Panaque/Pleco feeding discussion (split from Science News)

[Suckermouth]

-- MOD EDIT --
This topic is split off from a post in Science News: http://www.planetcatfish.com/forum/view ... 14&t=27372

There are two more posts on the subject of Panaque feeding.
here:
http://www.planetcatfish.com/forum/view ... 14&t=27504
and
http://www.planetcatfish.com/forum/view ... 14&t=27505

Enjoy the discussion!

--
Mats

-- END MOD EDIT --

So one of the things I want to point out is, Lujan looks like he did a rather comprehensive review of the literature of loricariid diet, and only Panaque and Hypostomus cochliodon-group loricariids have been shown to eat wood. He does point out that there are some problems with how this data is obtained, such as the difficulty in identifying food after digestion, the usually collection season (dry season) being a time of little eating in loricariids, and that loricariids push food through their gut at high rates resulting in most specimens having very little food in their guts. However, my point is that there's very little evidence that wood in an aquarium is more than just a nice decoration for growing aufwuchs for loricariids other than the ones I previously mentioned. There's little scientific (vs. anecdotal) evidence to show that any other genera require wood to the extent that people recommend placing wood in loricariid tanks.

For example, in Lujan's descriptions of B. beggini, B. demantoides, and H. subviridis, he points out that these fish were found in/exclusively/most frequently (respectively) among granite boulders and other rocks. Although he also says that P. nigrolineatus is sympatric, the habitat is likely heterogeneous.

On the other hand, it doesn't really hurt to put wood with most loricariids, but I'm not sure if it's as required as some people think it might be.

[MatsP]

This discussion probably belongs somewhere else, but I think that other fish CAN eat wood, and I certainly find that Ancistrus are grazing on the wood in the tank quite a lot. I actually believe that fishkeepers would be slightly better placed to judge this than science (based on your description of the problems with using fish in scientific collections for this purpose).

I'm not splitting the topic right now, but if it starts to get "busy", I'll probably move it elsewhere.

--
Mats

[Yann]

I am not totall agreeing on this!!

Studies has shown that Panaque and Hypostomus of the cochliodon species group have a special bacteria in their guts to digest food but most of all extract nutriments others can't do.

Surely Ancistrus and others probabl eat wood but I think it is unvoluntary, and I would not see the point for a fish to eat something in which he cannot extract a thing ...

Many people have believe Ancistrus and others eat wood, just because their driftwood is getting smaller, but the vastly underestimate the power of water and micro organisms in that process...

Cheers
Yann

[MatsP]

Many people have believe Ancistrus and others eat wood, just because their driftwood is getting smaller, but the vastly underestimate the power of water and micro organisms in that process...

Next time I see lighter scrape-marks where the fish has been scraping off the dark rotting wood, I'll take a photo - and no, there are no panaque in this tank, but the Panaque will show similar scrape-marks. It may well be that they Ancistrus are looking for other things (algae, microorganisms), but I sure see scrape-marks on the wood.

--
Mats

[Yann]

Sure but...
I can see teeth marks on bones but doesn't mean the animal will eat it....


Cheers
Yann

[Janne]

Where I am right now we have around 800 aquariums with 80% plecos, at least 60-70% of these aquarium is every morning the bottom full of waste from digesting wood, no gravel in the tanks and they dont get any food they like so they eat of the driftwood with 100% security. There are no Panaques because they are forbidden to export for the moment, but there is many genus of plecos that eat and shit wood. If all of them would eat the wood if they get properly fed with other food... thats a good question.

Janne

[Suckermouth]

Studies has shown that Panaque and Hypostomus of the cochliodon species group have a special bacteria in their guts to digest food but most of all extract nutriments others can't do.

