This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An international team led by Canadian researchers has found evidence explaining why snake embryos form a curious spiral. This ability to coil as embryos enables snakes to hatch with the longest bodies of all vertebrates.
The study, published in the journal Current Biology, reports that snake embryos coil into a right-handed spiral as their long bodies grow while tethered by the gut. "It's like when you adjust the length of a strap and the longer, buckling side of the loop twists," explains senior author and team leader Dr. Tetsuto Miyashita, an evolutionary biologist at the Canadian Museum of Nature.
"There is a touch of mystery to spirals, and we are only beginning to understand how these shapes are produced in animals, such as our looping intestine, snail shells and now these beautifully coiled snake embryos," says lead author Alexandra Weber, now a graduate student in zoology at the University of British Columbia. Miyashita adds, "These puzzles beckon our curiosity. After all, spiral forms in nature have inspired human creations ranging from rotini pasta to a barber's pole or even portrayals of the biblical 'Tower of Babel.'" The effort to solve the mystery of coiling snakes was born out of the COVID-induced lockdown in 2020.
Miyashita recalls being in his home office, trying to come up with a research project that his students could do without going to the lab or museum. "Then the light bulb went on. I had inherited from my Ph.D. adviser this fascination with asymmetries in animal forms.
So every time I saw images of snake embryos in papers, I wondered whether they are right- or left-handed in their coiling." With this idea in mind, Miyashita instructed Weber, then at Carleton University, and two other undergraduate students at the University of Ottawa to send emails and hunt for pictures of snake embryos in the literature and in databases of museum collections. "We obtained pictures of more than 900 embryos from 39 species of snakes and other limbless squamates. That's a statistically robust sample." The team observed that for the first few weeks after eggs are laid, snake embryos seem to coil only dextrally, or right-handed, from head to tail.
"At these stages, the embryos don't have muscles to move with, so different forces are making them coil right-handed," Weber explains. "But we didn't know what was making them do that." To solve this puzzle, Dr. Raul Diaz, their collaborator at California State University Los Angeles, subjected snake embryos to CT scans and made an interesting observation.
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