As many of you know, I have been away for the past few weeks due to health issues (unrelated to the current virus crisis). First, I’d like to thank you for your patience, concern and well-wishes. I’m doing much better!
The government of Quebec has recently announced the closure of all non-essential services. Thankfully, pet stores are considered essential, so I will be returning to work on March 31st as planned. For the foreseeable future, I will not be holding regular store hours, but will be conducting business online or by appointment. You may contact me via email, Facebook, or call/text 514-882-2758.
Important note regarding shipping of live animals: Due to the current self-quarantine measures adopted throughout the country, there has been a major increase in online purchases of all kinds, causing extreme delays for all regular shipping providers. For the time being, all live animal shipments will be conducted through Reptile Express, a specialized shipping service which guarantees delivery times and live arrival. Since my shopping cart application is not equipped to live estimate this company’s shipping rates, you will need to contact me to obtain a personalized quote. Thank you for your understanding!
Tip #1: Most axolotls will have grown out of their cannibal phase by the time they reach a full body size of 3.5 to 4 inches. Make sure to pair axolotls which are similar in size. Cannibal phase or not, if one’s head can fit inside the other’s, it will be considered food!
Tip #2: Choose a time when both axolotls seem relaxed, healthy and have a full belly. It’s very important to feed them well beforehand!
Tip #3: A protein-deficient axolotl is likely to bite tankmates, regardless of age, relative size and other circumstances. So make sure you’re feeding an appropriate diet, and if your axolotl is a rescue, give them a couple weeks of adequate nutrition before introducing them to your other lotls.
Tip #4: Supervise the first interaction and get ready to separate if needed. Getting in each other’s space is okay. Sniffing each other is okay. Being a little jumpy is normal too. Fast stomping towards the other with the nose down to the ground is a bite waiting to happen, so get ready to intervene. Snapping right in front of each other’s face is more of a threat, but still a sign that the axolotl isn’t ready to accept a tankmate. Separate and try again in a few weeks.
Tip #5: If all goes well for the first few minutes, supervise at feeding time for the first several days. That’s usually when aggressive behavior comes out. Try to feed in separate areas of the tank so that they aren’t tempted to go for each other’s food. Stealing food from each other’s mouths is a no-no, as it encourages bites on both sides. Snapping close to each other’s limbs is also not good, so try not to let the food end up close to someone’s toes. Feed the more food-aggressive axolotls first, then feed the more timid ones at a safe distance from the more voracious ones.
Tip #6: If you notice that one axolotl tends to hide a lot, won’t come out at feeding time, and turns away from food, they are either feeling sick or are scared of a food-aggressive tankmate. Separate and try again once both animals seem happy and healthy.
Tip #7: If a pair doesn’t get along right away, don’t get discouraged. Separate them and try again in a few weeks. Just because it didn’t go well last time doesn’t mean it won’t work out next time. Axolotls live in the moment, they don’t hold grudges. I promise!
In part 2 of this article, we went over albinism, a recessive genetic mutation which affects one type of pigment cells (melanophores, responsible for the dark pigment eumelanin). As you can easily guess, there are also mutations which affect the other two types of pigment cells: iridophores, which produce shiny white crystallized purines, and xanthophores, which produce yellow pteridines. In this section, we will focus on these two mutations, which are a bit more complex than albinism.
Melanism is a recessive mutation similar to albinism, but instead of affecting melanophores, the mutation acts on iridophores. All axolotls receive either the M or m allele from each parent, which means their genotype for the melanism trait is either:
M/M (homozygous dominant)
m/m (homozygous recessive)
Homozygous dominant and heterozygous axolotls develop normal iridophores, which means they are able to produce crystallized purines (the shiny white pigment). Homozygous recessive axolotls are called melanoids. Since they have no iridophores, they are unable to produce cystallized purines.
This mutation also has a spillover effect: the lack of iridophores triggers the conversion of some xanthophores into melanophores. This is why melanoid axolotls show more eumelanin (black) than any other color morph, and almost no pteridines (yellow). This gives them a grey appearance, which can border on blueish under the right wavelengths.
Due to the reduced number of pteridines, which are important to immune function, melanoid axolotl larvae have a slightly lower survival rate than wild-type or albino axolotls. This is why melanoid axolotls they tend to be a bit more expensive and slightly less common on the market than other color morphs.
