When we think of sharks, we usually think of great whites, speedy makos, and the sleek blue shark. These popular Shark Week stars, with their streamlined bodies and blueish-grey hues, are built for speed and stealth in open waters. But let’s dive deeper. Far beneath the surface, in the depths of the ocean, live sharks that few have seen and even fewer understand.
Sharks are masters of adaptation, perfectly designed for their environments. Near the surface, our well-known pelagic sharks dominate with their swiftness and agility. Yet, these well-known sharks only scratch the surface of the diverse shark kingdom. To truly appreciate the diversity of sharkdom, we must journey into the abyss, where some ancient and mysterious species thrive.
The Greenland Shark
Take the Greenland shark for instance. This marine giant can live over 500 years, making it the longest-living vertebrate on Earth. Growing slowly to lengths of up to 24 feet, these sharks inhabit the cold, deep waters of the North Atlantic and Arctic Oceans, often found at depths of around 7,200 feet. Their flesh contains trimethylamine oxide, a toxin that can cause symptoms akin to drunkenness, leading native Greenlanders to call a drunken state “shark-sick.”
Greenland sharks aren’t aggressive hunters; they’re opportunistic scavengers, often dining on sunken whale carcasses and other carrion. Their leisurely metabolism and minimal energy requirements are ideal adaptations for surviving in the nutrient-deprived depths of the ocean. Despite their impressive longevity, much about their life remains a mystery due to the difficulty of studying them in such harsh environments. Recent technological advances, however, are beginning to shed light on these ancient mariners, offering glimpses into their biology and ecology that were once out of reach.
The Goblin Shark
Then there’s the goblin shark, a living fossil with a face only a mother could love dating back 125 million years. With its long, flat snout and protruding jaws filled with needle-like teeth, it’s a sight to behold. Found at depths of up to 4,265 feet, the goblin shark’s flabby body and large liver keep it buoyant. These slow swimmers are ambush predators, feeding on squid and fish with jaws that can extend outward to catch unsuspecting prey.
Goblin sharks are most commonly found in the waters around Japan, where they were first discovered. Their pinkish-gray coloration and unique features make them one of the most distinctive deep-sea creatures. Their specialized jaws are attached to ligaments that allow them to spring forward, enabling the goblin shark to snatch prey with lightning speed. This unique adaptation compensates for their relatively slow swimming speed and showcases the incredible diversity of evolutionary strategies in the deep sea.
The Frilled Shark
The frilled shark has remained largely unchanged for 80 million years. Named for the frilled appearance of their gill slits, these eel-like sharks grow up to 6.6 feet long and loiter at depths of up to 5,150 feet. Their hunting method is straightforward: they lunge at prey and swallow it whole using their 300 prong-pointed teeth to guarantee nothing escapes.
The frilled shark’s elongated, serpentine body is tailored for efficient navigation in the deep-sea environment. Its dark brown or gray coloration provides excellent camouflage in the low-light conditions of its habitat. Its teeth are particularly effective for catching cephalopods, a primary component of its diet. Despite its ancient lineage, the frilled shark remains one of the lesser-known deep-sea species, its mysterious life still largely hidden in the ocean’s depths.
The Cookie-Cutter Shark
The small cookie-cutter shark packs the punch of Glass Joe to its food sources, but still manages to get a good meal. Measuring just 16 to 22 inches, it attaches to larger animals with suction cup lips and carves out chunks of flesh, leaving cookie-shaped wounds. During the day, they inhabit depths of up to 12,100 feet and migrate to shallower waters at night to feed, targeting everything from fish to whales.
Cookie-cutter sharks possess a unique adaptation that makes them particularly effective at feeding. They have specialized lower teeth that are sharp and serrated, allowing them to cut out neat, circular chunks of flesh from their prey. This feeding strategy minimizes energy expenditure and maximizes the nutritional gain from each bite.
Their bioluminescent bellies help them blend into the faint light from above, making them less visible to potential predators and prey. Also, the shark’s migratory behavior, known as diel vertical migration, is driven by the need to find food and avoid predators, highlighting the dynamic nature of the deep-sea environment.
The Megamouth Shark
The megamouth shark is a relatively recent discovery, first identified in 1976. Growing up to 18 feet long, it filters plankton from the water with its massive mouth, moving to the surface at night to feed. Despite their size, fewer than 100 have been spotted since their find, making them one of the ocean’s most elusive giants.
Megamouth sharks are characterized by their large, rounded snouts and broad heads. Their distinctive mouths, which can open wide to capture large volumes of water, contain numerous small, hook-shaped teeth that help filter plankton. Although large, megamouth sharks are harmless to humans, earning them the title of gentle giants. They have a slow, graceful swimming style, which is well-suited to their plankton-feeding lifestyle. Due to their deep-sea habitat and elusive nature, megamouth sharks are rarely seen by humans.
