Female Moles And Their Mysterious Genetic Conspiracy

by Nadia Sheikh

Female Moles And Their Mysterious Genetic Conspiracy

April 16, 2021

For a faceoff in the world of moles, you literally need to grow a pair of balls, regardless of whether you’re male or female. One of the biggest mysteries in the world of genetics is in the gene regulations of the female moles, who have testicles and ovaries both. Nature allows them the ability of not having to compromise during a battle by giving them the male organ, allowing them to be triggered and just be unnecessarily aggressive to win the arguments in the mole world (and we know that the male organ works in the same way in the human world and perhaps even in the world of butterflies)

The life of moles is quite hectic and tough and they know if they’re ever stuck in a faceoff, dominance needs to be asserted via aggressive means. So nature has made it possible for even the female moles to quite literally grow a pair of balls.

Let’s Take A Look At The Genetics

Ideally in mammals sexual development only goes one of two ways, progression towards being a female or a male, there is no in-between.

For mammals, two types of sex chromosomes exist that determine the gender of the offspring. The X chromosome and the Y chromosome. Since chromosomes are arranged in pairs, the two types of pairs are XX and XY, the former being the determinant for a female and the latter being the determinant for a male. Females only have X chromosomes in all their reproductive cells as well, while the males have both X and Y types of cells. Basically, all this science jargon is to explain to you that in order for a testicle or a male organ to exist, the presence of a Y chromosome is integral.

Female Moles In The Story

For moles, however, things are slightly different. Nature has gifted the female moles with the presence of both the sexual organs. They have testicles tacked on to their ovaries, calling this complex and intriguing feature the ovotestes. What’s interesting is that in order for the testicle to even exist, the presence of a Y chromosome in the mole is very important, however, not even one female mole has shown any variation in their sex chromosomes. They only have X chromosomes as the norm for the female gender usually states.

image 2 11
Side views of male and female broad‐footed mole (A‐C) and mouse (D & E) external genitalia. (F) The external genitalia of the breeding season female broad‐footed mole shown in (C), but at a ¾ side view showing the vaginal opening with forceps inserted

How Is This Even Possible?

While a lot about this exception in how genes function still remains a mystery, what we know for now is that the variable exists but in the gene regulatory factors of the chromosome. Gene regulatory factors are components that determine the expression of certain genes and the degree of those expressions as well.

This ovotestis does not compromise or modify the reproductive capabilities of moles in any way and it functions just like a regular ovary that releases eggs for maturation and then eventually reproduction. This testicle does not make the female moles reproductively independent since it does not produce any sperm cells

Transverse sections of the external genitalia of the male and female mouse (A & B) and broad‐footed mole (C & D). See red arrows in Figure 1 for the approximate level from which the sections were taken.

Role Of Testicle?

It produces Leydig cells. These Leydig cells help in the production of hormones called Androgens that help in the release of testosterone and androstenedione. Popularly and wrongly classified as the “male hormone”. Yes, it is abundant in males but that does not mean that it is entirely absent from the female body.

We know that all female mammals, in general, may have some amount of testosterone in their bodies however this testicle supplies the hormone in the amount that would ideally be generated in male animals, giving the female a better display of aggression if needed during a fight.

For this observation, there are still many ongoing studies by geneticists who are still trying to figure out how this is even possible. Mother nature works in mysterious ways and that’s all we can say about it right now.


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