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Are woodeaters herbivore ?

Wood is plant matter, so by strict definition of the term “herbivore”, the answer is yes.

That's one of those questions that is much easier to ask than to answer...

To the best of my understanding, based on the various research articles on the subject, wood eaters get their nutrition from little microorganisms (bacteria, fungi and small insect[-larvae]) that live in the wood, but also the waste products/byproducts of these microorganisms.

In an aquarium, they will indeed, eat vegetable matter if available.

Does this make them vegetarian? I'm not sure...

But as Silurus says, the wood itself is plant matter, so that part is definitely "herbivore". But I'm not convinced that this is what you are actually asking, hence the explanation above.

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Mats

I hate to sound like a pedant today, but all herbivores essentially obtain the bulk of their nutrition through microorganisms anyway, since vertebrate digestive systems are intrinsically unable to process cellulose (which makes up the bulk of plant matter).

This is why ruminants (e.g. cows) have a four-compartment stomach. The first two compartments function as fermenting vats that allow microorganisms to break down the cellulose.

If we consider ruminants to be herbivores, we can consider wood-eating fish to be herbivores.

And the point I'm trying to make is that the microorganisms are not part of the digestive system INSIDE the fish.

I'm not disagreeing they are herbivores, just that they have a more complex relationship with the microorganisms than some of the more "direct" herbivores.

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Mats

whats a wood eater?

several popular catfish in the hobby actually eat wood.

the best known is Panaque and its smaller cousins (which are also panaque, but often sold as Peckoltia) like the Clown pleco

these fish literally eat wood; in the wild they munch on sunken trees and branches that have fallen in the rivers.
also when the rain season comes a very large part of the forest floods.....many fishes from the amazon can be viewed as 'forest dwellers", because for half a year they do literally that; swim the forest!

so you can tell someone that there's a forest where the fish live.

the many fish that dwell the flooded forests have adapted to every available food source.
some have taken to hunting insects sitting on the branches above the water; most famous of these is the Arowana

some feed on the leaves and falling fruit from the trees; many large catfish do so and the huge wheel-sized characins called Pacu's.

then there are those that hunt and kill birds (!), especially young birds that fall from nests; Piranha's feed on heron chicks for example.

and with all the available wood just standing, laying and floating around a wood-eating fish was bound to happen; Panaque's do this.

they also go through bogwood and backpanels like a beltsander when kept in a fish tank.
a healthy large Panaque can do a lot of damage in there....

for an overview of the Panaque catfish, see here:
http://www.planetcatfish.com/catelog/ge ... enus_id=27

There are also a lot of plecos that scrape wood as a partial "supplemental diet". Almost all of the medium to large herbivore plecos will happily "clean" wood, and you can see that they it is passing through the fish, as the poo comes out black or dark brown.

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Mats

a fine example of a "semi woodeater" that's common in the hobby is Sturisoma spp.

Sturi's in a tank with used bogwood always poop in exactly the same color as said bogwood and in time the softer pieces are cleared up.

Hypostomus -another plec that's not a true wood eater- has the same behavior.

Hi all,
They are technically "xylophagous" (just means wood-eating) <http://en.wikipedia.org/wiki/Xylophagy>, a couple of years ago Donovan German published the work that Mats is referring to, and we had a discussion on this forum.

German, D. P. (2009). "Inside the guts of wood-eating catfishes: can they digest wood?" . Journal of Comparative Physiology B 179 (8): 1011.
<http://www.springerlink.com/content/30179842g1315q6h/>

To "cut to the chase" Dr German found that although Panaque species had a specialised dentition to rasp wood, they didn't have a specialised gut microflora, or gut structure, to allow them to digest the lignin and cellulose in the wood. In this they differ from true "xylophagous organisms" like Termites, Bark Beetle larvae or Beavers which have these adaptations. His research suggested that they gained their carbon from the organisms in the partially degraded wood.

The "Basidiomycota", the group of fungi that includes the mushrooms we eat, are some of the few organisms that can degrade lignin and their hyphae are probably a major source of food for these fish.

cheers Darrel

I remember when I had my royal. In the tank he was in i scaled with a couple nice pieces of harder wood (wormwood I believe the pet store called it) and two pieces of softer wood that were attached to slate. In the 4 years I had him (I unfortunately gassed him with co2 ) he completely ate both the softer pieces that were in slate and made some really noticeable rasp marks in the harder wood.

In my L183 starlight breeding tank I have quite a bit of what I would call medium hardness wood and over the the past roughly 3 years they have eaten approx half the wood in the tank. The water that is siphoned out from the gravel with a gravel vacuum smells absolutely horrible, almost like fermenting wood. It also looks just like tiny little pieces of wood so I can pretty safetly say that in their stomachs not much is happening.

Hi all,

The water that is siphoned out from the gravel with a gravel vacuum smells absolutely horrible, almost like fermenting wood. It also looks just like tiny little pieces of wood so I can pretty safely say that in their stomachs not much is happening.

Yes that is pretty well what Donovan found, and it is why Panaque spp and other wood eaters, some Ancistrus spp., Cochliodon group Hypostomus spp. etc. produce so much faeces and wood shavings. They have to process a huge amount of wood to get enough food.

Donovan thought that Giant Panda was a good analogy, where it had a morphological adaptation to eat Bamboo (False thumb), but didn't have the genetic potential to modify its gut, and still had a carnivores gut. The end result was that Panda's had to eat all day & night, and continually cr*pped from the other end.

cheers Darrel