Actually, this is incorrect... I asked Nathan about this myself. Nathan invalidates Nelson's findings for various reasons that I don't remember. However, it can even be reasoned that Panaque and H. cochliodon do not digest wood through gut bacteria: wood is not retained in their bodies long enough if it were gut bacteria digesting it. By comparison, a termite will retain cellulose in their gut for about a day, as opposed to 4 hours as found in P. nigrolineatus. They merely chew on the surface and pass it through their gut as fast as possible. I don't really feel like re-reading that paper to see where the problem points were, but suffice to say Nathan says this: "...the energy and nutritive value of the wood they consume is largely derived from associated fungi and free monosaccharides and amino acids released during fungal predigestion of the wood."

I don't think this invalidates my questioning wood's importance in the diet of other ancistrines (I'm limiting it to ancistrines as I think people don't really argue wood to be placed with hypoptopomatines or loricariines).

Perhaps other ancistrines can eat wood, but is it so necessary that someone should demand wood be put into a tank with just about any ancistrine? I've seen people get into arguments over it, and problematically there is little evidence that wood is an important dietary element in most loricariids. Is wood consumption the rule or the exception? I hypothesize that wood consumption is exceptional among ancistrines, not a rule. More specifically, wood is likely not a primary part of the diet for species that associate primarily with rocks (ie. B. beggini, H. subviridis, B. demantoides, Hypancistrus, Pseudolithoxus, Lithoxus, Lasiancistrus, Chaetostoma). I don't know about its habitat, but I also wouldn't expect Leporacanthicus to consume wood because of their specialized teeth for carnivory, which is good for speed but not for applying force.

An example of a genus I think might eat wood may be Peckoltia. Many of the Peckoltia have been cited to be found inside hollow logs (although some have also been cited to be found primarily among rocks). Furthermore, with Nathan's findings about jaw angle being associated with increased force for the purpose of wood chewing, it is quite possible that Peckoltia feed on wood. At the very least, because of Peckoltia's preferred association with wood, it'd be good to include wood in their aquarium to better mimic their natural habitat, if not to also provide some form of food. I'm quite curious about P. bachi, as according to Nathan's dissertation it is quite similar to Panaque but its diet has not yet been described.

I just think that the assumed use of wood by most ancistrines is overstated in the face of what I consider to be sparse evidence. On the other hand, I have only kept a few species of loricariids, so I haven't directly observed a diversity of species like Janne has. I could be completely wrong and most ancistrines could very well feed on wood, but from my perspective it remains an open question instead of people simply assuming that most ancistrines utilize wood without evidence to back it up.

As a small disclaimer, I might actually be wrong about many aquarists thinking ancistrines need wood in their aquarium, but I've seen it more than a couple times.

If there's a typo or something confusing, forgive me, it's late.

[Yann]

Hi!!

I think it is more a question of terminology used...

I mainly disagree with the use of the word "eat"... ingest would be more correct....

eat is voluntary while ingest can be both voluntary or unvoluntary...

Surely Loricariidae ingest wood, but like I said it is not in a voluntary way, I think it is because the substrat (wood) the are grazing on, is itself being very slowly desagrated by micro organisms, the Loricariidae just help accelarete the process and unpurposel ingest some wood particules...like Geophaginae would do with sand in their process of food hunt


Hope I made m point a little more clear than in the origin

Cheers
Yann

[Janne]

Perhaps other ancistrines can eat wood, but is it so necessary that someone should demand wood be put into a tank with just about any ancistrine? I've seen people get into arguments over it, and problematically there is little evidence that wood is an important dietary element in most loricariids.

Both yes and no, the main problem is that most aquarist not feed their plecos as they should, wrong type of food or no food at all because they think they can only live on the waste from all other fishes... so, even if wood not is their main source for food it helps them to survive.

Is wood consumption the rule or the exception? I hypothesize that wood consumption is exceptional among ancistrines, not a rule. More specifically, wood is likely not a primary part of the diet for species that associate primarily with rocks (ie. B. beggini, H. subviridis, B. demantoides, Hypancistrus, Pseudolithoxus, Lithoxus, Lasiancistrus, Chaetostoma).

