For many of us mere humans at Earlham Institute, even withstanding temperatures above 25 degrees is a formidable task. Not so for desert mice, which can tolerate extreme environments and temperatures up to 42 degrees Celsius - taking it all in their tiny stride.
David Thybert, research Fellow at EI, has focused his work on understanding how rodents are able to withstand incredibly extreme arid environments such as deserts - and thrive in situations that are completely inhospitable for most forms of life, let alone mammals.
The tricks to their tolerance can, as is so often the case, be found nested within their uniquely-attuned genomes - and can also provide hints to the basis of human conditions such as obesity and diabetes.
Life at the limits.
Deserts are pretty inhospitable places. Even plants struggle to get a stranglehold in such environments - and the life that does exist in these arid places is sparse compared to more lush, rainy regions such as rainforests and grasslands.
Still, life finds a way, and among the hardy beasts that call the desert home are several species of rodent, which are very well adapted to tolerate the challenges that accompany life under the baking hot sun.
It’s of no real surprise that such organisms have come to colonise arid, or xeric, environments (those lacking moisture), as they form the Earth’s largest terrestrial ecosystem - covering almost one third of the world’s land mass.
In terms of studying how organisms can adapt to extreme conditions, rodents present an interesting model organism due to their diversity in terms of species and variety of phenotypes even in closely related species - but also because of their alternative methods of withstanding hardship.
Three (not-so) blind mice.
One model, for example, is the Algerian mouse, Mus
As a nocturnal animal, the Algerian mouse comes out at night to avoid the warmer temperatures of a Mediterranean summer, and can drink two-thirds less water and can stand higher temperature than the domestic mouse, which goes some way to helping it survive in a semi-arid environment.
To understand how the Algerian mouse became more adapted to arid condition, David is sampling DNA from wild Mus
The nocturnal Cairo spiny mouse, Acomys
Mice to human.
Of even greater interest to science, A.
However, when it comes to living in captivity this can pose a health hazard - and A.
In the Western world, obesity and
The interesting phenotypes of Acomys do not end here. They are able to regenerate tissues like skin and cartilage. This is the first recorded instance of this in any mammals, for that matter.
Science has never really before had a mammals model to study tissues regeneration, thus further study into these tiny spiny mice might
Nano-mice from Mars.
Mice are not from Mars, but like Earth and Mars, albeit from cells and nucleic acids rather than dust clouds, the Nannomys mice diverged from a common ancestor to house mice (Mus musculus) around three to six million years ago.
The Nannomys, also known as African pygmy mice, are a miniscule five grams and represent some of the smallest rodents on earth.
Two such rodents are of interest to study in terms of how species adapt to different environments. Mus indutus, the desert pygmy mouse, colonises the Kalahari desert - and as such is adapted to tolerate an extremely arid environment.
Another species, Mus minutoides, thrives in a grassland environment - and the two species diverged two million years ago may be sympatric i.e. they inhabit the same geographic region.
Such species are interesting to study in terms of direct comparison, as we can hope to find the specific genetic regions present in Mus indutus that helps them prosper in a more arid environment than their closely related cousins.
More than one billion people live in desert regions, despite us being poorly adapted, biologically, to this environment.
Nano-mice from Mars.
Another interesting feature of Mus minutoides is that it appears to undergo a reversal of sex determination, straying away from the classic XX/XY, which is extremely rare for a mammalian species. Indeed, there exists a high proportion of fertile females that present as XY rather than XX.
Indeed, in some populations a whopping 74% of female Mus minutoides are XY. It turns out that there is quite a diversity within the X chromosome of these pygmy mice, with morphologically different X chromosomes causing this sex reversal. As such a rare example within mammals, these mice therefore present an interesting case to study determination of sex in all mammalian species.
With over 1500 species, the rodent present the most diverse group of mammals to study. Considering their close evolutionary ties,they are especially interesting to study in terms of adaptation to different environments and niches.
Furthermore, with their suite of interesting phenotypes, including many directly relevant to diseases that present in humans, the study of rodents might help us to further dissect how our own bodies function and inform us of how to combat such emergent illnesses as diabetes and obesity, which are becoming ever-more present in the 21st Century.
“With their wide distribution all over the world and their diversity of phenotypes even between closely related species, rodents are ideal models to understand how mammals evolve and adapt to new environments,” said David
*Image at the top of the article provided by Frederic Veyrunes.