The frilled shark (Chlamydoselachus anguineus) is an enigmatic deep-sea dweller rarely encountered by humans. This creature appears to be a relic from a distant prehistoric era, swimming deep within the ocean’s dark, cold abyssal zones. Its bizarre, snake-like appearance and preference for remote waters make its age and life cycle subjects of intense scientific curiosity. Determining the lifespan of frilled sharks is complex, requiring scientists to piece together clues from its ancient biology and extreme habitat.
The Ancient Lineage
The frilled shark is often described as a “living fossil” because its physical form has changed very little over millions of years. Its lineage can be traced back to the Cretaceous period, over 95 million years ago, representing one of the oldest surviving shark groups.
Its body is long and slender, resembling an eel or a sea serpent, reflected in its species name, anguineus. It possesses six pairs of gill slits, unlike the five found in most modern sharks. The first pair nearly meets across its throat, creating a fringed or “frilled” margin that gives the animal its common name.
The frilled shark’s head is flattened, and its jaws are positioned at the end of its snout, a trait considered ancestral among sharks. Its mouth is lined with roughly 300 needle-sharp, trident-shaped teeth, each featuring three backward-curving cusps. This specialized dentition is suited for grasping and impaling the slippery cephalopods and fish that make up its diet.
Determining Frilled Shark Lifespan
Directly determining the age of a frilled shark presents a significant challenge due to its deep-water habitat and the rarity of specimens. For most shark species, age is estimated by counting the growth rings deposited on their vertebrae, similar to counting annual rings on a tree trunk.
The frilled shark’s soft, poorly calcified skeletal structure makes interpreting these vertebral growth rings particularly difficult. Scientists must rely on specimens caught accidentally as bycatch in deep-sea fishing operations. Furthermore, the growth rate of deep-sea species is often nonlinear, meaning the rings are not always deposited on a predictable annual schedule.
Despite these hurdles, scientific analysis suggests a remarkably long lifespan for the species. The slow metabolic rate resulting from its cold, nutrient-scarce environment indicates extended longevity. Based on these factors, the estimated maximum lifespan for the frilled shark is thought to be around 25 years.
Deep-Sea Habitat and Reproductive Strategy
The frilled shark primarily inhabits the outer continental shelves and upper continental slopes, typically living at depths between 500 and 1,000 meters. This bathypelagic zone is characterized by extremely cold temperatures and low food availability, which directly influences the shark’s biology.
The species exhibits a unique reproductive strategy known as aplacental viviparity, where the embryos develop inside the female’s uterus, nourished only by a yolk sac. This method, combined with its deep-sea adaptation, results in an exceptionally protracted gestation period.
Estimates indicate that the female frilled shark may be pregnant for up to 3.5 years, currently considered the longest gestation period of any known vertebrate. During this extended pregnancy, the embryos grow very slowly, perhaps at a rate of only about 1.4 centimeters per month. This delayed reproduction contributes significantly to the species’ vulnerability, as the population recovers slowly from external pressures like accidental capture.