity should experience greater than normal body growth on the algae diet. As a result, if we then put them on a wood-only diet, I can imagine that there would be a natural metabolic contraction, with an associated weight-loss, or at least serious slowing of growth rate, on this nutrient-limiting diet

This is great point. Often for these experiments we will maintain the fish on mixed diets (wood, algae wafers, hearts of palm, etc...) for several months before switching them to a wood-only diet. Every time I have dissected a fish that was grown on a mixed diet their GI tract was almost completely covered with adipose tissue. Little or no adipose tissue was observed in fish that are switched over to wood-only diets. This weight loss may be due in part simply to loss of this tissue.

In regards to the possibility of the counter current exchange of the GI tract. It is definitely exciting to think about. We do not have any evidence that this is occurring but we also haven't investigated it. Through dissection though it is clear that the proximal and distal intestines sit next to each other in the body cavity. Furthermore they seem to be attached to each other by a thin membrane. This membrane is easily pulled apart with forceps, but it is substantial enough to keep those regions joined as the GI tract is unfurled.

still, I wonder the nitrogen binding takes place in the gut. That is, after the food-mass has passed the stomach, which is (at least in mammals) the place where most of the protein downgrading takes place. Bacteria living in the gut will never enter the stomach – therefore I wonder where these bacteria will be processed

A paper by German (2009) actually showed that aminopeptidase activity is highest in the distal parts of the intestines for P. nigrolineatus (~6x higher activity than the foregut). However, as far as I know, nobody has looked at the stomach explicitly. Since digesta isn't retained in the stomach for any extended time (total gut transit is only a few hours) it would make sense that most protein digestion wold be occurring in the intestines.

An interesting next step might be to make these comparisons across the wood eating genera of loricariidae. In the Rio Tinaco, Venezuela I collected wood eating Panaque (P. nigrolineatus sensu stricto), Lasiancistrus, Cochliodon, and Panaqolus. Why four wood eaters in one fairly minor river? Is each somehow specialized to allow all four spp to coexist without competing?

Ryan, it may interest you to know that the two most widely used common names for P. nigrolineatus in Venezuela are "comacanoa" (canoe eater) and "runacanoa" (canoe destroyer) for their propensity to eat holes through dugout canoes. I have heard similar names are used for Panaque throughout Amazonas (Colombia, Peru, Ecuador, and Brazil) as well.

-Shane

That's really interesting. I have heard stories about how the locals use this behavior to catch the fish. They will go out in their dug-outs and wait to hear for the rasping of catfish. They would then reach in and grab them with their hands. Never seen it done though.

Bas Pels wrote:Still, I wonder the nitrogen binding takes place in the gut. That is, after the food-mass has passed the stomach, which is (at least in mammals) the place where most of the protein downgrading takes place. Bacteria living in the gut will never enter the stomach – therefore I wonder where these bacteria will be processed.

Rabbits eat their own faeces in order to benefit from the bacteria in their gut – but as far as anyone knows, Panaque do not, and I don’t think their mouths are capable of doing this.

Obviously it could be Panaque has changed the order of processing – for a wood eater, having a stomach in the traditional sense (a place to digest protein) will not make sense – and having the right kind of protein in the last part of the gut would certainly make sense – but that would imply these proteins would have to be found.

Perhaps these are even very interesting – most likely the Panaque gut will never become as acidic as a stomach does – if it did, anatomical evidence (the special lining) would most likely been found.

mcdonal1 wrote:it would make sense that most protein digestion wold be occurring in the intestines.

Hi Bas Pels and Ryan,

I was following up on this issue and I came upon this title: Mansilla, W., Columbus, D., Htoo, J. K., & de Lange, C. F. M. 2013. Urea nitrogen absorbed from the hindgut is used efficiently for body protein deposition in pigs fed a diet deficient in non-essential amino acid nitrogen. Energy and protein metabolism and nutrition in sustainable animal production, 134, 413-414. Alas, I don't have access to this work, but the abstract is intriguing:

Abstract
The absorption of nitrogen (N) from the hindgut of monogastric animals is thought to be of little value for supporting body protein synthesis. However, N that is absorbed from the lower gut, largely in the form of ammonia, can be used for synthesis of non-essential amino acids (NEAA) or converted to urea. The latter can be excreted in urine or recycled into the upper gut and contribute to microbial-produced amino acids that can be of benefit to the host (Fuller, 2012). The objective of the present experiment was to explore the efficiency of using N absorbed from the hindgut for body protein deposition in growing pigs fed a diet deficient in NEAA-N.