I think it's an exception for most species and something they maybe eat when there is nothing else available both in the aquarium and nature. Genus that consume wood in our aquariums is Ancistrus (even A. ranunculus), Peckoltia, Baryancistrus, Spectracanthicus, Lasiancistrus, Hypancistrus, Hypostomus, Hemiancistrus... and probably some more I don't remember right now.
Leporacanthicus and Pseudacanthicus is very poor wood eaters and their waste is different, but they do shew on wood or the silicon inside the aquarium.

I could be completely wrong and most ancistrines could very well feed on wood, but from my perspective it remains an open question instead of people simply assuming that most ancistrines utilize wood without evidence to back it up.

I think you are correct when it comes to most species, one thing to remember is that there are lots of different Palms growing along the riverbeds, many fall into the river and palmheart is quite good... they use that as trapbait when catching larger Panaque's and if fed in aquarium they consume it in a few minutes and shit over the whole aquarium Feeding Baryancistrus species sweet potatoes and they shit orange ;)

Janne

[MatsP]

Just to "bump" this thread to show that it's moved - as commented in the Science Section, I have split & moved this thread here.

--
Mats

[Shane]

Lujan looks like he did a rather comprehensive review of the literature of loricariid diet, and only Panaque and Hypostomus cochliodon-group loricariids have been shown to eat wood.

True, based on the very limited amount of literature that has been written on this topic. There are many other loricariid genera that "eat" wood. Ounce for ounce,

Lasiancistrus tentaculatus

can down as much or more wood than Panaque. There just have not been any papers written on wood eating among Lasiancistrus.

... so, even if wood not is their main source for food it helps them to survive.

I really agree with Janne here. Wood, whether it turns out to be a main food source or not, clearly plays an important role in the lives of many loricariids. There is a reason that sunken driftwood is the best place to catch many loricariid spp in the wild, why they prefer it over artificial structures in aquaria, why they ingest it, and why some poop it out in amounts that can strain the best filters on the market.
I suspect that the ingestion of wood probably even plays a different role for different spp. i.e. it may provide a critical digestion component in one sp's diet while acting as a trace nutritive source in the diet of a different sp. It would appear illogical to me to assume that it would play the same role in all spp in such a large and diverse family.

With regard to any "argument" over providing wood... that just seems silly. The goal of every aquarist should be to provide their charges with a habitat that best mimics their natural environment. Why refuse to add a natural and major component of their habitat in the wild to the aquarium? Especially when it may actually impact the animal's health.

-Shane

[Suckermouth]

Ounce for ounce,

Lasiancistrus tentaculatus

can down as much or more wood than Panaque. There just have not been any papers written on wood eating among Lasiancistrus.

This is news to me, and breaks my assumptions about this genus (although I admit I'm not all too familiar with Lasiancistrus). Based on jaw angle alone their jaws do not seem optimized for force in the way Panaque jaws are.

There is a reason that sunken driftwood is the best place to catch many loricariid spp in the wild

With regard to any "argument" over providing wood... that just seems silly. The goal of every aquarist should be to provide their charges with a habitat that best mimics their natural environment. Why refuse to add a natural and major component of their habitat in the wild to the aquarium? Especially when it may actually impact the animal's health.

-Shane

I know you have gone collecting, so your experience is greater than mine on that regard. However, a greater proportion of the papers I've looked at that mention loricariid ecology (which I'll admit is fairly limited, and likely not a random sample among Ancistrini) record loricariids being caught among rocks, not wood. Wood is brought up for Peckoltia and Panaque, and "emergent grasses" and such are raised for various hypoptopomatines, but I have seen rock/bedrock as a primary habitat for finding loricariids more often than wood. Certainly, the rivers are heterogeneous habitats with both wood and rocks, but wood isn't noted in the microhabitat that these fishes are found in. I haven't done a comprehensive review of the literature for habitat, but fast-flowing water over rocks is the general loricariid habitat; there are obvious exceptions but wood is not something that is always found with loricariids or even always found with non-carnivorous ancistrines.

