Species of the week: The Tammar Wallaby

Renowned worldwide as Australia’s iconic animal, the kangaroo is also of particular interest for a number of scientific reasons. 

This week, the first sequence of a kangaroo genome was completed. The species chosen for this project was the Tammar Wallaby (Macropus eugenii). The marsupial is the smallest wallaby species; when they are born, they are barely any larger than a single grain of rice, and they grow to be just 45cm tall. More significantly perhaps, the animal has a relatively small genome for a marsupial. Like other model species, such as the common mouse (Mus musculus) and thale cress (Arabidopsis thaliana) they are also easy to maintain.

So why study kangaroos? Mice are of use to many researchers who are studying human diseases and conditions, as their genome, physiology and development is very similar to ours.  Alternatively, kangaroos vary enormously from humans, and so arguably are of little use to biologists studying human genetics. However, they do represent a major branch on the evolutionary tree, where mammals and marsupials diverged 130 million years ago (though the recent discovery of an unusual fossil has put this time period under scrutiny). For obvious reasons, this is particularly fascinating for evolutionary biologists.

In addition, the genome sequence of the wallaby is of interest to immunologists and biochemists alike. Like all marsupials, the Tamar Wallaby gives birth to under-developed young, after just 4-5 weeks of gestation. New-born joeys crawl across their mothers’ front to reach her pouch, within which the infant latches onto a teat while it matures. Therefore, unlike mammals, marsupial infants are exposed to the environment whilst they are still in a very vulnerable condition. The content of the kangaroos’ milk has to compensate for this, and boost the joey’s immune system appropriately. Indeed, several years ago, a compound isolated from kangaroo milk was found to be 100x more effective than penicillin, and was effective in killing 99% of the micro-organisms it was tested against, which included bacteria as well as fungi. 

Image courtesy of bradypus

Sources used: http://goo.gl/PYFS3, http://goo.gl/HC70p, and http://goo.gl/1i1lW