A related article (the Masters thesis by the lead author) can be found here: Non-Protein Nitrogen is Used Efficiently for Improving Protein Deposition and Feed Efficiency in Growing Pigs

Abstract
Nitrogen (N) absorbed by the lower gut (caecum and large intestine), primarily in the form of ammonia, is generally considered to be of little nutritional value for growing pigs. The main objective of research presented in this thesis was to explore the effects of providing nonprotein N (NPN) on N retention, urea kinetics, activity of key liver enzymes, and growth performance of pigs fed diets deficient in non-essential amino acid N (NEAA-N). Urea-N infused into the lower gut increased N retention, with an estimated efficiency of 96%. Whole body urea flux and urea recycling into the gastro-intestinal tract were not affected by urea infusion into the lower gut. When feeding growing pigs NEAA-N deficient diets, feed efficiency increased linearly with level of dietary supplementation with ammonium salts. These data support that NPN can be efficiently used for improving N retention and feed efficiency in pigs fed diets deficient in NEAA-N.

mcdonal1 wrote:In regards to the possibility of the counter current exchange of the GI tract. It is definitely exciting to think about. We do not have any evidence that this is occurring but we also haven't investigated it. Through dissection though it is clear that the proximal and distal intestines sit next to each other in the body cavity. Furthermore they seem to be attached to each other by a thin membrane. This membrane is easily pulled apart with forceps, but it is substantial enough to keep those regions joined as the GI tract is unfurled.

Mansilla's statement that ammonia from the lower gut can be converted into urea and then "recycled" into the upper gut to be used for microbial amino acid production makes me think again of a possible countercurrent circulation pattern (or maybe not exactly countercurrent; maybe just crossing past, like the distal convoluted tubule of the mammalian nephron crosses the efferent arteriole in the kidney, forming the juxtaglomerular apparatus). I wish I had a better picture in my mind of the specific arrangement of the gut in panaques, with the reversing direction of the gut pathway and the potential interaction that might be created between microbes in different sections of the gut as the wood is metabolized.

Before now, I've never heard of vertebrates using ammonia or urea from the diet as a way to boost bodily protein levels, so this is most interesting.

Cheers, Eric

While there are some slight differences between pigs and Panague, this could be quite an interesting route for obtaining proteins.

Obviously, the first question would be the necessary anatomic requirements, and then the fysiological adaptations.

Thanks, Eric

Yes, slight.

UPDATE: I've been speaking with Jay Nelson. He was able to compile a list of the fish purchased (in some cases, with source companies and locations) for their research and also a list of publications and presentations which resulted from these purchases. Here is the information he provided me, as written by Jay (*Thank you, Jay Nelson):

4/07: East Coast Zoologicals,

L027

Rio Xingu,

Kulp, Smoot abstracts were with these fish:

• D. Smoot, R. Kulp, J. A. Nelson and J. E. M. Watts. Microbial diversity in the gastrointestinal tract of wood-eating catfish. National Conf. on Undergraduate Res. April.10-12th, 2008 Salisbury University.
• R. Kulp, D. Smoot, J. A. Nelson and J. E. M. Watts. Production of cellulolytic enzymes by a microbial community isolated from a wood-eating catfish gastro-intestinal tract. National Conference on Undergraduate Research. April.10-12th, 2008 Salisbury University.
• D. Smoot, R. Kulp, J. A. Nelson and J. E. M. Watts. Microbial diversity in the gastrointestinal tract of wood-eating catfish. Minorities in research Science Conference. Sept.14-15th, 2007 Baltimore Convention Center.
• K.D. Nguyen, J. A. Nelson and J. E. M. Watts. RFLP analysis of microbial diversity in the gastrointestinal tract of wood-eating catfish. Towson University ASM MD Branch Meeting June 2007 University Baltimore.
• Smoot, D., N. M. Mohamed, J. A. Nelson, H. J. Schreier, and J. E. M. Watts. Investigating the Microbial Communities Associated with Xylophagy in the Gastrointestinal Tract of Panaque nigrolineatus. American Society for Microbiology, General Meeting, Abstract N-174, 2008.
• Smoot, D., R. Kulp, N. Mohamed, J. A. Nelson, H. J. Schreier, and J. E. M. Watts. Microbial communities associated with different regions the gastrointestinal tract of Panaque nigrolineatus, a xylophagous catfish. Twelfth International Symposium on Microbial Ecology, August 17-22, 2008.

4/08: East Coast Zoologicals, Rio Caguan, Caqueta, Colombia-

My graduate student Mickey Dehn ordered the following from Aquascapes, I found this information in his notes.

6/30/2009 Aquascapes, Rio Negro region, Peru
10/22/09 Aquascapes,

L190

, no region,
12/03/09 Aquascapes,

L190

, no region,

• Dehn, A. M. and J.A. Nelson. (2010). Ever eat a palm tree? Growth, histology, and digestive physiology of a wood-eating catfish, Panaque nigrolineatus. 2010 Joint Meeting of Ichthyologists and Herpetologists, Providence RI.

