The Frilled Shark: Ancient Predator That Survived the Dinosaurs

In the deep ocean, where food is scarce and the environment is harsh, the frilled shark has survived by abandoning the typical predatory path of speed and power. While other sharks evolved into fast pursuit hunters, this species focused on energy conservation, a strategy that has allowed it to persist for roughly 150 million years.

The shark resembles a cross between an eel and a snake, reaching up to two meters in length. Its most striking feature is the series of skin folds around the gill slits, which form a collar or "frill" that fluctuates in the current. This anatomy makes it a biological rarity, as its skeletal structure and gill arrangement remain largely unchanged since the Mesozoic era.

The feeding mechanism of the frilled shark is specialized for the deep-sea environment. Its jaws are lined with up to 300 trident-shaped teeth. These teeth are angled inward, acting as a one-way trap; once a slippery prey item enters the mouth, the inward-pointing crowns prevent it from escaping. According to Mikhail Kravtsov, a pet care specialist, this structure ensures that prey is locked in place immediately upon contact.

To survive in the abyss—typically at depths exceeding 1,200 meters in the Pacific and Atlantic oceans—the frilled shark minimizes metabolic costs. Unlike active hunters that rely on heavy muscle mass, it possesses a massive, oil-rich liver. This organ provides neutral buoyancy, allowing the shark to hover in the water column with minimal effort.

Maxim Lavazev, a veterinary physician, explains that this hepatic buoyancy is a critical adaptation for the deep sea. By reducing the need for constant swimming to stay afloat, the shark conserves energy in a region where food sources are sporadic and unpredictable.

The shark's hunting behavior changes with the light cycle. At night, it ascends to shallower waters to hunt squid, small fish, and occasionally other sharks. It employs two distinct methods of capture:

• Suction feeding: By rapidly expanding its mouth and compressing its gill folds, the shark creates a zone of low pressure, effectively vacuuming nearby prey into its maw.
• The strike: For larger prey, the shark remains motionless, detecting vibrations via its lateral line, before launching a sudden, snake-like forward strike.

The elasticity of the stomach and jaw allows the frilled shark to consume prey up to half its own body length. Pavel Smirnov, an animal behavior expert, notes that this ability is a common trait among deep-sea predators, ensuring that a single successful hunt can sustain the animal for a long period.

The species' reproductive cycle is one of the slowest among vertebrates. Gestation can last up to 3.5 years, during which the embryos depend entirely on a large yolk sac for nutrition. A single litter consists of 2 to 15 pups, each roughly 60 centimeters long. It takes approximately 10 years for an individual to reach sexual maturity, and the total lifespan is estimated at around 25 years. This slow rate of reproduction makes the population sensitive to environmental shifts, though the species is not currently classified as endangered.

Due to its habitat and behavior, the frilled shark poses no risk to humans. Most scientific data on the species is gathered through accidental catches by deep-sea trawlers or rare footage from remotely operated vehicles (ROVs).