Scientists discover why snake embryos always coil to the right
The mystery behind snake embryos' right-handed coiling has been solved.
1The mysterious coil of snake embryos
Snake embryos have the longest body structure among vertebrates, made possible by tight spiral coils during embryonic development. Researchers have long wondered why these coils always form to the right. Zoologist Alexandra Weber from the University of British Columbia notes they are just beginning to understand how such spiral shapes form in animals.
2Research initiated during the pandemic
During the 2020 COVID lockdowns, evolutionary biologist Tetsuto Miyashita at the Canadian Museum of Nature in Ottawa was searching for a remote research project for his students. Remembering his PhD advisor's interest in evolutionary asymmetries in snakes, he collected images of over 900 embryos from 39 snake and limbless reptile species.
3Striking biological pattern
Miyashita and his students discovered a striking biological pattern when examining embryo images: snakes begin coiling to the right in the first weeks of embryonic development, even before muscles form. Weber stated that different forces create this coiling, but they didn't know the exact mechanism.
4New discovery through CT scans
CT scans revealed a previously unidentified biological structure: an intestine located outside the embryo's body but enveloped by blood vessels stretching from the yolk. According to Miyashita, this 'pillar of gut' slowly detaches from the yolk while tethering the elongating body. Since the yolk is always on the embryo's left side, the snake coils rightward.
5Simple explanation of the mechanism
Miyashita compares this dynamic to adjusting a strap's length—the longer, buckling loop always twists in a particular direction. As the snake embryo develops and gains muscles, about half of late-stage embryos recoil to the left.
6New perspective in evolutionary biology
Many evolutionary biologists had focused on genetic analyses to explain snakes' unique anatomy. Miyashita expressed gratitude for these 'key discoveries' but emphasized that answers can sometimes be found through simple observation skills. He noted they uncovered snakes' secret during COVID lockdowns with a surprisingly straightforward approach.
7Scientific publication of the research
The research team published their findings in Current Biology. The study demonstrates the importance of careful anatomical examination to understand snake embryos' coiling mechanism. Miyashita says even recording which way snake embryos coil and closely examining their anatomy can yield significant results.
8New horizons in biology
This discovery raises new questions about snakes' evolutionary development. Researchers plan to investigate whether similar mechanisms exist in other reptiles' embryonic coils. The findings could contribute to understanding asymmetries in vertebrate embryonic development.