I use wood in all of my tanks that have loricariids anyway because of the "couldn't hurt" mentality. I won't go so far as to say that a loricariid will actually require wood as part of the diet (except in the substantiated circumstances of Panaque and similar fish), but I will sometimes note this prevailing aquarist opinion of importance of wood in loricariid diet.

Perhaps I just haven't seen enough notes of people's observations of wood consumption of loricariids in aquaria, which is certainly a possibility, I don't spend all my hours looking at aquarist writing. It's not that I'm sitting in the ivory tower and holding scientific studies to be the only true evidence to make substantiated claims from; I have used aquarist-written articles such as those collected in Shane's World numerous times as a resource. On the other hand, I haven't seen any aquarist articles that list out what specific genera are wood eaters, through their own direct observation or through others, and what genera are not. From my standpoint, it just seems like people have made a big leap from, "oh, certain ancistrines eat wood", to "therefore they pretty much all do."

I suspect that the ingestion of wood probably even plays a different role for different spp. i.e. it may provide a critical digestion component in one sp's diet while acting as a trace nutritive source in the diet of a different sp. It would appear illogical to me to assume that it would play the same role in all spp in such a large and diverse family.

This is a valid hypothesis, to be sure. To go along with that, it is possible that generalists can utilize wood, but may only be able to use it after it has been decomposed more than Panaque and similar wood-eaters which are expressly adapted to feed on wood require. I can believe that many loricariids eat wood, but my problem is making that claim when I really haven't seen any evidence to make this generalization, aquarist-authored articles or otherwise.

Of course, if there's a link that I just haven't seen before that makes a list of wood-eating genera or species of loricariids, I'd looooove to see it.

EDIT: It's not impossible there are species that are specialists at eating wood and there are generalists that may also consume wood, either for nutrition or as a by-product of feeding on aufwuchs. Furthermore, wood may provide a beneficial substrate for aufwuchs to grow on, independent of whether or not the fish actually eat the wood itself, and for that reason wood may be a good addition to any loricariid aquarium, provided it plays this role in captivity as well. Although my initial argument was questioning the dietary requirement of wood, it is apparent now that it is perhaps not as binary as whether or they eat wood or not, which complicates things.

[Janne]

I suspect that the ingestion of wood probably even plays a different role for different spp. i.e. it may provide a critical digestion component in one sp's diet while acting as a trace nutritive source in the diet of a different sp. It would appear illogical to me to assume that it would play the same role in all spp in such a large and diverse family.

I agree, another thought... what about some plecos just use wood or the fibrer's from wood as a "cleaning" mecanism?

What about teeth's? For example, Leporacanthicus seems to have quite delicate teeth's make me think they should broke them if even trying to shew on wood, but they are capable to brake almost any wood or shew away lots of silicon and I mean hard and fresh silicon... without loosing any tooth. The different within this genus is that their waste is more like fine sawdust when in other genus the waste is more compact and unbroken.

Janne

[apistomaster]

I raise Peckoltia fry entirely on supplied food. The wood that is present is mainly for them to use as hiding places.

I put 12 F1 L134 in my wild S. haraldi display tank and they feed mainly on the same foods as I feed the Discus. Outside of feeding time they seem to spend a lot of their time working over the 2 large, smooth branches of wood I used as part of the decor. I don't doubt they are feeding on microorganisms that attach to or grow from the wood to supplement their diet. They keep the wood clean but don't appear to actually eat it. I wouldn't expect this species to eat wood.

In my other tanks with wood, especially locally collected "soft" hard woods, the wood rots away over the years regardless of the presence or absence of any plecos or Loricariidae. Any suckermouth catfish present no doubt hasten the loss of mass just doing their normal search for edibles. The common Ancistrus cf. cirrhosus I have spread around as algae eaters probably do more than any of my more carnivorous sucker mouths to hasten the decomposition of the softer wood pieces I use than any other species I keep. I don't have any species known to feed on wood since I sold my L204 Panaques.

[racoll]

There is an article on wood eating in Panaque by D.P. German in this months PFK.

