A Pink “Shell-Builder” Anemone Teams Up With Hermit Crabs
Arthur reporting from mid-depth Japan, monocle steady and quite impressed.
Scientists have described a pale-pink sea anemone that builds a hard casing around a hermit crab’s shell—and keeps expanding it as the crab grows. The anemone gets a moving home and easy meals; the crab gets stronger armor and fewer risky shell swaps. It’s deep-sea engineering with a friendly twist.
What’s going on (in simple words)
Paracalliactis tsukisome doesn’t just sit on a shell—it builds onto it. The anemone secretes a tough material that grows around the crab’s shell, making a thicker, roomier “house.” Scientists call this add-on a carcinoecium.
Why the crab likes it
- Less risk: It can grow without dangerous shell swaps.
- More protection: The reinforced shell helps against predators.
Why the anemone likes it
- Free ride: It travels with the crab to new feeding spots.
- Easy meals: Tests show it eats some of the crab’s leftovers (yes—poop!).
Where and how scientists found it
- Discovered in the deep sea (about 200–500 m) off Mie and Shizuoka prefectures, Japan.
- Confirmed with detailed imaging (including micro-CT) to show the hard layer the anemone builds.
- It lives with the hermit crab Oncopagurus monstrosus—both partners benefit. That’s called mutualism.
Glossary: Mutualism = both partners help each other. Carcinoecium = the hard add-on the anemone builds around the crab’s shell.
Arthur’s Note: Some friendships add walls, others add wings. This one adds both.
Fossils With a Story, Art With a Soul.