Sharks: The Sixth Sense
Author Hunter Wortmann
Sharks have been around for more than 450 million years and have evolved into a plethora of different species with a vast array of capabilities. This amount of time has allowed them to evolve complicated sensory systems to process information and survive the unique challenges their marine environment provides. Sharks have relatively large brains and share all the senses that humans have, plus and additional sixth sense. Just like us sharks can see, smell, taste, hear and feel. However, their unique sixth sense is arguably the most crucial to their survival and long history on this planet.
Let’s dive in to the familiar five senses:
Sight
Sharks have nearly 360 degrees of vision and very sensitive eyes which aid them in finding prey and identifying predators. Some sharks like the hammerhead shark have nictating membranes which cover their eye to protect them while feeding. Sharks are thought to be colorblind and their eyes work best in dim light around dusk and dawn when they are hunting for prey.
Smell Sharks can smell underwater? Indeed, they can. Sharks have external nostrils called nares (which are separate from their respiratory system made up of the gills and mouth). Water flows over olfactory (scent) receptors in the nares which transmit scent information to their brain. Sharks use their nose to locate potential prey items as well as potential mates. It is said that shark’s noses are so sensitive that they can sense a drop of blood in a swimming pool.
Taste
Not much is known about the extent of a shark’s sense of taste. Sharks do not have tongues like humans and cannot distinguish between salty, sweet, sour and bitter. However, sharks do have the capability of determining what is and what is not their intended food. Sharks have been observed biting on potential prey items and spiting them out as it is not what they thought they were consuming.
Hearing
Sound travels four times faster in water than it does in the air which creates differences in how marine animals perceive sound. Sharks have an inner ear like humans that can perceive sound but also aid in balance and body orientation. Sharks’ inner ears are best used for perceiving low frequency sounds which include sounds made by injured fish from distances of up to 270 yards.
Touch
Sharks have a specialized sensory system called the lateral line. Sensory receptors located along the shark’s body detect the displacement of water and provide the shark more information about its surroundings. The lateral line assists sharks in detecting prey, avoiding predators, swimming in schools and identifying the topography of their surroundings.
Finally.. the Sixth Sense!
Electroreception
Electroreception in sharks allows them to detect electrical fields. Through the use of their ampullae of Lorenzini located in their snout, sharks can detect electrical fields produced by animal’s heartbeats. The ampullae of Lorenzini are small gel filled sacs that conduct electrical impulses given off by muscle contractions of animals in the environment. These electrical signals are then transmitted to the shark’s brain to aid them in locating their host. This allows sharks to sense prey items that may not otherwise be sensed through hearing, sight, smell or touch. The process of electroreception also allows sharks to navigate using local magnetic fields generated by the earth. This internal compass is a necessary tool in mass migrations of shark species.
These six senses are extremely important for the day-to-day survival of sharks and the continuation of their species. These senses have evolved for millions of years across different species of sharks. Thanks to their senses, sharks are equipped with vast capabilities that allow them to succeed in many different habitats and grant them a place at the top of the food chain.
Sources
1. The Shark Handbook by Dr. Greg Skomal