What is the side line?

The side line is a slightly visible line of dots that runs down the sides of most fish, from the area around the gills to the tail. It is often clearly visible, but it looks like nothing but a cosmetic feature that serves no purpose. In fact, it is a sensory organ with microscopic structures below the surface of fish scales and serves as a primary method for detecting changes in water pressure.

Sensory organs on aquatic species may often be difficult to identify, but since the side lines are present in so many fish species, as with juvenile amphibians, it has been studied quite extensively. There is a gel closure under each dot on the line and the structure itself is called neuromast. Neuromast is a sensory cell focused on nerves. The gel detects changes in the surrounding water and transmits this sense to small hair that activates nervous tissue in a similar way as the human inner ear works.

Fish nervous system can be very accurate when considering the side line, to the extent that the fish can feel a smalla change in water pressure as it changes the direction in the water or as other fish or objects approach. This allows the fish to swim in the dark and in schools of other fish and maintain an established distance from these objects. The sensory organs, such as the side line, also give fish the ability to perceive the movement near the back of their bodies, while their eyes are fixed in general forward and direction. This helps to avoid predators and also in search of food sources such as insects on the water surface.

Sharks also have a side line and use it to detect vibrations and odors in water in a process known as whirlpool chemotaxes. This is well served by the type of predators, because most of the prey of animals such as seals when they swim across the ocean. The side lines rely so much on sharks and fish, which are considered almost as important as a sense of sight. Shark -common behavior often involves impact or friction against unknown animals in the sea, such as human divers. This is theorized as a method for a shark tastingBy bringing it into contact with the side line directly to see if it is safe to eat.