On All Hallows’ Eve

You’re exploring a moonlit graveyard when something catches your eye — dozens of snails glowing softly in the shadows, all spiraling in the same peculiar direction. As a malacologist (that’s a snail scientist, for the uninitiated), you’d know immediately that you’ve stumbled upon something extraordinary. These aren’t ordinary garden snails. They’re all sinistral — left-handed — and in the world of gastropods, that’s about as rare as finding a unicorn.

This is exactly what happens to Lady Diana Starr in my novel, A GHOST IN AMBER. But before you run off to read about how she accidentally walks counterclockwise around an ancient yew tree and tumbles back through time, let’s explore the fascinating science behind what makes these left-spiraling shells so special.

Snail Coils

Have you ever noticed that most snail shells always curl in the same direction? It’s not random at all. A snail’s spiral forms early in development through a process called gastropod coiling. As the embryo grows, the snail’s body twists in a process called torsion, which makes the shell grow in a spiral and rearranges its organs to match. The end result is a coil that allows the snail tuck itself safely inside when danger strikes.

Most snails are what we call dextral, meaning their shells spiral to the right. If you hold a snail with the pointy tip (apex) up and the opening facing you, the opening will be on the right-hand side. Over 90% of snails are right-coiled like this, which makes it easy for them to find mates — everyone’s anatomy lines up the same way. It’s the “standard model” of snail design.

But sometimes, nature throws us a curveball: sinistral snails, whose shells spiral to the left. These lefties are rare, and their mirrored bodies can make it hard to mate with the right-handed majority. One famous example is Jeremy, a garden snail who made headlines in 2016 because he couldn’t find a compatible mate. Scientists launched a worldwide search and finally found him two left-coiled partners — a heartwarming (and scientifically fascinating) story that helped researchers study how coiling direction is inherited. 

How Snails Get Their “Handedness”

Coiling direction isn’t random — it’s coded in a snail’s DNA. In most species, the direction is controlled by a single gene expressed very early in the embryo. Here’s the twist: it’s mom’s genes, not the baby’s, that decide whether the shell will spiral right or left — something known as maternal effect. Left-coiling is usually a recessive trait, which is why sinistral snails like Jeremy are so rare. 

Scientists have pinpointed this remarkable trait to a gene called Lsdia1, which guides how a snail’s body establishes its left-right asymmetry through proteins known as formins. The mother’s genetic contribution sets the coiling direction before her offspring even begin their first cell divisions. Research by Reiko Kuroda’s team revealed that turning this gene off can flip the entire spiral — a tiny molecular change with dramatic consequences for the snail’s shape and reproductive fate.

Word Origins: Dextral vs. Sinistral

The terms we use for snail coiling actually come from Latin. Dextral comes from dexter, meaning “right” or “skillful” — it’s the same root we get “dexterity” from. Sinistral comes from sinister, meaning “left,” though in the past it also meant “unlucky” or “wrong.” (Medieval Europeans were suspicious of left-handedness.) Today, scientists use the words neutrally — no judgment implied — but they’re a great reminder of how language shapes our view of the natural world.

If it helps, you can think of dextral coiling as clockwise and sinistral as counterclockwise when you look at the shell from the top. That visual makes it easier to spot which kind of snail you’re holding.

Folklore Focus: Walking Widdershins

And here’s where things get a little spooky. In my book, A GHOST IN AMBER, a rare sinistral snail and a counterclockwise walk around an ancient yew tree pull our heroine back through time.

The word widdershins comes from Middle High German and literally means “against the way.” It refers to moving counterclockwise — the opposite of the sun’s path across the sky. In European folklore, this direction was linked to magic, mischief, and crossing into the otherworld. Witches were said to dance widdershins at their Sabbaths, and Halloween rituals sometimes used counterclockwise motion to summon spirits or break curses. Far from being purely sinister, widdershins was also seen as a way to undo bad luck — or to escape ordinary reality altogether. 

Lady Diana’s discovery of an entire colony of left-spiraling snails is no coincidence. These rare creatures, with their counterclockwise shells, are nature’s embodiment of the widdershins principle. When she wanders around the graveyard and the ancient yew tree—three times counterclockwise, as the old legend demands—she doesn’t just observe scientific curiosities. She becomes part of the magic.

When Science Becomes Enchantment

As a historical fantasy romance author, I love finding those moments where science intersects with folklore. The fact that Jeremy’s left-handed legacy helped modern geneticists understand heredity would have seemed like pure magic to a Victorian malacologist. And Lady Diana’s expertise — her ability to spot those sinistral shells in the moonlight — becomes the key that unlocks her greatest adventure.

Sometimes the most extraordinary discoveries happen when we pay attention to nature’s rebels: the left-handed snails, the counterclockwise walkers, the ones who dare to spiral against convention. In Jeremy’s case, being different led to worldwide fame and scientific breakthrough. For Lady Diana, it leads to something even more precious — a love that transcends time itself.

Anyone have plans to walk widdershins around an old tree in a graveyard this coming All Hallows’ Eve? Maybe play it safe and read  A GHOST IN AMBER  instead.

When Left is Right: Sinistral Snails, Widdershins, and Halloween Magic