5/02/10: Aquascapes,

L190

, no region, -Ryan McDonald used : Don Stewart comments:

HI Jay, No that is not titanicus in the picture -- it is another new species that gets even bigger. 'Titanicus', however, is in the manuscript in press along with a third species from southern Brazil that looks like nigrolineatus -- but titanicus will appear with a slightly different name. P. nigrolineatus will be restricted to the Orinoco basin, and the 'nigrolineatus' studied by Hiro is another new species not included in our paper. That is being described in a follow-up paper by a Brazilian colleague.

This group is complex with more new species awaiting discovery/description, but as the newspaper article notes, they are hard to catch -- so small samples in museums and striking morphological allometries make it difficult to understand geographic variation. In this new paper, we re-describe the three previously known 'large panaques', so this should open the door to new discoveries. Cheers, Don

• McDonald, R. C., H. J. Schreier, J. A. Nelson, and J. E. M. Watts. Analysis of 16S rRNA genes from a catfish (Panaque nigrolineatus) gastrointestinal tract reveals highly specialized xylan- degrading microbial populations indicative of a xylophagic dietary strategy. 111th Meeting of the American Society for Microbiology, May 5-11, 2011, New Orleans, LA.
• McDonald, R. C., H. J. Schreier, J. A. Nelson, and J. E. M. Watts. Analysis of 16S rRNA genes from the alimentary tract of the wood-eating catfish Panaque nigrolineatus reveals xylan- degrading microbial populations consistent with a xylophagic dietary strategy. Society for General Microbiology, April 11-14, 2011, North Yorkshire, UK.

7/1/11 East Coast Zoologicals,

L191

claim Colombia. Ryan McDonald also used

Both H. Nonogaki & D. Stewart identify as

• Nelson, J.A., K. McHenry and D. Richards. “INTESTINAL FREE FATTY ACID PRODUCTION BY WATER BREATHING VERSUS AIR-BREATHING PANAQUE NIGROLINEATUS (LORICARIIDAE), A TROPICAL WOOD-EATING CATFISH” Int. Congress on the Biology of Fish, July 2012, Madison WI.

These would most likely be the ones in the recent publication by Schreier, McDonald and company.[/color]

Cheers, Eric

Also, Jay Nelson gave us an invitation: He still has many of the fish, so if anyone who is knowledgeable about these fish is interested in coming to his lab to examine the fish in order to make a more definitive ID, Jay says we're welcome to come and do so!

Cheers, Eric

Where is the lab?

Jools

Jools wrote:Where is the lab?

Dr. Jay Nelson,
Department of Biological Sciences
Towson University
Towson, Maryland USA 21252
http://pages.towson.edu/nelson

I'd seen that before, my brain being dull. There are lots of fish keepers in that area and a Planet folks too. I reckon someone would be able to take pics at some point. But even a smartphone pic would probably suffice forID.

Cheers

Jools

Thanks for you investigating, Eric Like Jools said, a photos would be enough, especially one of the mouth/teeth.

Hello friends!

At first, sorry my English in advance. I hope you will be able to understand
I'm not a scientist, too; I have an education in biology (ichthyology especial) in my background but I have had a loooooong pause and I never really worked in this area. So, my opinion may be just a "semi-educated speculation". But...

What about the weight loss at the wooden diet.
What kind of woods these fishes was receiving?
In the natural habitat, I believe that woods-eaters have unlimited source of woods. And I believe that, in this situation, they eats not exactly WOODS - but only a surface layer of woods, softened and partially destroyed already with fungi, bacterias and algas - so it should not be a clean woods but a rich "cocktail" of partially destroyed woods, bacteria, fungi and algas, which contain alot of protein and other supplements, maybe richest by protein than a regular planted foods. In a real life they just have no needs to eating of under-layers of hardwoods, because they can migrate to a neighbor places, till a cleaned surface will be "restored" - or destroyed - enough to consumption.

If I right, in this situation bacterial digestion of woods may play just a very tiny role in a "energetic" feeding and may working more for help to eliminate a "ballast" of woods, consumed as a side-effect; and some additional benefits by providing some supplements like vitamins etc. If in a laboratory they received just a not sufficient amount of woods, surface cannot be able to be prepared properly by bacteria and fungi, and fishes eats just a clean woods which is not their natural food, and lose their muscle mass, of course...

