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Galatheid crab. Credit: Tamara Frank, National Oceanic and Atmospheric Administration
You can find creatures on the bottom of the ocean that’ll eat just about anything — from the poop of other organisms to minerals that bubble up from below the ocean floor. Even so, the diet of one type of crustacean is a bit of a surprise. That’s because it feeds on something you wouldn’t expect to find on the ocean floor: wood.
This creature is known as a galatheid crab or a squat lobster. It has relatives all over the planet. Many of them are scavengers that eat whatever they can find. But a few years ago, marine biologists discovered that members of one species — Munidopsis andamanica — appear to have a specialized diet. They eat mainly wood and a thin film of microscopic organisms on the surface of the wood.
The species is found around several island chains in the Pacific Ocean, at depths of hundreds or thousands of feet. The crabs are tiny — only a couple of inches long. They congregate around trees that were swept out to sea, or around the hulls of sunken ships.
They probably bite off small bits of wood, then use a series of strong teeth to grind it down. Colonies of bacteria and fungi in their stomachs produce enzymes that break down cellulose — the chains of sugar molecules that make up the wood.
These crabs aren’t the only creatures to take advantage of fallen trees and boats — so do many worms, other crustaceans, and other forms of life. They confirm that you can find a critter that’ll eat just about anything on the ocean floor — no matter where it came from.
