New information about gravel...

[Petersgirl]

Hello fellow axxie lovers!

I was trawling Wikipedia and, despite my awareness of the caution one must take while exploring its briny depths, I came across a kraken of the most extraordinary kind.

Now, call me overly simplistic here, but I got the impression that the general consensus among owners on Caudata was that gravel isn't a good choice for substrate where axxies are concerned.

The Wikipedia article seems to think otherwise, however:

'There are persistent statements in pet care literature that axolotls cannot be kept on gravel because gravel causes fatal digestive impaction. There is no evidence to support this myth and counter evidence that normal healthy axolotls regularly ingest gravel and pass it without any negative consequences. The axolotl, like many amphibians, may be deliberately ingesting gravel to act as a gastrolith providing buoyancy control and aiding digestion, preventing impaction, rather than causing it. Axolotls deprived of appropriately sized gravel will ingest anything else they can find while attempting to satisfy their instinctive need for gastroliths and this behaviour, combined with lack of appropriate gastroliths, may be a cause, among others, of fatal impaction.'

Sources are given and the article can be accessed at https://en.wikipedia.org/wiki/Axolotl.

What do we think? Personally, I'm staying firmly no-gravel for my own tanks (bare bottom or sand are the two I most like), but this does give me food for thought.

P.S I am aware Wikipedia is often cited as an unreliable source, but that aside, people will be reading this for information and I'd like to know what you all think.

 

[Mark]

The author provides no evidence that axolotls ingest gastroliths. They reference a paper which suggests frog tadpoles ingest substrate particles for buoyancy and another study which shows that x-rayed axolotls kept on gravel often ingest it. The presumption that they do it on purpose is not backed up with any evidence as far as I can see.

I find it hard to believe that an aquatic animal which has evolved to catch prey by “inhaling" it into their mouths wouldn’t have a degree of substrate in their digestive system at all times. An axolotl kept on a gravel substrate will therefore undoubtedly ingest gravel but whether it’s accidental or on purpose would need some experimentation. It wouldn’t be difficult to prove but you’d need access to an x-ray machine.

 

[JM29]

Hi,

This Wikipedia article cites some sources which deserve further reading.
One of them (Wings, 2007) proposes a definition for gastroliths :
"a hard object of no caloric value (e.g., a stone, natural or
pathological concretion) which is, or was, retained in the di−
gestive tract of an animal."
This definition is very large and includes every hard object which can be found in the digestive tract, no matter if it has a function.

In the same article, cases of gastroliths in Taricha are cited but the author admits the ingestion was incidental.

Finally, the notion of gravel should be precised in terms of grain diameter versus animal size.

 

[Skudo09]

This has come up a couple of times. Wikipedia is a not the most reliable source of information and although there is sometimes useful information I would take information on there with a huge grain of salt and research from many other sources.

I would think to really determine this we should look at what substrate was natural to their wild native habitat. I doubt that they have much in the way of gravel, particularly the type often used in aquariums. I would assume much of the substrate was more silt than anything. I am sure they would occasionally consume some substrate given their vacuum like eating habits. Given the amount of impaction cases seen here from gravel, I am certainly not risking it any time soon... Although I have read many times that many keepers successfully keep axolotls on small 1-2mm smooth rounded gravel (no jagged or sharp edges) but for the most part it is just easier to advise keepers to get sand or bare bottom to be safe and save confusion on what is safe...

 

[AxolotlChris]

Yes this has been covered a few times, these two threads should cover it:
http://www.caudata.org/forum/f46-beginner-newt-salamander-axolotl-help-topics/f48-axolotls-ambystoma-mexicanum/f57-axolotl-general-discussion/104516-axolotls-gravel-gastrolith-buoyancy-aid-not.html
http://www.caudata.org/forum/f46-beginner-newt-salamander-axolotl-help-topics/f48-axolotls-ambystoma-mexicanum/f57-axolotl-general-discussion/102514-gravel-substrate.html

Its highly unlikely that Axolotls use gravel as gastroliths or for buoyancy, there is virtually no evidence. And if Axolotls are kept on gravel (which is very common with experienced keepers) it will be smooth and rounded between 1-3mm in size so not to cause internal issues.