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How the Coelacanth Works

The Coelacanth's Significance
Could this limblike fin provide a clue to the missing link between sea creatures and land animals?
Could this limblike fin provide a clue to the missing link between sea creatures and land animals?
Ronan Bourhis/AFP/Getty Images

You know those Darwin fish bumper stickers — the ones where the fish have legs to indicate man's evolution? Well, the coelacanth is potentially critical to our understanding of how creatures walked out of the sea and onto the earth. That's because it has four fins, or lobes, sticking out of its body like legs. Even more fascinating, it moves those fins in an alternating fashion that resembles walking or trotting. But coelacanths aren't predecessors of tetrapods, or four-legged animals that live on land. Thanks to an analysis of the coelacanth genome, we now know that tetrapods have more in common with lungfish. Yet even if coelacanths occupy another branch in the vertebrate family tree, they're still important to our understanding of how creatures moved from water to land. For this reason, the coelacanth's discovery is considered one of the most important zoological finds of the 20th century [source: Bates].

Besides possibly aiding in explaining the water-to-land transition, coelacanths have some remarkable aspects. First, to help them eat super-sized prey, their jaws have a special hinge that allows their mouth to open wide. They also have a notochord instead of a spine. A notochord is a hollow, pressurized tube; in coelacanths, it's filled with oil. Vertebrates usually start life with notochords, but as the embryo develops, the notochord is replaced by the spine (vertebral column). Coelacanths are also pregnant for a long time — up to three years — and they give birth to live offspring, which is unusual for fish. Finally, scientists say the fish probably use electroreception to help sniff out their next meal and avoid swimming into various aquatic obstacles [sources:, Bates].