The frilled shark (Chlamydoselachus anguineus) is an ancient species, often referred to as a living fossil, due to its primitive physical characteristics that have remained largely unchanged for millions of years. Its bizarre, eel-like body and lizard-like head, framed by six pairs of frilly gill slits, make it one of the ocean’s most unusual inhabitants. Dwelling primarily in the deep ocean layers of the continental slopes, observations of its natural behavior are exceedingly rare. Consequently, much of what is known about its diet and predatory tactics is inferred from its unique anatomy and analysis of stomach contents.
Primary Prey Items
Analysis of the frilled shark’s stomach contents reveals that its diet is heavily dominated by cephalopods, specifically deep-water squid. In regions like Japan’s Suruga Bay, squid can account for approximately 60% of the food items found in its digestive tract. The frequent presence of hard squid beak remnants confirms their importance as a primary food source.
The species preys on a range of squid, including both slower-moving, deep-dwelling types and faster, open-ocean swimmers such as those in the Onychoteuthis and Todarodes genera. Beyond cephalopods, the frilled shark also consumes smaller bony fishes found in the deep sea. Occasional findings show that the shark preys upon other small sharks, indicating an opportunistic predatory nature. For example, one notable specimen was found to have swallowed an entire Japanese catshark, which weighed over a pound.
Hunting and Capture Strategies
The frilled shark’s specialized physical structure is adapted for capturing soft-bodied and slippery prey in a rapid, ambush-style strike. Unlike most modern sharks, its long jaws are attached directly to the cranium, allowing for a remarkably wide gape. This jaw articulation enables the shark to engulf prey that can be up to half its own length, sometimes even exceeding its own size.
Its mouth contains approximately 300 teeth arranged in about 25 rows, but these teeth are not designed for cutting or tearing. Instead, each tooth is small, needle-sharp, and trident-shaped with three recurved, inwardly-pointing cusps. This configuration acts like thousands of tiny fish hooks, creating a highly effective trap for gripping and holding onto struggling, slick prey like squid or other sharks.
The shark’s long, flexible, eel-like body is believed to be used in an anguilliform lunging maneuver. This movement allows it to coil and then quickly straighten, striking out to engulf its target with a rapid bite. The shark may also use its unique anatomy to create a suction effect, rapidly closing its gill slits to draw water and prey into its gaping mouth.
Deep-Sea Feeding Environment
The frilled shark’s habitat on the outer continental shelves and upper slopes, typically between 500 and 1,500 meters, is characterized by low energy and scarce food resources. This environment dictates an opportunistic feeding strategy and a slow metabolism, which permits the shark to survive long periods between meals. The necessity of maximizing caloric intake from infrequent encounters explains the adaptation to swallow large prey whole, rather than processing it into smaller pieces.
To access a greater variety of prey, the frilled shark participates in diel vertical migration. This involves moving up from its deeper daytime resting depth to shallower waters, sometimes as high as 50 to 200 meters, during the night. By migrating, the shark can intercept faster-swimming organisms that also travel up the water column. The ability to catch both slow-moving benthic animals and pelagic species demonstrates the flexibility required to survive in the deep ocean.