Genetics

Genetics in African Pygmy Hedgehogs have never been fully researched. There was a chart with some guesses at genes, but it never got off the ground. In 2015 we decided to set up a study in genetics and, eventually, produce a fully researched and clear color guide.

* This guide on genetics is built with the help of De Grote Cavia and we have their full approval of using their explanation to build our guide. 

Why is the knowledge of genetics so important?

The species is based on just a small group of hedgehogs that were exported from the wild to be held as pets. All of our pet hedgehogs are born out of those hedgehogs and that makes it a very small, unstable gene pool. When you start breeding with an unstable gene pool, it creates a species of pets with many health problems, as we see clearly in African Pygmy Hedgehogs. Wobbly Hedgehog Syndrome (WHS), diabetes, obesity, kidney diseases, and others, are all health issues that are widely known in this species.

Eventually, when breeding with that small and unstable gene pool, the color lines start to develop and, after a few years, they will become stable. But the health issues remain and, after so long, nobody really knows where the issues started exactly. Did they come with certain colors that popped up over time or is it just a general weakness? Nobody really knows. And that is where genetics start to be a solution. When the genes which determine the color are known you can start another research. A research where you collect a list of hedgehogs with health issues and which colors they have. With that list it is just a simple search game to find that one piece of the puzzle and see if the issues are linked to colors or if they are specific to hedgehogs only. Maybe even specify one species of hedgehogs: African Pygmy Hedgehogs!

By ruling out a color that causes these health problems to come through, you can improve the health of the animals in the next generation and thereby the entire species. Well, if it’s that easy…

Do you have an example?

Yes, we sure do! Although there are multiple examples to give, we’ll take Megacolon in rats. Megacolon is a hereditary bowel disease. It’s a defect of the nerves between the intestines and the brains, causing a loss of control of the intestines. The symptoms can differ, but the outcome remains the same: the rat will die.

Megacolon is a hereditary disease, but rats with a heavily white coat are prone to have it. It’s likely that the disturbance in the production of pigment has influenced the formation of the intestinal tract. The rat that is born has no normal bowel function and is unable to defecate, this causes severe consequences.

Breeders are aware of the fact that rats with the color Husky are prone to this bowel disease and will observe their offspring continuously. When a litter is born with this disease, most breeders will end that bloodline and never breed with it again. This way, their lines stay healthy.

Rats with color ‘Husky’ – Photo’s by Danielle Olree


What is genetics?

Genetics is the knowledge of inheritance. That means that it comprehends how characteristics from parents to their kids are passed on. Tall people, most of the time, get tall children. People with dark hair, usually get children with dark hair. That is genetics. The tall parents have cells in their body that can pass on the characteristic for a tall body to their children.  Those cells are called ‘genes’.
Those genes are found through the entire body as well as the oocytes of a woman and the sperm of a man. If such an ovum of a tall woman and a sperm cell of a tall man collide and merge together to become one cell, that cell will contain the characteristic ‘length’. And because the information is transferred from two tall parents, that gene will tell the cell to create a tall body.

Genetics in African Pygmy Hedgehogs

Genetics in people and other animals is similar. Two bigger animals well often get bigger offspring. Two Black hedgehogs will often get black offspring. I say “often”, because you cannot simply go off their looks. The genes with information on the characteristics are found on the inside and you cannot see them.
If you’re wondering “But if I have two Black hedgehogs, then I can see that they are Black so why wouldn’t they give Black offspring?”, then this is easy to answer. This is because some characteristics are seen on the outside and some of them are not visible. A hedgehog can be Black and still produce Albino offspring. They can have genes for Black as well as for Albino, without you seeing it on the outside. That can happen because there are dominant as well as recessive characteristics.

Dominant genes are.. well, dominant. Recessive genes are always a bit on the background. A dominant gene will always be visible, while a recessive gene only appears if it’s not being suppressed by a dominant gene.
A hedgehog has a gene package in which determines the color of its skin, quills, eyes and mask. With a Black hedgehogs, that’s all black. But there can be a hidden color within that package, for example Albino. The Black is visible, but the white Albino is not.

Genetic packages

Let’s imagine the gene packages as little circles. Each package has the option to store two colors. In the left package these two parts are Grey. The middle package holds one half grey and one half white. The right package holds only white. If we imagine the left package as a hedgehog, it would be a Grey hedgehog and the hedgehog with the right package would be an Albino.

A hedgehog with the Grey color doesn’t only have this color, but it also can give nothing else but Grey to its offspring. It doesn’t have anything else to pass on. We call this a ‘pure bred’ for color, which means that it contains only this color and can only pass this color on to its offspring. A white hedgehog with only white in its gene package, is also pure bred colored hedgehog and this is true for every other color.

Crossing purebred African Pygmy Hedgehogs

If we were to cross these two pure bred colored hedgehogs with each other -the pure bred Grey and pure bred White- to get offspring, their children will all look like Grey hedgehogs. No matter how many, they will all be Grey. The white seems to be completely lost, but it’s not. It’s inside of the Grey offspring, but it’s not visible on the outside.

If we look at the crossing with the gene packages, it wil make some more sense. Each parent only gives one half of its package to its offspring, to merge together with the half of their mate. Logically, their young will get one grey half from the Grey parent and one white halve from the Albino parent. Merged together to one cell in each of their offspring, all of their children will have one Grey half and one white half in their gene package.

 x 

 

 

Genotype & phenotype

The fact that you can see the grey on the offspring but you can’t see the white, even though it’s still inside them, is the difference between genotype and phenotype. The genotype is what the hedgehogs have written down in their gene packages, phenotype is what we see on the outside.

