Fascinating Digestive System of Snakes

Pictures like this aren’t exaggerations. How does a snake digest it? You’d probably say, “Like any other living thing”. You could not be more wrong, Carl Zimmer explains in Life’s Edge. When most mammals (include humans) digest food, their metabolic rate increases by almost 50%. For rattlesnakes though, it rises seven times. For pythons, it is even more extreme - it rises ten times. In fact, depending on the amount (by weight) that a python ate, it sometimes rose forty-five times.

 

But wait, there is one more comparison to make. The metabolic rate of a horse at full gallop rises thirty-five times. That means a python’s rate rose even more than a galloping horse… when it was doing nothing but digesting! Further, a horse can’t gallop at that rate for very long; whereas a python can keep at that metabolic rate for the two weeks it might take to digest its food. All this makes it clear that there’s something very different in how snakes digest their food, even when the prey is not as outsized as the pic above.

 

The more Stephen Secor studied this, the weirder it got. Our stomachs release hydrochloric acid a few times a day since we eat multiple meals. But a snake eats rarely – so its stomach is neutral most of the time. But when it starts to gobble its prey, its stomach releases a flood of hydrochloric acid to digest.

 

The abrupt change wasn’t just within the stomach. Its small intestines double in mass overnight to absorb the upcoming nutrients. The liver and kidneys also double in weight to store the nutrients and expel the waste. The heart grows 40% to push the extra load of sugar and other nutrients around the body.

 

How was such a rapid change in the internals possible? After all:

“They have the same anatomy and biochemistry as other vertebrate animals.”

Nothing, not even their genes, are so different from other vertebrates. Secor suspected the snake’s genes operate differently. Some genes, remember, can act as switches to turn on other sequences, which then set off yet more sequences. Secor suspected maybe 20-30 genes were involved in the transformation of snakes. The actual number stunned him – it was over a thousand. Many of these genes worked through ancient pathways in the body, pathways shared with so many other species. Except, in most other species, those pathways lead to growth of the animal. The snake, it turns out, can use those pathways not to grow itself, but to grow individual organs within itself.

 

Such rapid growth has its costs. Their cells grow too quickly, sometimes producing deformed proteins. Charged molecules fly around the cell, with potential to damage their DNA. Fixing this damage caused by such growth increases the metabolic rate even more.

 

All in all, such an insanely high metabolic rate means roughly a third of the energy from the prey is used up by the snake in digesting it. Once the food is digested, the internals restore themselves to their original sizes. And then the cycle repeats itself at the next meal.

 

Life is very strange – the snake doesn’t have any significantly different genes from other vertebrates, yet its metabolic system is unlike that of every other species we know of.

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