The Strange Case of Vanishing Organs
Unlike humans, whose organs grow and change throughout life, baby octopuses develop temporary structures that disappear entirely. These microscopic features, called Kölliker’s organs (KO), appear before birth and cover the embryo’s body. Hidden within small skin pockets, they can evert like tiny umbrellas, displaying bristly fibers that resemble brooms or dandelion flowers.
Decades of Mystery
Scientists have long known about KO, but their purpose remained unclear. Octopuses lose these structures before adulthood, leaving researchers puzzled. A recent study led by Roger Villanueva at the Institut de Ciències del Mar, published in Frontiers in Marine Science in May 2021, offers new clues by examining 17 octopus species with light-sheet microscopy. This imaging technique immerses samples in fluid, making them transparent and easier to study under light.
What the Research Revealed
- Of 17 species studied, 15 had KO. The two that did not were holobenthic octopuses, born large and dwelling in the deep sea.
- Most species with KO were planktonic, born tiny and floating near the ocean surface.
- KO are evenly spread across the embryo’s body and remain the same size regardless of the embryo’s overall size.
- When fully extended, KO increase a young octopus’s surface area by about two-thirds.
Possible Explanations
One theory suggests KO help young octopuses adjust their surface-to-volume ratio, improving their ability to move with or against ocean currents. This adaptability could help conserve energy during their vulnerable planktonic stage. Another possibility is camouflage. A 1974 study showed KO can refract light in multiple directions, potentially blurring the hatchling’s outline and hiding it from predators. For deep-sea species living in darkness, camouflage would be unnecessary—possibly explaining why some do not develop KO at all.
A Mystery Still Unsolved
Despite these insights, the ultimate purpose of KO remains uncertain. Researchers emphasize that more observations of hatchling octopuses in their natural habitats are needed. For now, KO stand as a reminder of the ocean’s mysteries, balancing between function and beauty.
The Beauty of Discovery
For scientists like Montserrat Coll-Llado, a mesoscopic imaging specialist at the European Molecular Biology Laboratory, studying KO has been a breathtaking experience. She likened exploring the intricate tissues of hatchling octopuses to wandering through undiscovered corners of a city—except far more wondrous. These fleeting organs, though temporary, reveal the remarkable complexity of octopus life and the endless possibilities of marine biology research.