There are also the two studies here and here in the Journal of Fish Biology by J.A. Nelson on Panaque.

Some of that information can be found here, but please PM me if anyone wants the original papers.

[Suckermouth]

racoll,

German has also published two papers with links in Science News. I don't have a PFK subscription, but it's interesting that he's also writing from an aquarist perspective. I'm sure it's an interesting read.

[racoll]

German has also published two papers with links in Science News.

Yes, and seeing those, along with the recent discussion was the reason I posted links to the Nelson papers.

I don't have a PFK subscription, but it's interesting that he's also writing from an aquarist perspective. I'm sure it's an interesting read.

If I get a spare five minutes I will photocopy it for you. PM me your email address.

[DJ-don]

I suspect that the ingestion of wood probably even plays a different role for different spp. i.e. it may provide a critical digestion component in one sp's diet while acting as a trace nutritive source in the diet of a different sp. It would appear illogical to me to assume that it would play the same role in all spp in such a large and diverse family.

I agree, another thought... what about some plecos just use wood or the fibrer's from wood as a "cleaning" mecanism?

What about teeth's? For example, Leporacanthicus seems to have quite delicate teeth's make me think they should broke them if even trying to shew on wood, but they are capable to brake almost any wood or shew away lots of silicon and I mean hard and fresh silicon... without loosing any tooth. The different within this genus is that their waste is more like fine sawdust when in other genus the waste is more compact and unbroken.

Janne

i agree on this. personally i think wood is not really something that these fish eat.
e.g. humans ingest vitamin tablets detox and such
loricads probably just use wood as a "vitamin/mineral etc"
but because im 14 i have limited knowledge on fish and cant do marine bioligy until im in year 10

[Shane]

Milton,
You raised some good points above and I want to spend adequate time attempting to answers those questions that I am able to. This week just got away from me with my daughter's birthday and other goings on. Consider this a place holder.

As to "eating" things that provide zero nutritional input to the body, I reminded of the too many zero calorie diet sodas I down every day.

-Shane

[DP German]

Hello,

I thought I might jump in on this conversation, since it's about wood-eating catfishes. I have launched a "diatribe" response to the PFK interview. You can read it at http://pd.bio.uci.edu/ee/dgerman/PFK_response.html

As Yann pointed out, there is a difference between "eating" and "digesting" wood, even for Panaque. Because I am friends with Dr. Nelson, I don't want to get into the shortcomings of the previous work here on a forum. However, if you want to discuss them (as well as the other isotopic data I haven't published yet), shoot me an e-mail (dgerman@uci.edu) and we can skype about it.

Hope all are well.

Cheers,
Donovan

[Suckermouth]

Oh wow, thanks for the link! That surely gives us more to discuss about. I really need to get around to reading your papers, though, there seems to be relevant information I'm missing.

[Suckermouth]

After skimming over German's papers, I've think I have some new thoughts.

Both Panaque and Pterygoplichthys lost weight under a diet solely of softened wood (similar to what they find in the wild). I was surprised Panaque actually require wood that can be broken off by hand, rather than harder woods. In any case, what the results of the experiments show is that these fish require more than wood. This makes sense, as cellulose is high in carbon, but low in nitrogen. Nitrogen may come from detritus or some other source, but it certainly doesn't come from wood. What this means is that even wood specialists get food from more than just wood itself. However, wood is certainly an integral part of the diet of wood-eaters.

On the other hand, given that the digestive tracts of Pterygoplichthys and Panaque are similar, then it is reasonable to assume that as long as the wood has degraded to the point that Pterygoplichthys or other detrivores/generalists can ingest, that they can actually get some of the products of microbe degradation. Because H. cochliodon, Pterygoplichthys, and Panaque represent three separate tribes and that their digestive tracts are similar and unspecialized, it's reasonable to assume that unspecialized members of all three tribes should be able to consume wood. This, of course, goes against what I was thinking earlier in this topic, but now that I'm seeing data to back up this idea it doesn't seem so unreasonable.

