If you’ve ever seen a picture of a shark, you will notice that they are missing an important body feature that most animals have – ears!
Does this mean that sharks can’t hear, or does their hearing system work completely different from ours?
Here, we are going to talk about sharks and their hearing systems so you can learn everything you need to know about how sharks hear underwater.
Do Sharks Have Ears?
Despite appearances, sharks actually do have ears – it’s just that they are internal rather than external.
This means that you can’t see their ears like we can see the ears of humans or elephants. Instead, sharks keep their ears hidden underneath their skin which makes them invisible to our eyes.
The only sign of a shark’s ‘ear’ on their bodies is a very thin opening on either side of their head. This leads to their inner ears which are found embedded in the shark’s frontal skull.
The opening for the ear is found behind the shark’s eyes and is actually very close to the spiracle, another opening which helps with the respiratory system of a shark.
Many people mix these two openings up but typically, the ear is found behind the spiracle (this can change depending on species).
So, sharks do indeed have ears but they are internal rather than external – but can they still allow hearing like our ears do?
Do Sharks Hear?
The shark’s internal ear plays an important role in hearing even though their ears are built very differently from ours.
Their ears are filled with ducts and sacs that are filled with endolymph – a clear fluid is mainly made of seawater that fills the ducts of a sharks’ ear.
This whole system is protected by a lot of cartilage, sustaining the canals that lead to the sacculus and lagena.
The acculus is made from otoliths, which are small particles which are made from calcium carbonate and gelatinous matrix.
Attached to the otoliths are sensory hairs known as cilia. There is a longer hair cell known as the kinocilium which stretches up into the cupola, which is partly exposed externally.
Sound vibrations that travel through the water makes the jelly-like cupola wobble and this transmits the vibrations through the kinocilium to the brain.
There are also three tubes of cartilage within the ear that each lies at different angles to one another. When one tube vibrates, the shark can sense which direction the vibrations (and thus movement) is coming from.
As a result, the shark can hear!
But the shark’s ears are not just used for hearing. They help the shark maintain its balance and equilibrium so it can swim with ease.
Whenever a shark is thrown off balance, the endolymph fluid and otoliths slow so help the cells detect any lag, thus sending the correct signals needed for the shark to right itself.
So, the shark’s ears function in a very similar way to ours by helping with balance and hearing, but are built very differently and thus, more adept at hearing over long distances and underwater.
So, sharks can hear just like a lot of other animals even though the way their hearing works is very different from ours.
Sharks rely on vibrations in order to sense movement elsewhere and thus, their ears are built very differently from ours.
Not only do they contain a lot more seawater, but they are also stored internally with different components that help the shark sense vibrations in different directions.
Their ears are also important to help them stay balanced so they can swim in different directions towards (or away) from the movement. This allows them to use hearing alongside their sharp noses to find prey.
So, despite appearances, sharks have very acute hearing which allows them to find and hunt prey underwater!