About
Axolotls...
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Metamorphosis and the Mexican Axolotl
What Changes Occur During Metamorphosis?
Housing The Metamorphosed Axolotl
Temperature
Lighting
Ventilation
Water Filtration
Food
Handling
Mixing Species
References
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- The Mexican axolotl, Ambystoma mexicanum is neotenic: It
retains important larval features, most notably its gills and tailfin,
and its aquatic habit throughout its life. Axolotls cannot be forced
to metamorphose by gradually lowering the depth of the water they are
housed in, nor will the addition of iodine initiate transformation.
Metamorphosis can be forced, however, with thyroxine, a hormone produced
by the thyroid gland (refs).
Spontaneous metamorphosis in this species is rare, but it does occur.
In some cases spontaneous metamorphosis may be caused by diet. For
instance, some years ago, the Axolotl Colony switched from feeding
our axolotls beef liver (primarily) to a fishmeal-based pellet. Subsequently,
the rate of spontaneous metamorphosis in the colony increased dramatically,
and it is still higher than it was previous to the dietary change,
although we do not breed the axolotls after they metamorphose. Since
most of our axolotls do not metamorphose even though they are all
on the same diet, the sensitivity to thyroxine must vary from axolotl
to axolotl even within our highly inbred colony.
In our experience, axolotls that have metamorphosed are more difficult
to house and feed, and they seem to have less resistance to disease.
We have never bred metamorphosed animals.
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- Axolotls that are transforming to the terrestrial form resorb their
gills and tailfin, and their eyes bulge out and develop lids. They abandon
the habit of gulping air and begin to breathe through their nostrils.
The color pattern may become more vivid and defined, and the skin becomes
tougher and able to withstand drier conditions. Metamorphosing and metamorphosed
axolotls also molt, shedding their skin in thin, black, translucent
sheets. The complete transformation process takes a number of weeks.
It may be several months before the last nubs of the gills are gone.
Usually while metamorphosis is going on, the axolotl will stop eating
or will eat very little.
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- Curator's Opinion: After many unsuccessful experiences housing
terrestrial axolotls in various soil and water environments, I
started asking those researchers who have housed terrestrial axolotls
successfully how they did it. It sounds like the most successful
system is leaving the axolotl in its tank and buiding a climbing
place which peaks out of the water. If the tank isn't covered,
it would of course need to peak in the middle of the tank so that
the axolotl doesn't crawl out! Axolotls get too dry in soil environments.
They don't bother to go to the water and soon get too stiff to
move. I think that they aren't really very good at metamorphosing
and possibly don't get the water retention part right during the
change. In a bowl or tank where the water is deep and they have
a place to climb, they crawl up just enough to stick their noses
out and leave the rest of their bodies in the water.
- What the literature says: When the axolotl is mostly done transforming, set up a simple vivarium.
Put soft, loose dirt 10-15 cm (4-6 inches) deep in an empty fish tank
or similar container. Dry potting soil or peat works well. At one end,
place a shallow container at least 20 cm in diameter (8 in) and about
8-10 cm (3-4 in) deep. Fill the container with water. Place a few objects
in the tank as hiding places. Change the water in the container regularly.
The dirt will only need replacing occasionally.
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- Keep the temperature in the vivarium cool, no more than 22°C
(72°F). If there is some variation in temperature of different
parts of the tank, the axolotl will be able to choose the temperature
it prefers.
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- Do not place a bright or hot light over the vivarium or place it in
direct sun. Lighting should be indirect and subdued.
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- Use a screen cover or other cover that allows air circulation, but
do not create drafts.
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- If you set up your tank so that the water cannot be conveniently changed,
use an appropriate filtration system to keep the water clean.
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- Worms, crickets and other insects, and commercial pellets are suitable
for terrestrial axolotls. Many transformed axolotls continue to prefer
to feed in the water. Finding a food they will accept is the most important
thing. Feed daily if the axolotl is willing to eat that often.
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- Do not handle the axolotl more than necessary. If you need to handle
an axolotl, be sure your hands are clean and free of soap residues.
Scoop up and cage the axolotl in your two hands without squeezing it.
Use gloves or a net if you prefer. Be sure to wash your hands thoroughly
when you are done handling the axolotl, since amphibians can carry Salmonella
and other diseases.
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- A note on keeping different species together in one tank: many species
cannot tolerate the toxins produced by other species. Putting them together
may result in the deaths of one or more species. Disease transmission
is also more likely when different species are housed together. The
Axolotl Colony has been successful, however, in housing terrestrial
axolotls and tiger salamanders of similar size together.
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References
- Salamanders and Newts: A Complete Introduction, by Byron
Bjorn (1988). NJ: TFH Publications.
- The Completely Illustrated Atlas of Reptiles and Amphibians,
Fritz Jurgen Obst, et. al. (1988). NJ: TFH Publications.
- Salamanders
and newts, by Melissa Kaplan, (1993).
- Keeping and Breeding Amphibians, by Chris Mattison (1992).
NY: Sterling Publishing Inc.
- Breeding Terrarium Animals, by Elke Zimmermann. NJ: TFH
Publications.
- Encyclopedia of Reptiles and Amphibians, by John Breen.
NJ: TFH Publications.
- Axolotls, by Peter Scott. NJ: TFH Publications.
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URL: http://www.indiana.edu/~axolotl/axolotls/shortguide/terrestrial.html
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