How do these findings apply to the aquarist?

Although wood is a natural constituent of the diet of Panaque and H. cochliodon fishes, the wood these fish were found to feed upon in the wild and the wood used in this study was soft wood that could be broken with one's fingers. This contrasts greatly with mopani wood. Malaysian wood is also not this soft for quite some time. I'm not sure how long it would take for either of these woods, or others, to be degraded. Thus, it's difficult to say how long it'll be after someone puts a piece of dry wood in their tank that a loricariid should be able to eat any of it.

Also, German debunks the argument that Panaque feed on palm, having never seen Panaque feeding on palm. Although, he notes they fed rather indiscriminately on species wood, so this is good news from an aquarist's standpoint as they can provide whatever species they want, provided that the wood is properly waterlogged and degraded. Wood in this state is pretty much just the cellulose and lignin, losing traits that are species-specific such as tannins. The effect of tannins on loricariids, which is definitely present in fresh wood, is still unknown. Most loricariids, including wood-eaters, originate from clearwater as opposed to blackwater. I wouldn't risk fresh wood with a Panaque. Plus, due to similar experiments with leaves, I think the microbial community of early wood decomposition, which may depend more on species-specific traits of the wood in question, would differ from the microbial community of late wood decomposition, which would probably be more general. I wouldn't be surprised if the fish's themselves preferred the degraded wood because of its more general nature but also because it doesn't have the tannins that may deter feeding.

As a last note, German finds that these fish primarily feed on disaccharides that the microbes release, at least as a carbon source. Although I don't think he notes what type of disaccharides, many disaccharides are easy to buy. Fructose can be gained from fruits, and sucrose is table sugar. Obviously we can't just dump table sugar in the aquarium, but fruits are a possibility. Perhaps providing loricariids with disaccharides will help contribute to their diets more than providing wood, skipping the step of developing a microbial community on the wood in your aquaria.

[DP German]

Nice synopsis, Milton! I didn't mean to give the perception that they ONLY feed on "soft" wood, because, as Nathan's data suggests, they certainly do some hard core reasping on harder substrates as well (especially Panaque cf. nigrolineatus "Marañon" and others in the P. nigro clade). But, if the fish are able to survive on wood alone it would be softer woods that would allow for this, and yet, this has not been observed. The disaccharides they do well with are beta-glucosides (originating from cellulose and laminarin degradation) beta-mannosides (from mannose degradation) chitobiose (from chitin degradation), and alpha-glucosides (from starch degradation). They don't have the enzymes for beta-xylosides (from xylan degradation), and this makes sense because vertebrates don't have the biochemical pathways to utilize xylose, the monomer produced in beta-xyloside digestion. But, I think your observation is correct, a little fruit or carrots couldn't hurt. My Pterygoplichthys and Panaque love Wardley algae discs.

I exchanged a few e-mails with an aquarist in Germany who pointed out that fry of some ancistrines simply don't do well without wood in their tanks. I am sure that others have noticed that loricariids don't always do well with commercial fish feed as their only food source. Some of this may have to do with intake (not to mention, wood provides habitat: Wright JP, Flecker AS (2004) Deforesting the riverscape: the effects of wood on fish diversity in a Venezuelan piedmont stream. Biological Conservation 120:439-447).

Loricariids are geared for high levels of intake of low-quality food, and thus, have rapid gut transit. Consequently, the fish have high activity levels of digestive enzymes that degrade proteins, lipids, and soluble carbohydrates in the diet—all of the stuff that is easy to digest quickly. When fish consume richer foods—commercial fish food is certainly richer in protein, lipid, and soluble carbohydrates (e.g., corn starch) than a wild diet of detritus—the fish will have lower overall intake and slower gut transit. Because of the high protease (protein degrading enzymes) lipase (lipid degrading enzymes), and amylase (starch degrading enzyme) activities in the loricariid gut, this will result in more complete digestion of lipids and soluble carbohydrates from the commercial fish feed. All of that extra energy is going to be stored as fat, and fishes can store a considerable amount of fat in their livers. This isn't good over time. Liver problems lead to a cascade of other physiological problems down the road. In captivity, wood, as Janne mentioned, may be a source of fiber to keep things moving through the gut and prevent the over assimilation of all of that extra energy that they normally don't encounter in nature.

