These Incredible Abilities Give Sharks A Sixth (And Seventh) Sense
When most people hear the word “shark,” it conjures up images of the ravenous great white menace from Steven Spielberg’s 1975 classic film Jaws - an unstoppable killing machine bent on gobbling up unsuspecting skinny dippers. The conventional image of the shark is the fearsome, omnivorous hunter with a murderous, tooth-filled maw that spells doom for all who encounter it. This has led to an often irrational fear of what is actually a remarkable and misunderstood animal. But really, sharks are awesome creatures with incredible power, and once you read some incredible facts about sharks, you might think twice about how scary they are.
Sometimes shark behavior is so eerily prescient it’s enough to make one believe in shark premonitions. Due to common myths and misconceptions about amazing shark abilities, it has superstitiously been assumed that sharks have a supernatural sixth sense. While the reasoning might have been somewhat flawed, the conclusion is closer to correct than one might think. So, do sharks have a sixth and seventh sense that has kept them near the pinnacle of the aquatic food chain for millions of years running? And if they do… how do they work?
What Are Sharks?Photo: Terry Goss / Wikimedia Commons / CC-BY-SA 3.0
Sharks are part of a unique and distinct sub group of fish known as elasmobranchii of the group Chondrichthyes, commonly identified by the fact they have no actual bones. The framework of a shark is composed of calcified cartilage. This trait is shared only amongst a small number of sea creatures, most notably the shark's closest relative, the ray. But that's only where the differences that set sharks apart as a species begin. Evolution and adaptation has declared the shark an apex predator, and it’s been holding the title for over 16 million years. In truth, sharks share all the same senses humans do, but that’s just for starters.
The Ampullae Of Lorenzini – A Verifiable Sixth Sense That Lets Them Target Their PreyPhoto: Pexels / Pixabay / Pixabay License
The ampullae of Lorenzini are special sensing organs - sometimes called electroreceptors - that form a collection of jelly-filled pores. They're named after Stefano Lorenzini, an anatomist believed to have first observed congregations of pores around the nostrils and mouths of sharks and rays in 1763. He noted there were so many pores, they almost looked like a sort-of beard. When peeling back the layers of flesh around the pores, he saw that they were filled with a jelly-like substance.
The purpose of these pores and their mysteries eluded him throughout his life, though he clearly believed they had greater purpose than anything he was able to discern. By the 19th century, advanced microscopic technology revealed those pores and the tubes of jelly led to nerves that lay just under the skin of the shark. It took until the 1970s for researchers to understand that these nerves can actually detect electromagnetic fields generated by the muscular contraction of sea life.
Sharks may have as many as 3,000 of these very specialized nerves, which, during the final phase of their hunt, allow them to orient and target their prey with laser-like precision even in literal pitch darkness. Further, by using this remarkable, quantifiable sixth sense, sharks are able to use the electromagnetic field of the planet to navigate oceans.
The Lateral Line - Radar For SharksPhoto: Chris huh / Wikimedia Commons / Public Domain
During the 19th Century - and around the time researchers were beginning to try and understand what Lorenzini had discovered - scientists found an organ in sharks and other marine life called the lateral line. The lateral line is an array of scales that connect to small hair-like projections (cilia). When water is displaced by the movements of nearby creatures, these small brushes of fine hairs bend and sway in waves like fields of grain in a gentle breeze.
These swaying waves of cilia inform the shark’s brain of the strength and direction of the displacement. Thanks to a common ancestor from 450 years ago, humans have a descendant of the lateral line system present in the cochlear formations in our ears. Just as the lateral line helps sharks orient and hone in on targets in the directionless depths of the oceans, the cochlea of humans allow us to stand upright and retain our balance on dry land.
Pit Organs Could Be A Shark's Eighth SensePhoto: Albert kok / Wikimedia Commons / CC-BY-SA 3.0
To illustrate just how much researchers don’t understand about the amazing animal that is the shark, it should be noted while they are aware of the existence of the pit organ, marine biologists are still quite unsure what it actually does. What is known is that the pit organ consists of two denticles in the skin folds along the jaw line, sides, and backs of sharks, and that the cilia within them lead directly to sensory organs and the brain. While small, they are usually concentrated with nerves and it has been theorized that the organ allows the shark to detect changes in water pressure or temperature.
Sharks Use Tactile Sensation - The Ability To Detect Movement - To 'Feel' ThingsPhoto: Kris Mikael Krister / Wikimedia Commons / CC-BY 3.0
Tactile sensation is a remarkable process in sharks. Lacking any sort of protuberances like hands for probing, they have developed a way of feeling things that are actually pressure sensitive, allowing them to more quickly determine if the thing in their mouth should be eaten. Once again, this has helped humans in terms of surviving shark encounters, since the naturally inquisitive creatures will often take an exploratory bite of something then quickly move on once it decides it shouldn’t be swallowed. Basically, a shark can feel vibrations and detect movement, which gives them a sort of extra sight through their skin, so to speak.
Sharks Can See 360 Degrees Around And Extremely Well In The DarkPhoto: Jean-Lou Justine / Wikimedia Commons / CC-BY-SA 3.0
The structural make-up of a shark’s eye is not unlike that of a human, up to a point. With eyes composed of an iris, lens, retina, and nictitating membrane, sharks enjoy a full color and practically 360-degree field of vision.
For humans, the ability to see underwater is only applicable to a depth of approximately 50 meters, depending on other water conditions. For sharks, it’s a completely different story. While shark eyes share traits with human beings, they also demonstrate an ability most commonly associated with felines that allows them to see roughly 10 times better in the dark. The tapidum lucidum is a structure allowing sharks and other creatures that function in low light to collect and amplify any available light around them.
The crystalline photoreceptors that make this possible are what give sharks and cats (as well as deer, rodents, and a few other animals) eyes that seem to glow in the dark. For all that a shark’s eyes are an amazing weapon, they are really only useful once the shark has advanced to within a few meters of its prey.