The slow-moving shark that can live for four hundred years
The Greenland shark is the longest-lived vertebrate on Earth. Living in the freezing waters of the North Atlantic, they grow at a rate of only about one centimeter per year. Marine biologists estimating their age using radiocarbon dating of eye proteins discovered that these sharks can live for four centuries, reaching sexual maturity at around one hundred and fifty years.
A Ghost in the Deep Arctic
In the near-freezing depths of the North Atlantic and Arctic Oceans, the Greenland shark (Somniosus microcephalus) drifts through waters that would kill most other large vertebrates. Belonging to the family Somniosidae, commonly referred to as sleeper sharks, this heavy-bodied species thrives in environments where water temperatures can plummet to below freezing. They inhabit a vast vertical range, often descending to depths greater than 2,000 meters, where the crushing pressure and perpetual darkness create one of the most extreme marine ecosystems on Earth.
The physical profile of the Greenland shark reflects its sluggish lifestyle. Growing to lengths comparable to the great white shark—with mature individuals frequently measuring between three and five meters, and rare specimens documented at over six meters—the species moves at a remarkably languid pace. Its typical cruising speed is barely over one kilometer per hour, propelled by a broad, heavy tail that beats once every seven seconds. This glacial movement is an adaptation to an environment defined by limited energy, sparse food, and bone-chilling cold.
Measuring Centuries in the Eye Lens
For decades, the exact lifespan of the Greenland shark remained an elusive mystery. Most sharks and bony fish are aged by counting growth rings in calcified structures such as vertebrae or otoliths. The Greenland shark, however, is a cartilaginous fish with an exceptionally soft skeleton that lacks rigid, calcified deposits, leaving researchers without standard anatomical rings to tally.
Scientists solved this problem by turning to the shark's eyes. The core of the ocular lens contains metabolically inert structural proteins known as crystallins, which are synthesized before birth during embryonic development. Because these central proteins do not turn over or regenerate throughout the shark's life, they preserve a chemical snapshot of the carbon isotopes present when the animal was formed. By isolating the innermost nucleus of the lens and using radiocarbon dating, researchers established an isotopic timeline for individual specimens.