The Ears

Crabs don’t really have ears, but crabs do make noises.

In previous posts we’ve written about how the Atlantic Ghost Crab grinds its gut to emit sound. The Sand Bubbler crab also brushes the joints of its legs against its shell to make a noise. So it seems only right that they have a way of hearing too.

Instead of ears like us, they make use of thousands of microscopic hairs all over their bodies to sense their environment.

These hairs are called setae, and they can detect changes in water pressure, which is translated into signals to their central nervous system.

It has been found that hearing plays an important role in how crabs live. Reefs are the ideal habitat for many species of crab and they are noisy places.

In a study by Stephen Simpson of the University of Bristol, fish and coral larvae were attracted to the simulated noise of reefs.

Crab larvae however, being a little bit more selective, were only found in greater numbers if they were a species that lives in a reef environment. Open sea crab species were not attracted to the simulated sound of the habitat.

The science behind crab hearing has come a long way in past years. The 1965 book ‘Crustaceans’ by Waldo Schmitt was uncertain about how crabs process sound, he writes:

“The fact that many investigators have failed to find any sense of perception that might be called auditory in Crustacea is no proof that these animals do not appreciate sound and sound vibrations… It may be that both in our reasoning and our experimental investigations we fail to “speak their language”.

Of course, today we are not much closer to understanding their language. For example, whether they prefer their eggs poached or fried, but perhaps the future of science will change all of that!