The Bluntnose Sixgill Shark
Primitive and large, the bluntnose sixgill shark can measure up to 20 feet and has six pairs of gill slits instead of the usual five. They migrate vertically, coming closer to the surface at night to feed on a varied diet, including other sharks and crustaceans.
Bluntnose sixgill sharks are often referred to as “living fossils” due to their primitive features and ancient lineage. Their robust bodies and broad heads give them a distinctive appearance. These sharks are found in temperate and tropical seas, often near the ocean floor. Their vertical migration behavior is driven by their need to feed on prey found at shallower depths during the night. During the day, they retreat to deeper waters to avoid predators and conserve energy, demonstrating the dynamic nature of the deep-sea environment.
The Swell Shark
Smaller but no less fascinating, the adorable swell shark has a unique defense mechanism. When threatened, it swallows water to puff up, deterring predators. Found in rocky crevices of the Pacific Ocean at depths of up to 1,500 feet, they also display biofluorescence, possibly for communication.
Swell sharks have a distinctive appearance, with mottled brown and yellow skin that helps them blend into their rocky surroundings. Their ability to swell up is twofold. It not only deters predators but also makes them difficult to dislodge from crevices. This adaptation is particularly effective against larger predators that might try to extract them from their hiding spots. The biofluorescence of swell sharks is a relatively recent discovery, shedding light on the complex communication strategies used by deep-sea animals. Researchers believe these sharks may use their green light to deter competitors or attract potential mates, highlighting the importance of light in the dark depths of the ocean.
The Portuguese Dogfish
Like the cookie-cutter, the Portuguese dogfish also hang around depths of over 12,000 feet. These small, dark brown sharks feed on cephalopods and bony fish, adapting to life on the ocean floor with round, flattened snouts and small spines in front of their dorsal fins.
Their small size and dark coloration help them remain inconspicuous in the low-light environment. Portuguese dogfish are sometimes caught as bycatch in deep-sea fisheries despite their remote habitat, allowing researchers to study their biology and behavior more closely.
The Ninja Lanternshark
The ninja lanternshark, discovered in 2010, is a shark that most likely has the coolest name of any marine species. It inhabits the waters off Central America, and its jet-black coloration and bioluminescent organs make it nearly invisible in its deep-sea habitat, where it feeds on small fish and invertebrates.
The ninja lanternshark’s bioluminescence serves multiple purposes. It provides camouflage by counter-illuminating the shark’s silhouette, making it less visible from below. Additionally, the glowing patterns may play a role in communication and mating, helping individuals locate each other in the dark depths. This adaptation showcases the complexity of deep-sea survival strategies. Given its recent discovery and elusive nature (as ninjas are), much remains unknown about their feeding habits and life history. However, like other lanternsharks, it is likely to feed on small fish and invertebrates.
The Kitefish Shark
One of the largest luminous vertebrates, the kitefin shark, can grow up to six feet long. Found in deep waters worldwide, it emits light from its body to camouflage itself in the dark depths, making it harder for predators to spot it from below. Kitefin sharks inhabit depths of up to 5,900 feet, where they prey on various fish, cephalopods, and crustaceans. Like others with the ability, their bioluminescence serves both as a defense mechanism and a means to attract prey.
Kitefin sharks have a robust body and a large liver, helping them maintain buoyancy in deep water. The light-producing organs, called photophores, are distributed along the shark’s underside, creating a faint glow that mimics the light filtering down from the surface. This adaptation is particularly effective in the mesopelagic zone, where light levels are low.
The Demon Catshark
Last, but not least, the newly discovered demon catsharks inhabit the Northeast Atlantic at depths of up to 7,000 feet. With flat heads and gleaming eyes, these small, slow-moving sharks feed primarily on small fish, squid, and crustaceans.
These cooly-named sharks are well-adapted to the deep-sea environment. Their flattened body shape allows them to rest on the ocean floor, and their small, spineless dorsal fins help them navigate the complex terrain of the deep-sea habitat. Despite their widespread distribution, little is known about demon catsharks’ life history and behavior due to the difficulty of studying them in their deep-sea layer. Ongoing research and technological advancements are vital for revealing further information about these mysterious creatures and their impact on the marine ecosystem.
These sharks are just a taste of what the deep sea has to offer. The blackness regions are home to some of the most extraordinary and mysterious shark species. These creatures, with their incredible adaptations, offer a glimpse into the ocean’s twilight zones’ evolutionary history and ecological complexity. Each species is proof of the fascinating animals that lie beneath the waves, waiting to be discovered and understood.
