Greenland shark

Lore & Background

The Greenland shark is a thickset species with a short, rounded snout, small eyes, and small dorsal and pectoral fins. Females are typically larger than males. Coloration ranges from pale creamy-gray to blackish-brown, with occasional whitish spots or faint dark streaks. The shark is often infested by the copepod Ommatokoita elongata, which attaches to the eyes and can cause near-blindness, but this does not seem to reduce life expectancy or predatory ability due to reliance on smell and hearing. As a generalist feeder, it consumes a variety of available foods, including carrion, fish (herring, salmon, cod, halibut, and others), seals, and even minke whale. When feeding on large carcasses, it employs a rolling motion of its jaw, using thin upper teeth as anchors while broad lower teeth cut chunks. The shark is sluggish and slow-moving, with an average swim speed of 0.34 m per second, and is thought to ambush sleeping seals. It contains many transposable elements, but also unique DNA repair genes that may mitigate damage. Its blood has three major types of hemoglobin adapted to deep-water pressure, and its vision relies on rod-dominated retinas and a tapetum lucidum for low-light conditions.

Reader's Guide

Its habitat in deep, cold waters of the North Atlantic and Arctic Oceans has made it poorly studied, but recent genomic research provides clues to its DNA repair mechanisms and low-oxygen adaptations. The shark's role as an apex predator and scavenger in Arctic ecosystems, along with its unusual parasitic relationship with the copepod Ommatokoita elongata, highlights the complexity of deep-sea food webs. Culturally, its toxic meat, treated to produce the Icelandic delicacy kæstur hákarl, underscores human adaptation to extreme environments. The Greenland shark's legacy lies in challenging assumptions about vertebrate aging, metabolism, and sensory biology, while remaining a symbol of the mysterious deep northern oceans.

Did You Know?

• The copepod Ommatokoita elongata attaches to the shark's eyes, often causing near-blindness, but the shark relies on smell and hearing.
• Greenland shark meat is toxic to mammals due to high levels of trimethylamine N-oxide, but is eaten in Iceland as kæstur hákarl after treatment.

Common Misconceptions (Editorial)

Some people assume the Greenland shark’s near-blindness from eye copepods shortens its lifespan or cripples its hunting ability, but the facts show the shark relies on smell and hearing and that the condition does not reduce life expectancy or predatory ability. Others may think it is a fast, agile predator, but the record notes it is sluggish and slow-moving, averaging just 0.34 m per second, and likely ambushes sleeping seals.

Why It Matters (Editorial)

The Greenland shark endures as a symbol of biological resilience, surviving in extreme cold and darkness while outliving every other vertebrate on the planet. Its unique adaptations—from DNA repair genes to hemoglobin suited for crushing depth pressures—remind us how much we still have to learn from species hidden in the ocean’s most remote corners.