In case of a Grey hedgehog, which has both grey and white in his gene package, the genotype has those two different halves in his gene package.
The phenotype, however, is Grey. That is what we see on the outside. The white on these hedgehogs is not visible, but it can be passed on to its offspring.

This hedgehog is not a pure bred for color. If you want only Grey hedgehogs, than there’s no value in a hedgehog that can give both Grey and Albino to its offspring. You would want a hedgehog that can only pass on its Grey color.

So, on the outside it’s impossible to see if a hedgehog is a pure bred. That’s where the pedigree comes in handy, because you can see which colors its parents, grandparents and even further down the lineage, are. If they are all Grey, chances are it’s a pure bred. But if there’s even one ancestor with a different color, the chance is that the hedgehog is not a pure bred. You can breed for generations on end and still have not a single pure bred hedgehog.

Ratio 1:2:1

That is possible because of a trick of Mother Nature. Genetics has a ratio that it follows. Mendel discovered this with his research with green peas. The ratio is 1:2:1. But we’ll explain that for you so you don’t have to read his entire research.

When you get a hedgehog from pure bred Albino and purebred Grey parents and you mate it with its sister who also has the two colors in it’s gene package (which is NOT recommended as inbreeding is a definite no-no, but this is just an example), you’ll get a combination of their gene packages. Because both parents in this case have both a grey and a white half in their gene packages, this is mixed into their offspring. And that always happens in a 1:2:1 ratio. It means that you’ll get the following offspring in their litter:

1 pure bred hedgehog with a grey/grey gene package Visible color: Grey
1 pure bred hedgehog with a white/white gene package Visible color: Albino
2 hedgehogs with a grey/white gene package Visible color: Grey

  x  

 

 

 


In this offspring, it’s easy to spot the only animal we know for sure is a pure bred: the Albino. But in the Grey hedgehogs, only one of them can be a pure bred and the other two are not. But you don’t know which one is the pure bred. The only way to see if they are, is to let them have offspring. If there is Albino in that litter, it’s not a pure bred hedgehog. However, the funny thing is, is you don’t get Albino from its litter, you still don’t know if it really is a pure bred. You can repeat this for generations and still have a hedgehog with a mixed gene package.
That’s all due to the ratio of 1:2:1 and to Mother Nature’s trick.

If you have smaller litters, the chance of having this ratio gets smaller. I you have two offspring each time, chances are they both end up Grey: one pure bred and one mixed. But even if you do get big litters, it’s still up to Mother Nature. You can get 6 Grey hedgehog in a litter of 7 or even three Albino’s in a litter of 4. A recessive characteristic like Albino, can be carried for generations without coming to the surface. Better to say, the ratio applies to each born hoglet rather than to the entire litter. In this case, a hoglet has 25% chance of being a purebred Grey, 50% of being a mixed bred Grey and 25% of being a purebred white.

But even though we’ve been through it all, we still don’t know why colors inherit in ways like this. What is all that about? Well, that’s due to different forms of inheritance. Some colors can be dominant or recessive. In this example, grey is dominant over white. So if there is either one or two grey halves in a gene package, the hedgehog will turn Grey on the outside. Only if both halves are white, the hedgehog will be a visible Albino.

Genetic symbols

In genetics, a characteritics is always noted in two parts, like we made in the examples above with the circles. But instead of using circles, we use letters to describe their genetic traits. Like the following:

  • Grey-Grey
  • White-White
  • Grey-White

These are the only possibilities in our example. However, it’s more convenient to note which trait is dominant and which is recessive. Grey is dominant over white and we like to note dominant traits as capital letters. This way it’s easily seen which trait is dominant and which one isn’t. So now it looks like this:

  • GREY-GREY
  • white-white
  • GREY-white

It still is a lot to write down this way, so in the genetics community it’s common to use symbols to note the traits: we use letters. A dominant trait is noted as a capital letter, a recessive trait as a small letter. Just like the previous explanation. For Grey and Albino in this example, it would look like this:

  • G-G
  • w-w
  • G-w

However, in genetics there are no dashes used between the two halves. So this becomes:

  • GG
  • ww
  • Gw

And here it gets a bit more complicated, because Mendel hasn’t researched the grey and albino colors in hedgehogs, but he just started with using the alphabet as a guideline to note down genes. How fun this entire chapter was, it’s not the reality of the genetic symbols used in hedgehogs.

The genetic code for Grey is: AABBCCddPP. For Albino it is: AABBccDDPP. Shortened out, Grey would have the genetic code ‘dd’ and Albino has the genetic code ‘cc’, because it would save us from writing down a number of other genes that might not have any influence in future litters, in case of a purebred. Carried genes are noted down when applicable, so a Grey that carries for Albino like we discussed earlier, would be written down as ‘Cc dd’ and an albino carrying for Grey would have the genetic code ‘cc Dd’. This way it’s easy to see which hedgehog carries for which colors.

A list of colors and their genetic codes are found in the color guide with picture and a small explanation, but we also made an explanation of each genetic color mutation on this page.

If you want to know more about the forms of inheritance, you can check out this page.