East Coast - Purple Worth More Than Gold
Today we continue to explore the maritime intertidal. It’s a vibrants spectrum of animals, plants and, particularly relevant for us, colours. Because we’re going to use clutches of pink eggs and a bright orange whelk to find out how purple can be worth more than gold.
EPISODE NOTES
I mention in the episode that Phoenicia may have been the original place where people figured out you could make purple dye from whelks. Just how important was that at the time? Phonecia is the name given to the region by the Greeks, and it’s thought to have literally translated as ‘land of purple’.
The Victorian chemist who was the first person to (accidentally) synthesize purple dye via coal tar was William Henry Perkin. He was trying to make quinine so the British wouldn’t have to rely on the cinchona tree for production of antimalarials. The quinine experiment failed but he’d go down in history, and change the whole course of his career, because of his discovery.
TRANSCRIPT
Twice a day in the Bay of Fundy, more than a hundred billion tons of water recede to expose a vast expanse of ocean floor.
Striking out across it gives you a totally unique perspective on an ecosystem full of plants and animals that have to be adaptable to their whole world routinely turning upside down.
And with each low tide, you’re never sure what you’re going to find. It’s an ever-changing, always vibrant spectrum of flora, fauna and, yes, colours.
For example - these clusters of sometimes bright pink little eggs stuck to the sides of rocks. And the sometimes bright orange gastropods who lay them.
They are dog whelks. Very common but very fascinating. They have done real well for themselves, spreading wide across both sides of the North Atlantic.
Unlike most snails who forage for food and scrape algae off rocks, whelks are actually carnivorous. And they have a pretty gnarly way of feeding.
Their foods of choice are mussels and barnacles, both with the convenience of not being able to escape. The whelk uses a specialized organ called a radula - sort of like a toothed tongue - to scrape a little hole in its prey’s shell.
Once the hole is made, the whelk uses a second specialized organ on its foot to secrete paralyzing chemicals and digestive enzymes into the hole. This basically reduces the victim to a soup that the whelk can slurp up with a proboscis.
So… gross. But there’s a reason I’m putting you through this. Because that paralyzing, digesting… secretion? It was once literally worth more than gold.
Pink. Orange. But for centuries, the colour most associated with whelks has been… purple.
Purple, historically, has been the colour of royalty. But… why exactly is that?
Well, if you are royalty, you’d want your signature colour to be something… exclusive. Unavailable. Hard to come by.
Turns out purple fit the bill, because the only way to get it… was from these guys.
At least as early as 1570 BC, Phonecians had figured out a process of extracting purple dye from whelks.
And this was not a straightforward process. You needed to get the aforementioned secretion from the whelk’s hypobranchial gland, either by ‘milking’ the whelk by scaring it - which you can do repeatedly, or just by unceremoniously smashing them.
And from that you get… almost nothing. A miniscule drop of milky colourless mucous. But when you expose it to the sun and the air, it magically cycles through a series of colours - from yellow to green to blue and finally, purple, where it stays and lasts.
Archaeologists have found vast piles of smashed up whelks from ancient dye-extraction operations. It took up to 12,000 whelks to produce 1 gram of dye.
Exclusive. Unavailable. Hard to come by.
In Rome it was called Imperial or ‘Tyrian’ purple. The Caesars declared it their official colour with exclusive rights to its production.
By the 4th century AD only the Roman Emperor was permitted to wear it. It became a metonym for Emperor-hood, the phrase ‘donned the purple’ meant ‘became Emperor’. An heir to an emperor was said to be ‘born in the purple’.
People have called it the oldest known pigment, the longest lasting, the product of the first chemical industry, and the most expensive. Like I said, it was literally worth more than gold.
The colour held onto its reputation even as new methods of producing purple dye were discovered. In Tudor England, there were still specific rules over who was legally allowed to wear it. And it took until 1856 for a Victorian chemist to finally, accidentally, come up with a synthetic purple dye while trying to make an anti-malarial.
So - a fiery orange whelk laying pink eggs, inextricably tied to centuries of the colour purple.
All of which admittedly still doesn’t explain why these eggs are pink or these whelks are orange. And we can answer that question in a word, but it’s also more interesting than that.
The word is ‘carotenoids’ - a kind of pigment that shows up in a lot of animals. For example those barnacles that dog whelks are so fond of eating are chock full of it.
And carotenoids can produce a range of tones - like orange. So a dog whelk on an early diet of mostly barnacles winds up looking like this. As they age, a more varied diet and shell thickening can dull the colour to grey, brown, white or - rarely - purple.
So does this explain the eggs too? Yes and no. The pink colour certainly comes from the high carotenoid content - whelks that are already high in carotenoids will lay eggs that are too. But there may be more to it.
Think back to the environment these particular eggs are stuck in. The one which, twice a day, exposes them to air, wind, heat, direct, beating sun - and damaging UV radiation. But carotenoid pigments have some really handy properties for that environment. They are natural UV protection and antioxidants.
Just like not all dog whelks are orange, not all dog whelk eggs are pink. But it could be that the ones that are have a serious advantage. To stretch a metaphor, in the kingdom of the Fundy tidal flats, that exclusive colour… might just make them royalty.