By fiber here I am referring to cellulose and hemicellulose. Lignin is a different beast altogether and I stand by my assertion that adding lignin to fish feed is nothing other than filler to add bulk so that the fish food company can make more money.

Cheers,

Donovan

[Suckermouth]

I certainly didn't mean it to be a synopsis, but thanks.

It's good to know that wood specialists will chew on harder woods than non-specialists, and is more like what I'd expect given their specializations to do so. On the other hand, in wood that has not been degraded much, we can't expect much in the way of a microbial community and material for them, but they could still serve a function of fiber or "roughage" coupled with a relatively rich algae wafer diet.

It's also a good point that you brought up about richness of foods. Although we'd like to give as much nutrition to our fish as possible, detrivores such as loricariids are adapted to eat tons of low-quality food. So it looks like maximizing disaccharides like I was thinking above, without providing roughage, wouldn't be good. Although roughage is wood in the case of the wood-eaters, other detrivores and generalists likely don't consume as much wood. So I wonder whether generalist loricariids are more adapted to a richer diet and/or are they adapted to using another form of low-nutrient matter to clear their system, perhaps sand as you found in P. disjunctivus. Sand/sediment has also been found in the stomachs of other loricariids, such as Ancistrus and Hypancistrus. Also, you note that while P. disjunctivus would consume wood in captivity, you didn't find any wood in wild fish, which leads me to believe that generalists, while able to use degraded wood, do not use it if they have the choice. Therefore, if the focus of providing roughage was the goal of an aquarist, I wonder if providing some sand/silt would be more beneficial, considering the sand doesn't have the problem of needing to be chewed off, like pieces of hard wood.

One of the interesting issues of aquarium care of Panaque is that Panaque are rather slow-growing. I have a specimen myself (in my avatar) that I have kept for over eight years now, and in that time it has grown very little, maybe a few inches. Growth of about 1 inch per year seems to be what people claim, although my Panaque is even slower than that. Unfortunately, no one has done a study where they looked at Panaque otoliths to estimate growth rate in nature, so I don't know if they are also slow-growing in nature. I had thought that aquarists were somehow missing something key in their diet, but now that it's been shown that their digestive tract is not extremely specialized, I'm not so sure.

[racoll]

It is my educated guess that while the majority of nutrition in captive raised loricariids (wood and aufwuchs/detritus feeders) should come from prepared foods, having wood in the tank is a good safety net.

Wood provides the roughage to maintain transit through the gut. I also suspect, as mentioned above, that feeding say a Panaque nothing other than fishmeal-based protein rich foods would be detrimental long term.

What really should be developed is a pleco wafer that has say one tenth of the protein/fat content of regular wafers, with a high cellulose content. This product could be fed generously, for constant grazing, without fear of polluting the water.

[DP German]

I agree about the composition of the food, but generous feeding of any type will cause fowling in a relatively short period of time (1-2 weeks). One thing I noticed in my experimental tanks is man, loricariids shit a ton, even when eating algae discs!

[Janne]

I exchanged a few e-mails with an aquarist in Germany who pointed out that fry of some ancistrines simply don't do well without wood in their tanks.

I have made several experiment growing small Panaque species offspring's with and without access to wood, fry with wood in their tank grows much better the first 3 months compared to fry without access to wood... both is fed the same amount of a comercial food and the only different is that one group have a small piece of wood in their tank and the other not. I don't think they use any nutritions from the wood.

In captivity, wood, as Janne mentioned, may be a source of fiber to keep things moving through the gut and prevent the over assimilation of all of that extra energy that they normally don't encounter in nature.

