Above us, as we walk the untouched sands of Barley Cove on the Mizen Peninsula in Cork, a ribbon of milky-white clouds folds and ripples through the transparent, pale-blue sky as the sun’s rays, powerful for so early in the year, bounce off the water below. Spending a few days away with family and friends, it feels fortunate to have the place to ourselves.
An ivory-coloured, crescent-shaped object, just under the length of a ruler, catches our attention. We notice more of them scattered haphazardly across the sand, lying like elongated fragments of ivory; some whole, like crescent moons, while others are jagged and broken, like pieces of a broken puzzle.
They’re cuttlebones from cuttlefish. Lightweight, firm, yet brittle, they are the internal shell that runs the length of the body. Each is the remnant of a single cuttlefish, which typically dies soon after spawning in late winter or early spring, depending on the water temperatures. Warmer waters will stimulate early breeding activity, maybe a clue to why so many are here. Or perhaps it’s just the thunderous aftermath of Storm Éowyn.
Within a few steps, my son and I collect four cuttlebones. Despite their name, cuttlefish aren’t fish; they belong to the mollusc group, like snails, but are more closely related to octopuses and squids. Over 600 million years ago, soft-bodied molluscs with simple external shells evolved to grow chambers in the shells which could be gas filled, which meant they could control their buoyancy in the water without constantly swimming. This internal shell in the cuttlefish is known as the cuttlebone.
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Standing on the beach, I snap one in half. The cuttlebone is hard, but the internal structure is fragile, revealing a honeycombed network of tiny chambers arranged in a grid-like pattern. The material is porous calcium carbonate and, by adjusting the gas pressure – carbon dioxide and nitrogen – within these chambers, the cuttlefish can effortlessly control its depth in the water, allowing them to hover in water. When the chambers are filled with gas, the animal floats upwards.
With a life designed for high energy, cuttlefish could adopt the motto “Live fast and die young”. They’re known for their short lifespan and are lucky if they make it to 24 months. Once born, they feed voraciously to fuel their bodies, growing astonishingly fast; within a few months, tiny, one-inch hatchlings transform into fully mature adults, as long as a standard loaf of bread. They breed only once before dying.
The fossil record of cuttlefish ancestors goes back hundreds of millions of years, and they’ve survived repeated mass extinction events. They’re a species able to push through and adapt quickly in the face of dramatic environmental changes. With brains nearly as complex as a dog – some scientists suggest even a young human – they can react to new challenges. They can even work out how to exit a maze.
I look at a photo online of a common cuttlefish in the water. Its appearance is unusual, almost weird – it wouldn’t look out of place as a magical creature in Harry Potter. From a bulbous head, two dark, orb-like eyes bulge out. In darkness, their pupils are circular but, in bright light, they switch to a distinctive wavy shape, which is thought to aid vision and camouflage. Eight arms extend from their head into the water. The mouth, curved downward, resembles a parrot’s beak. The main body, the mantle, houses the cuttlebone and vital organs and wraps around the cuttlefish like a protective cloak, allowing for graceful movements through the water.
When cuttlefish contract their mantle, they increase internal pressure, forcing water through their siphons in various directions. This generates thrust, enabling jet-like movements in multiple directions to escape predators. Inspired by this natural mechanism, medical engineers have designed high-velocity microjets for humans which self-propel to deliver drugs through the skin without needles, minimising damage to human tissue, such as that found in the gastrointestinal tract.
By releasing melanin-rich ink, cuttlefish can create a smokescreen to confuse predators and escape. Last month, scientists from University College Dublin published a new study suggesting that cuttlefish ink overwhelms a predatory shark’s sense of smell, causing it to avoid areas where the ink has been dispersed.
Sensory biologist Colleen Lawless, one of the study’s authors, tells me that sharks are deterred by the smell of cuttlefish ink in the water – it’s like walking out of a room smelling of flatulence, she explains – prompting them to immediately swim away.
In regions where swimmers or surfers frequently encounter sharks, this discovery could inspire the development of artificial chemical compounds that mimic cuttlefish ink’s structure and function, offering a non-invasive and non-damaging way to keep sharks at bay.
From medical implements to dealing with sharks, cuttlefish continue to inspire and help us solve our problems. In death, being boneless, the only trace they leave behind is their pearly white, curvaceous cuttlebone. On Barley Cove, we gather eight of them in our arms and bring them home.