As you can imagine, axanthicism acts on xanthophores, the pigment cells responsible for producing pteridines. But the name of the trait, which means “lack of xanthophores”, is actually misleading. As it turns out, axanthic axolotls do have a certain amount of xanthophores, but those xanthophores are unable to produce pteridines due to a genetic mutation, which is believed to have originated from a virus.
Even though they can’t produce pteridines, the mutant xanthophores are able to store some yellow pigments from the axolotl’s diet (chiefly riboflavin, also known as vitamin B2). This helps compensate a bit for the lack of pteridines, but since they are slowly accumulated over time, axanthic larvae still have a low survival rate compared to other color morphs. This, along with the strict import laws currently in place, explains why axanthic axolotls are nearly impossible to find on the Canadian market.
In addition to causing a complete lack of pteridines, the axanthic mutation prevents iridophores from differenciating during development. As a result, axanthic axolotls often look a lot like melanoids. One way to tell them apart is to look at them under a blueish light. The complete absence of yellow pigments at birth tends to give axanthic a purple hue, whereas melanoids are more of a blueish grey. The purple effect tends to fade over time due to the accumulation of other yellow pigments, but some axolotls (such as Sarah, below) do manage to retain it through adulthood.
To make matters more confusing, axolotls can be both axanthic and melanoid. If an axanthic axolotl is especially dark, chances are it is also melanoid, but there is no way to be certain unless the genotype of both parents is known. If an axanthic axolotl accumulates a lot of yellow pigment over the years, then it probably isn’t a melanoid, as melanism further reduces the overall number of xanthophores.
There are six known genetic traits that affect an axolotl’s pigmentation:
The Copper trait
The GFP trait
All six of these traits follow a Mendelian pattern of inheritance, which is good news, because it’s a very simple pattern to explain and understand. Trust me! Keep reading and you’ll be an expert on the topic in less than 5 minutes.
Mendelian inheritance: the Ikea metaphor
DNA is a pretty amazing thing: the complete set of instructions for the construction of one particular living organism. It’s often portrayed as one huge chain, but DNA is actually broken into individual segments called chromosomes. Think of each chromosome as one assembly instruction booklet, like the ones that come with Ikea furniture. Obviously it takes a lot of instructions to build a whole living being, so we need a whole pile of booklets.
The instructions inside the booklets also have to be fool-proof, because the ones reading them and performing the assembly are proteins, which pretty much work like mindless drones. This is fine, except that when the information in one booklet is messed up or missing, the proteins can’t pick up the phone and call Ikea for help.
Luckily, each instruction booklet comes in two copies: one that was obtained from the animal’s mother, and one from its father. So even if there is missing information in one of the booklets, the protein-drone just needs to look at the other copy. With any luck, the correct information will be there.
This is the basic principle behind Mendelian inheritance.
Let’s say I want to build a chair and I have two instruction booklets in my possession. Version 1 (which I got from my mom) shows detailed, step-by-step assembly instructions. Version 2 (which I got from my dad) has a bunch of mistakes in it, and it’s very confusing. If I follow version 1, I’ll end up with a chair. If I follow version 2, I might end up with some weird contemporary art sculpture that may or may not crumble when I sit on it. Obviously, I would rather follow version 1, right? I might call my dad up afterwards and tell him “Hey Dad, just so you know, the instructions you gave me made no sense! It’s okay though, I used a different set of instructions and I managed to build the chair in the end.”
But what if both of my parents had given me the faulty version 2? Since I’m not a mindless drone, chances are I would have gone “uhh, I don’t think this is right.” But if I were a mindless drone, I probably would take the fact that both sets of instructions are saying the same thing as a sign that the information is correct, and I would have built the weird contemporary art sculpture. And who knows, maybe the sculpture would have turned out even better than some boring old chair!
When I say that a particular genetic trait follows a pattern of Mendelian inheritance, what I mean is that the assembly instructions for that particular trait come in two different versions, and given the opportunity, the assembly protein-drone will always prefer one version over the other. The version that is always preferred is called the dominantallele. The one that’s used only if no other instructions are available is called the recessive allele.
