Snakes are survivors, and are capable of routinely going weeks, sometimes even months, without a single meal.
A new study has finally pointed to how they do it.
The fresh genetic discovery offers one clue to snakes’ impressive fasting ability. The findings have pointed out that many snakes are completely missing the gene called ghrelin, the hormone long nicknamed the “hunger hormone.”
WHAT IS THE HUNGER HORMONE MISSING IN SNAKES?
Ghrelin is a hormone mainly produced in the stomach that signals the brain to stimulate appetite.
Often called the “hunger hormone,” it rises before meals to encourage eating and drops after food is consumed.
Beyond appetite, ghrelin also influences metabolism, fat storage, insulin sensitivity, and even growth hormone release in mammals.
In the case of ghrelin not functioning normally or, as in this case, being absent, a creature loses completely the ability to feel hunger.
WHY DON’T SNAKES GET HUNGRY?
Scientists examined the genomes of 112 reptile species, ranging from snakes and crocodiles to chameleons.
They found that both the ghrelin gene and the gene for MBOAT4, the enzyme needed to activate ghrelin, are both absent in 32 snake species, especially in groups such as the largest family of snakes with over 200 genera, called the Colubridae family.
The absence, however, wasn’t exclusive to snakes.
Certain chameleons and toadhead agama lizards, which normally feed more often, also lack these genes.
In contrast, crocodiles, which are animals capable of fasting for over a year, still carry both genes intact.
The research, led by Rui Pinto and Rute Fonseca, was published in the journal Open Biology.
DOES LOSING GHRELIN CAUSE HUNGER?
Well, not necessarily. In mammals, ghrelin’s link to appetite is more complicated than once thought.
Experiments show that mice without the ghrelin gene eat normally and maintain typical body weight. Even more puzzling, in both mice and humans, levels of active ghrelin and its activating enzyme often increase after a meal begins, the reverse of what a pure hunger signal would do.
Rui Pinto, from the Interdisciplinary Centre of Marine and Environmental Research in Porto, Portugal, believes the explanation lies elsewhere.
He suggested that the hormone’s absence likely relates to the snakes’ unusual metabolic needs, such as fat storage and insulin regulation, which may work very differently in reptiles with such slow energy use.
HOW ARE EXPERTS REACTING?
Evolutionary geneticist Todd Castoe of the University of Texas at Arlington, who was not part of the study, described the finding as “striking.”
He noted that many researchers, including himself, had overlooked this patter, until now.
Tobias Wang, a zoophysiologist at Aarhus University in Denmark, urged caution about ghrelin’s metabolic importance.
Rute Fonseca, an evolutionary geneticist at the University of Copenhagen and co-author of the paper, agreed the current genomic work is only a starting point.
She stressed the need for more detailed experiments, like removing the ghrelin gene from crocodiles or supplying the hormone to snakes. Doing so, she said, could help understand the hormone’s true role in different species.