Hi all,

Krakozawr wrote: What about the weight loss at the wooden diet.
What kind of woods these fishes was receiving?
In the natural habitat, I believe that woods-eaters have unlimited source of woods. And I believe that, in this situation, they eats not exactly WOODS - but only a surface layer of woods, softened and partially destroyed already with fungi, bacterias and algas - so it should not be a clean woods but a rich "cocktail" of partially destroyed woods, bacteria, fungi and algas, which contain alot of protein and other supplements, maybe richest by protein than a regular planted foods. In a real life they just have no needs to eating of under-layers of hardwoods, because they can migrate to a neighbor places, till a cleaned surface will be "restored" - or destroyed - enough to consumption.

If I right, in this situation bacterial digestion of woods may play just a very tiny role in a "energetic" feeding and may working more for help to eliminate a "ballast" of woods, consumed as a side-effect; and some additional benefits by providing some supplements like vitamins etc. If in a laboratory they received just a not sufficient amount of woods, surface cannot be able to be prepared properly by bacteria and fungi, and fishes eats just a clean woods which is not their natural food, and lose their muscle mass, of course...

That would be my suggestion as well, "not all wood is equal".

If you look on page 2. of this thread there are links <"http://www.planetcatfish.com/forum/view ... 4&p=268294"> & <"http://www.planetcatfish.com/forum/view ... an#p241856"> to some earlier discussion on this with Dr Donovan German <"http://german.bio.uci.edu/Research_1.ht ... ecology_of"> as well as to the Towson University papers <http://pages.towson.edu/nelson/Panaque/panaque.html>.

cheers Darrel

Thank you for links Darrel, this is a direct link which mentioned exactly what I mean: http://www.planetcatfish.com/forum/view ... an#p241856

All wood is equal (more-less, if we will forget about tannins and other supplements) - this only a cellulose at least; but not a wood is an energy source for fishes.

It could be Krakozawr was thinking of this: Wild fish, caught and brought to the USA might not be the same as they originally were

It could be bacteria have entered the gut, which was vulnerable because it was empty. We do know Otocinclus can have their guts infected because of being empty, why not Panaque as well.

If this was not Krakozawr's question, his posting made me think of it. Therefore I think he deserves any credit.

I think it is a good question, but if anyone would be offended by it, I'm afraid I'm to blame for putting it this bold.

Bas Pels wrote:...Wild fish, caught and brought to the USA might not be the same as they originally were

It could be bacteria have entered the gut, which was vulnerable because it was empty. We do know Otocinclus can have their guts infected because of being empty, why not Panaque as well.

It sounds like you should develop a new product - probiotics for panaques! In truth, maybe it's not a bad idea. We should encourage Allen Repashy to get on this - maybe he can develop a sawdust-based gel or paste with probiotic microbes in it, essentially aufwuchs in a tube.

bekateen wrote:

Bas Pels wrote:...Wild fish, caught and brought to the USA might not be the same as they originally were

It could be bacteria have entered the gut, which was vulnerable because it was empty. We do know Otocinclus can have their guts infected because of being empty, why not Panaque as well.

It sounds like you should develop a new product - probiotics for panaques!

f2a93c0d69416411bc76722fe333fbfa.jpg

In truth, maybe it's not a bad idea. We should encourage Allen Repashy to get on this - maybe he can develop a sawdust-based gel or paste with probiotic microbes in it, essentially aufwuchs in a tube.

I believe that just a little detritus from a healthy tank wit a same /similar species should be OK
By the way, I don't think that it will be so easy to kill all symbiotic bacteria in a digestion tract of a live fish (even with antibiotics) at all, fish should be dead faster. Bacteria's population should be able to restore when environment will be normalized, I believe.

Yes, I agree. I didn't mean to suggest that all captive fish, especially those following treatment with antibiotics or following the stress of importation, etc., would be devoid of gut microbes and incapable of reconstituting a healthy gut balance. But rather, it's been my experience that some species are more sensitive than others in terms of dietary health, and perhaps such a food supplement could be used to "promote" health rather than actually "create" health in captive fish (I'm not exactly sure what that phrase means, but it sounds good to me, anyway); this is related to what I was describing earlier in this thread with my "apartment building" analogy (http://www.planetcatfish.com/forum/view ... nt#p286915). Of course, the use of probiotics in humans has questionable value according to some doctors and scholars, myself included. But there are definitely times and people who benefit from such nutritional supplements, IMO.

Cheers, Eric

Alas, my suggestion was read precisely as I did not intended it.

I was not afraid bacteria might have left the gut, but I thought they might have entered it.

It could be the nitrogen fixing bacteria live in wild Panaque in the front of the gut system, but in caught Panaque, due to the lack of food, and the therefore more vulnerable gut, the bacteria could have colonized further parts of the gut

Thus one could find bacteria where they would not be found in the wild

Bas Pels wrote:Alas, my suggestion was read precisely as I did not intended it.

Oh.