Monday, July 5, 2010

For those that know me, whether in person or through my many multimedia outlets, they will know that I have a deep enthusiasm and interest in reptiles, especially snakes. Therefore, it should come as no surprise that I would write about them eventually.

I have handled, fed and cared for many species, and I have also been bitten on more than just one occasion. But, I know that it was not their fault, it was mine. They were just doing what came naturally to them.

It is commonly known that snakes, specifically pythons, will constrict prey and suffocate it, before swallowing it whole and digesting it slowly over a period of days. However, what happens to the prey once digested? And how does the snake's physiology change in order to accommodate it?

The Burmese python (Python molurus) is what is known as a 'sit and wait' predator, where it expends the very minimum amount of energy hunting its prey, so that it can survive long periods without food. However, since the organ systems within the python are operating at such a low capacity to conserve as much energy as possible, a huge increase in energy must be required in order to start extracting nutrients from its newly digested prey.

At the annual meeting from the Society for Experimental Biology in Prague, Czech Republic, researchers used both CT (computer tomography) and MRI (magnetic resonance imaging) scans to observe the digestion process of a 5kg Burmese python.



The images were taken both before and during digestion of a rat at pre-set time periods (at the two, 16, 24, 40, 48, 72 and 132 hour mark), in order to view the whole digestion process. What the scientists discovered was that numerous physiological changes were occurring within the snake while it began digesting the rat: Its intestine expanded, its gall bladder shrank, and its heart increased in volume by a shocking 25 per cent.

The researchers from the Aarhus University in Denmark, Henrik Lauridsen and Kasper Hansen, stated that they believe the shocking increase in the size of the snake's heart was most likely associated with the increased energy requirement needed to digest its meal. The only way to access the energy required was by increasing blood flow above what the normal sized heart could provide, hence its sudden enlargement.

Lauridsen told the BBC News that since the snake can eat up to 50 per cent of its own body weight with one meal, it is important "in order to get the energy out of the meal, it has to restart the intestinal system very fast."

According to Hansen, this type of technology would allow for a clearer view than what normal dissections are able to provide, which can often be subjective as they can often induce changes within the specimen itself. "For example," said Hansen, "after opening the dense bone of a turtle shell, the lungs will collapse due to the change in pressure."

This new technology also has one major advantage over dissections (which are still useful), the CT and MRI scans cause no harm to the snake, and the data can be revisited over and over again in its digital form.

The two pictures below show that by injecting different contrasting agents into the specimen, the researchers were able to highlight specific organs with a specific color, in order to mark changes throughout the digestion process. The first picture shows the musculature and tissue organization within the python, and the second demonstrates how different contrasting agents allow for a unique color coded view of a specimen (in this case, an alligator).





For the link to the original BBC article, click here.

If you're interested in a video of what a python looks like digesting its prey, click here to watch a video of a large python eating a deer. CAUTION - May disturb some viewers.

Also, here is a paper from 2008 dealing with the predatory habits and the digestive physiology of the Burmese python. If you're interested, it was a fascinating read!