What is a shark’s lateral line?


By Blaise Jones

Sharks have a plethora of senses that allow them to maintain their mastery of the oceans. Their eyes, ears, and noses are amazingly adapted to their environments, allowing them to see, hear, and smell, respectively, almost anything in their environments. However, sharks aren’t limited to just five senses, like humans. Sharks possess body parts that give them abilities other animals, like humans, do not possess such as the lateral line.

A Series of Tubes
As its name implies, the lateral line runs down the side of the animal. The lateral line starts as a series of pores that connect the water outside the shark’s body to a channel that runs beneath its skin. This is the actual line. The line itself is filled with a gel-like substance and millions of sensory cilia attached to nerve endings that transmit the sensory data gathered by the lateral line directly to the shark’s brain. But what exactly is this sensory data that’s collected?

Good Vibrations
The purpose of the lateral line is to detect vibrations in the water, which can provide a wealth of information to the shark even in complete darkness. The ocean is an amazing conductor of vibrations and sound waves that are transferred as ripples of water pressure and are affected by differences in temperature and water density. Sound can actually bounce between these temperature and density differences, allowing for the pressure waves to travel for miles.

The ears and lateral line of a shark can detect the slightest difference in the water caused by these echoing pressure waves.

More than a Feeling
However, despite sharing similar functions and even using the same type of sensory cilia, the lateral line can do something a shark’s ears cannot. Lateral lines are able to sense the changes in pressure waves of the surrounding water in relation to the shark’s own body.

As the shark moves through its environment, countless currents brush against its skin. These very same currents and pressure waves come into contact with objects in the shark’s environment and are changed by this contact. The shark’s lateral line is able to sense these minute differences and the animals are able to “feel” the environment around them. This allows sharks that have been blinded or are swimming in dark water to know the location of every object and animal around them.

Similar to echolocation used by many animals, including the narwhal and orca, the sharks’ ability to sense its environment thanks to its lateral line is a sensory experience no human has ever experienced.

“[Like] feeling the wind on our faces and skin when we’re outside,” was the closest explanation shark expert Steve Parker used to describe the sensory ability of the lateral line. Now imagine using that feeling to navigate an obstacle course in the dark.



“The Encyclopedia of Sharks” by Steve Parker