Mendelian inheritance: the albinism trait
If a chromosome is like an instruction booklet, the section of the booklet that contains instructions for one particular trait is called a gene. Just like the booklet in our previous example, the albino gene comes in two versions: allele A and allele a. Dominant alleles are always represented by capital letters, whereas recessive alleles are always lowercase.
Just like humans, axolotls receive two versions of each chromosome — one from their mother and one from their father. Every axolotl either ends up with one of these pairs:
A/A (two identical copies of the dominant allele)
A/a (one copy of each allele)
a/a (two identical copies of the recessive allele)
Axolotls who end up with two copies of the dominant allele are said to be homozygous dominant. The ones with two copies of the recessive allele are called homozygous recessive. If they have one copy of each, we call them heterozygous (from homo = same, and hetero = different).
So what makes allele A the dominant version of the gene? It contains a set of instructions for the construction of melanophores, the pigment cells that produce the dark pigment eumelanin. In allele a, those instructions are either erroneous or missing due to a genetic mutation that randomly occured at some point during the evolution of the species. We call this mutation albinism.
Albinism works in a fairly straightforward manner: when an axolotl is homoyzgous for the recessive (mutant) allele a, it is unable to produce eumelanin (the brown/black pigment) because it simply does not have any melanophores. All other axolotls have melanophores and are able to produce eumelanin (with the possible exception of copper axolotls, which we will discuss later).
Even though albinism is a recessive mutation, it doesn’t mean that allele a is worse than allele A, or that albino axolotls are inferior in any way. Some mutations can yield positive results! Look at how cute these albino axolotls are:
Of the six mendelian traits that affect pigmentation, albinism is the most straightforward, because it only acts on one type of pigment cell. The other traits are slightly more complex, but the principle behind them is the same: as long the right sets of instructions are present, all pigment cells will be created and behave normally. But if they’re not, the assembly drones will follow whatever instructions they can find, and turn those functional chairs into pieces of art!
An axolotl’s coloring is the result of genetics, and to a lesser degree, environment and diet. Let’s go over the different color pigments involved, and you’ll understand what I mean.
The three natural color pigments are:
Eumelanin (brown, black)
Crystalized purines (iridescent white)
Pteridines (yellow, orange)
There is also a fourth pigment that is present in some transgenic axolotls:
Green fluorescent proteins (bright yellow, glowing neon green under a UV light)
We’ll get back to this one later — let’s focus on the three natural pigments first. These are naturally present in the majority of axolotls. Besides looking pretty and helping with camouflage, they also come with health benefits: eumelanin helps protect the skin against UV radiation, and pteridines play an important role in the axolotl’s immune system.
You can see all three pigments expressed in the picture below:
Axolotls that possess all three pigments are called wild-type. Even though they all have the same pigments, there can be a lot of variation in wild-type appearance. For instance, the axolotls shown above have a lot of yellow pteridines, which gives them an overall olive tint. They also have white spots on their tails. If I had taken the photo with the flash on, you would have seen that those white spots are shimmery, because they are made of crystallized purines.
The axolotl in the photo below is a much darker wild-type:
In this photo, we can see a lot of eumelanin. The other pigments are also present, but not very noticeable. You can see a little bit of crystallized purines in the eye ring and the tip of the gill stalks. Pteridines are almost completely invisible under the dark eumelanin.
Let me show you one more, very different wild-type look:
Isn’t this boy gorgeous? Here, eumelanin forms the base skin color, but the pteridines and crystallized purines being layered on top of each other create a gold flake effect.
In addition to the variety among wild-types, there are a lot of different color types, or “morphs”, besides wild-type. Over the course of their history, axolotls have undergone several genetic mutations which affect their pigmentation — some of which are natural, some of which are the result of human intervention.
Here are the six main genetic traits that affect axolotl pigmentation:
Albinism (affects eumelanin)
Melanism (affects crystallized purines)
Axanthicism (affects pteridines and crystallized purines)
Leucism (affects eumelanin, pteridines and crystallized purines)
We’ll talk more about these traits in the next section of the article. For, now I just want you to keep in mind that there are several genetic traits that can essentially switch pigment production on and off, or affect how pigments are distributed around the body.
Let’s take a closer look at what each pigment looks like individually.
