Greenland sharks are a top predator for predatory fish. However, hunting has never been observed. Clearing reports is common. Sharks replenish their diet with reindeer, moose, horses, polar bears and seals. Although sharks feed on seals, researchers are still unclear how it kills them. Because it lives in cold water, the metabolic rate of Greenland sharks is extremely low. In fact, its metabolic rate is so low that the swimming speed of the species is the lowest compared to the swimming speed of any fish, so it cannot swim fast enough to capture seals. Scientists assume that sharks may catch seals while they sleep. Low metabolic rates also cause slow and longevity in animals. Because sharks have cartilage defects rather than bones, dating their age requires a special technique. In a 2016 study, scientists performed radiocarbon dating on crystals in the crystals of captured shark eyes. The oldest animal in the study is estimated to be 392 years old, plus or minus 120 years. From these data, Greenland sharks have a life span of at least 300 to 500 years, making them the longest-lived vertebrates in the world. The biochemistry of Greenland sharks adapts to the survival of fish at extremely cold temperatures and high pressures. The shark’s blood contains three types of hemoglobin that allow the fish to obtain oxygen within a certain pressure range. Sharks are said to smell like urine because their tissues contain large amounts of urea and trimethylamine N-oxide (TMAO). These nitrogenous compounds are wastes, but sharks use them to increase buoyancy and maintain homeostasis. Most Greenland sharks are blind, but not because their eyes are small. Instead, the eyes are colonized by copepods, obscuring the fish’s field of vision. Sharks and copepods may have a symbiotic relationship, and crustaceans show bioluminescence, attracting prey to eat sharks. Little is known about the breeding of sharks in Greenland. Females are born of ovum, and about 10 pups are laid in each litter. Newborn pups are 38 to 42 cm (15 to 17 inches) long. Based on the slow growth rate of animals, scientists estimate that it takes about 150 years for sharks to reach sexual maturity. The high concentration of TMAO in Greenland shark meat makes it toxic. TMAO is metabolized to trimethylamine, causing potentially dangerous poisoning. However, shark meat is considered a delicious dish of Iceland. The meat is detoxified by drying, repeated boiling or fermentation.