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Crustaceans have teeth in their stomach

Lobsters and crabs have teeth— in their stomachs. These are used to crush its food, but they also have a strange secondary function in ghost crabs: making a noise that wards off predators.

Believe it or not, lobsters, as well as other crustaceans such as crabs and crayfish, have teeth in their stomach! The teeth are part of a system called the “gastric mill.” Through rhythmic movements of these large teeth, of which there are three, their stomachs can actually crush food as a prelude to further digestion.

Ghost crabs use their “stomach teeth” in a secondary fashion as well. It sounds strange, but these crabs actually use the gastric mill to generate noises that ward off predators. Essentially, by grinding the teeth in their stomach, much like they would do to break up food, the ghost crabs can produce sounds resembling that made by rubbing the ridges on their claws together. This noise is often made by the crabs when they feel threatened and is thought to act as a warning sign to scare predators away for fear of being clawed. The sound may also be used to communicate information about a crab’s size, aggression, and intent.

Ghost crabs’ ability to produce this sound with both their claws and their stomach, gives them a “double-edged sword” when it comes to engaging in battle. Even with their claws engaged in fighting, they can still grind out warning signals with their “stomach teeth.”

Caitlin Bard is completing her Bachelor of Science with a major in neuroscience at McGill University.

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