Burmese pythons can grow up to 19 feet (almost six metres) in length. Such a big body requires big meals. They eat prey as large as cattle – and they eat them whole. No tearing into bite-size chunks, no chewing. Everything goes down all at once, bones and all.
Snakes that are fed a boneless diet suffer from calcium deficiency, so digesting skeletons is important for their health. But how they avoid absorbing too much calcium, and suffering from calcium toxicity as a result, has remained a mystery - especially as no bone fragments ever seem to come out the other end.
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To solve this mystery, Dr Jehan-Hervé Lignot and his colleagues examined the intestines of these mega-snakes in a new study.
In the lining of Burmese python intestines, the researchers discovered a new type of cell. These cells are narrower than the usual cells found in the intestinal lining, and have special folds in them called crypts. It is these crypts that hold the secret to how snakes avoid being overloaded with calcium: they store molecules of calcium – as well as phosphorus – within them, therefore stopping these molecules from being absorbed.
The researchers can be sure that these calcium and phosphorus molecules come from excesses in the snakes’ diet because they ran an experiment.
They fed one group of pythons with whole prey, one group with boneless prey, and one group with boneless prey that had been injected with calcium.
Empty cell crypts were only seen in the group that had been fed boneless prey, showing that these crypts fill up with excess calcium and phosphorus from the snakes’ diet.
When the team looked in the intestines of other reptiles that gulp down entire animals – such as other pythons, boas, and the venomous Gila monster – they found the same sorts of cellslining their intestines.
Snakes and lizards are not the only animals that eat the entirety of their prey, though. Many carnivores swallow skeletons, from crocs to sharks to birds such as the bearded vulture. How these animals avoid being overloaded with calcium is still up for debate, but it could be that they have these specialised cells – or cells like them – in their intestinal linings, too.
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