Eumelanin is the pigment responible for shades of brown and black. It is produced by pigment cells called melanophores. To give you a better idea of what the pigment looks like on its own, here is what an axolotl looks like when it shows only eumelanin:
Fun fact: the amount of eumelanin produced by an axolotl depends on two things: genetics, and environment. Axolotls whose parents were especially dark tend to exhibit similarly dark features. Axolotls who grow up in dark environments also tend to exhibit darker features than ones kept in lighter environments.
The absence of eumelanin, due to an inability to produce melanophores, is called albinism. Here is what an axolotl looks like when you completely remove eumelanin, keeping only the other two pigments:
Pretty neat, right?
Crystallized purines are iridescent white pigments, which means they shimmer in a sort of rainbow effect. Combined with pteridines, they can also create a shiny golden color, as we’ve seen above. Crystallized purines are produced by pigment cells called iridophores. Here is what iridophores look like on their own:
The inability to produce iridophores is called melanism. Notice how the shiny white pigments are missing in the picture below:
Melanism is a little bit more complex than albinism. We’ll talk about it more in part 3 of this article.
Pteridines are responsible for yellow and orange coloration. They are produced by pigment cells called xantophores. This is what pteridines look like when you remove the other two pigments:
The inability to produce pteridines is called axanthicism. Axanthic axolotls are exceedingly rare, if not impossible to find in the Canadian pet trade. This is partly due to strict import laws, and partly due to the effect axanthicism has on axolotl health. Since pteridines play a role in immune function, axanthic axolotls have a lower survival rate than other axolotls.
In the absence of pteridines, axanthic axolotls take on a purple-grey look:
Do you notice some odd things about this picture? Axanthicism is a much more complex mutation than albinism and melanism. We’ll talk more about it when we get to the next section.
Green fluorescent proteins (GFP)
In the course of their use as animal research models [more on this soon!], some axolotls got a pretty cool addition to their genomes: the GFP trait. Originally found in a species of jellyfish, this trait causes nearly every cell in the axolotl’s body to produce a bright yellow protein which glows neon green under a UV light. Why is this cool? First, it’s been very helpful to researchers working on limb regeneration and organ transplants. Second, it looks very pretty! And third, the trait can be passed down from generation to generation. But my favorite thing about it is that, since the effect isn’t limited to pigment cells, it isn’t affected by leucism. You’ll see what I mean when we get to the next part!
Now that you have a good idea of what the individual pigments do, let’s take a look at the genetics behind them!
It’s not uncommon for axolotls to refuse food for a few days when they first arrive in a new home. Keep in mind, s/he is trying to adjust to a whole new environment, including a new owner, and possibly different food and feeding methods. Be patient! S/he will warm up to you once s/he realizes that there is nothing to be afraid of.
2. Warm water
Axolotls are subtropical, and do not handle summer temperatures well. Most axolotls suffer from heat stress and will refuse food as their water reaches 23°C or higher. Heat stress in axolotls can be deadly, particularly at 24°C or above. I will be posting an article on how to cool your aquarium [coming soon!], but in the meantime, feel free to email me for advice.
3. Ammonia issues
Ammonia makes axolotls queasy, so they may refuse food or even throw up. If you’re keeping your axolotl in a tank, make sure your filter is properly cycled. In a tub, remember to do a full water change every day!
4. Problems with the food
Axolotls may ignore or spit food out when it’s too big, too hard, or it just has a nasty taste. Try cutting overlarge food in half. You can use scissors to cut up large earthworms, or a pill cutter to cut overlage pellets. Choose a pellet that softens rapidly in water. Avoid worms that taste bitter, such as red wigglers (Eisenia fetida). To avoid spoilage, don’t buy larger quantities of dry food than your axolotl can consume in approximately one month, and try to reseal the package properly after use. Don’t allow frozen food to thaw and then re-freeze.
5. Aggressive tankmates
If your axolotl is moving away from food or staying hidden at feeding times, they may be afraid that moving towards the food will draw in their neighbor’s wrath — especially if they’ve gotten nipped by them before. The solution is to feed the more aggressive axolotl in a separate container. If you’re worried about nipping at other times, it’s best to rehome the aggressive axolotl to another tank entirely.