Species caught of scientist's is mostly caught under the dry season, do Loricariid's eat the same kind of food every day all year around? I don't think so. I think they could consume "wood" even in nature, not always necessary as a source of food.

So I wonder whether generalist loricariids are more adapted to a richer diet and/or are they adapted to using another form of low-nutrient matter to clear their system, perhaps sand as you found in P. disjunctivus. Sand/sediment has also been found in the stomachs of other loricariids, such as Ancistrus and Hypancistrus.

Fishes living in water's with extremely low conductivity which is the same that no calcium or almost none other minerals at all is available except from the source of food, many species that not are carnivores must find a secure source for minerals. Both fishes and other animals have been seen to eat mud in the nature, could that be an explanation why they found sand in some speciemen?

One of the interesting issues of aquarium care of Panaque is that Panaque are rather slow-growing. I have a specimen myself (in my avatar) that I have kept for over eight years now, and in that time it has grown very little, maybe a few inches.

If buying a Panaque species from the nigrolineatus complex at 10 cm it can reach 20 cm within 1-1,5 year and 30 cm within 3 years, they are not growing slower then other larger species. There are many myths about slow growing fishes, the different is the environtment we provide and the fish keeper. But of course there can be induvidual differencies caused of other reasons for slower growth, for example if you buy 2 at 10 cm... the strongest of these 2 will grow much faster then the other.

What really should be developed is a pl*co wafer that has say one tenth of the protein/fat content of regular wafers, with a high cellulose content. This product could be fed generously, for constant grazing, without fear of polluting the water.

There are already wafers on the market containing "Cellulose", plecos don't like it. Better to let them eat other foods with low protein as often they want and like DP German said, clean the tank often because they shit a lot under good conditions

Janne

[Suckermouth]

As far as sand consumption goes, I think that's a byproduct of feeding on foods that are on/in the sand, such as invertebrates; analogously, the indigestible pieces of wood in the Panaque gut contents is a byproduct of feeding on the disaccharides and detritus that are on the wood. Rhinelepis has been shown to feed by sucking up sand and sifting it through their gift rakers.

Janne, what kinds of conditions do you think help promote Panaque growth? That's interesting that you say slow growth is a myth. My own sample size of one Panaque certainly isn't exactly good evidence to support that they're slow growing.

And about plecos pooping a ton? So true. As long as you're giving them food, they're pooping it right back out...

[DP German]

AS far as the sand thing goes... I do think its consumption is incidental. Pterygoplichthys in FL live in sandy, spring-fed rivers and feed on periphyton and other items (like inverts) from the surface of rocks and the river bed. They can't help but ingest sand as they ingest algae or worms from the river bed. Not sure about including sand in a tank for loris. They don't hold onto the sand and use it as a grinding surface like mullets and some surgeonfish do. But, it would certainly pass through the gut quickly!

I am glad that other people are putting it together that loricariids have rapid gut transit and crap a lot. When I presented my work at one conference (not all conferences; most of the time people seemed to agree) one researcher thought that their long gut meant that they held on to the food for a long time. Not the case.

I am so glad that this dialogue picked up again. I am enjoying these exchanges!

Cheers,
Donovan

[Shane]

what kinds of conditions do you think help promote Panaque growth?

There have been some studies that show water quality to be more important than food availability w/ re to growth. I am at work so do not have a citation at hand, but the experiment is easy to replicate. Use two 10 gallon tanks, place 10 fry in one and 10 fry in the other. Give one tank a measured amount of food and low frequency water changes (say 10% weekly). Give the other tank 1/2 as much measured food and a good water change regime (say 20% daily). The fry in the tank with less food and more water changes will exhibit faster growth.

I would love it if someone would duplicate this experiment with say Ancistrus fry for a Shane's World article.

AS far as the sand thing goes... I do think its consumption is incidental.

Once again I think this may be both by sp and specific environment. Sand consumption makes a lot of sense from a nutrional stand point in very mineral poor waters like those originating in the Guyana Shield. This should be an easy one to test for actually.

-Shane