Weird Lab Mice

I found this interesting blog post, which highlights some of the weirdest mice used in research. Not exactly the most pleasant images but each mice plays an important part in scientific research.

Intrigued? Take a look…. ‘The 8 Weirdest Mice in Research’

The Nude Mouse – lacks an immune system which allows it to be used for tissue and tumor transplantation.


The Bruce Effect

I regularly control the breeding of mice in my day job and have always been told not to introduce a new male to the cage when the female is pregnant. Wondering why this rule existed I did some research and came across the Bruce Effect. The Bruce Effect is old news. It was first described in 1959 by Hilda M. Bruce, a British zoologist with a keen interest in rodent sexual behaviours.

The Bruce Effect describes the phenomenon of female rodents terminating their pregnancies when they are exposed to an unfamiliar male. The effect is controlled by pheromones. The pheromones secreted by the males leads to a reduction in the production of prolactin, a hormone required for progesterone production. Progesterone is required to maintain pregnancy, therefore a drop in progesterone will lead to a miscarriage. The female then ovulates and allows a new embryo to be conceived.

There are clearly evolutionary reasons why the Bruce Effect exists. How can you explain the evolutionary benefits of aborting your own offspring? One hypothesis is that the male does not want to waste its time and energy bringing up offspring who are genetically not related and therefore not containing the male’s DNA. Another hypothesis, favours the female. The male will most likely kill the offspring when they are born if they are not genetically similar. Therefore, the female doesn’t waste her energy going through the whole pregnancy and aborts sooner rather than later.

Although the effect is most commonly reported in mice, it has also been found in other species such as monkeys. I wonder what other species may possibly display the Bruce Effect? What about humans?