If your axolotl refuses to eat for several days in a row, they may have swallowed something that caused a blockage. I will be writing a separate article on the issue [coming soon!], but in the meantime, feel free to email me if you need help with this issue.
1. Make sure the pellet is small enough for your axolotl’s mouth.
2. Wait until they are hungry!
3. If they are used to feeding from tongs or fingers, try this method first.
4. Try dropping the pellets one by one just above their nose, so that they are tempted to snap.
5. It’s normal for your axolotl to hesitate at first, and maybe even spit the pellet out. Even if they don’t go for it right away, leave one or two pellets in the water overnight. A good quality pellet will entice them by smell, and will usually be gone by morning.
6. If your axolotl still won’t try the pellets, don’t feed them their usual food until the next day — you don’t want to create a “if I ignore the pellet I will get my favorite treat” association!
7. Don’t try introducing pellets several days in a row. You should alternate with normal feedings, to make sure that your axolotl stays healthy and that their refusal to eat is not due to a different stressor, such as water quality issues.
8. If your axolotl still won’t touch the pellets on your third try, and they have no trouble eating other foods… Use a better pellet!
Dwarfism is a genetic condition which causes a foreshortening of the chest area and a smaller than usual adult size. Limbs may also appear shorter than usual, although the axolotl’s fingers and toes keep a normal appearance. Dwarfism can lead to health issues and shortened lifespans, particularly in females, due to the large number of eggs they carry. Dwarf axolotls should never be allowed to breed, and may need to be housed separately to avoid getting picked on by larger adults.
A mini axolotl is one whose growth stops before reaching adult size, which can be the result of genetic issues (often due to inbreeding) or stunting due to poor husbandry. Minis may be normally proportioned, or have a somewhat smaller than average tail, with normal chest and limbs. Just like dwarves, minis may require separate housing, and it is preferable not to breed them.
Short toes syndrome
Axolotls with short toes syndrome look similar to dwarves, but they have short fingers and toes that give their hands and feet a padded appearance. Over time, they develop a pudgy appearance due to oedema, an accumulation of interstitial fluid within the body tissues, which causes bloating of the entire body (pictured above). Short toes syndrome is a very serious and irreversible condition which invariably leads to painful oedema, hemorrhages and organ failure. To prevent unnecessary suffering, axolotls affected by this condition should be euthanized as soon as the condition is detected.
Whether you’re a beginner or an experienced aquarist, here’s why you should buy the BIGGEST tank you can afford.
1. It’s less work!
Larger tanks require fewer water changes. Having a larger tank allows you to use more filtration, which keeps your water cleaner longer.
2. It’s more forgiving of your mistakes
Everything is more stable when you’re dealing with a larger body of water: the temperature doesn’t fluctuate as much, pH is more likely to stay constant, and nitrogenous waste has less of an impact when there’s a lot of water to begin with. These three factors (temperature, pH and nitrogenous waste concentration) also affect the overall toxicity of ammonia (article coming soon!). This means that smaller setups are more likely to swing rapidly between non-toxic and toxic conditions. Some species such as freshwater shrimp are especially sensitive to sudden environmental changes, which makes them challenging to keep in a small environment.
3. Your animals will appreciate it.
A larger enclosure gives you the opportunity to provide a more natural environment for your animal. They will certainly appreciate the freedom of movement and the mental stimulation that a more complex environment can afford. An animal who is comfortable in their enclosure will reward you by displaying more natural behavior.
4. It helps them fight off viruses!
Larger tanks provide a temperature gradient — the surface is warmer than the bottom of the tank. One side may also be warmer than the other, depending on light positioning (and heater positioning, if you’re keeping tropical species). Having a temperature gradient in your tank allows your animals to adjust their body temperature, and even to self-medicate! Fish and amphibians are poikilotherms, which means their body temperature is meant to vary along with their environment. It also means that their bodies are not able to trigger a fever when they are sick. Instead, they rely on what we call behavioral fever: a sick animal will gravitate to the hottest area of the tank, act sluggish for a while, and wait for the virus or bacterial infection to pass. Amphibians are also particular in the way that they gravitate to colder temperatures when recovering from illnesses and injuries. Some scientific studies suggest that axolotls’ impressive recovery abilities function best at near-hibernation temperatures.