Buzz
Not all creatures thrive in cold climates. Humans, for instance, are best suited to temperate zones and rely on clothing for warmth.
Certain species, however, excel in icy conditions, with adaptations so extreme that removing them from their freezing habitats would be cruel. Some are so uniquely suited to the coldest, high-pressure regions of the planet that they seem almost extraterrestrial.
1. Antarctic krill
Wikimedia Commons
These small crustaceans, essential to the diets of numerous larger Antarctic species, might seem similar to krill found elsewhere. However, weighing less than two grams each—equivalent to about 10 grains of rice—they gather in colossal swarms exceeding 500 million tonnes, more than double the weight of the global human population. Their daily vertical migrations influence ocean currents, help sequester atmospheric carbon into the deep sea, and supply nutrients to nearly every marine organism in the Antarctic ecosystem.
2. Antarctic Salps
Larry Madin/Woods Hole Oceanographic Institution
Salps, the unsuspected rivals of Antarctic krill, are colonial tunicates resembling jellyfish but genetically closer to vertebrates. Unlike krill, which depend on phytoplankton blooms, salps reproduce rapidly, outpacing krill in population growth. These barrel-shaped creatures conserve energy by drifting, allowing them to focus on reproduction. They can deplete phytoplankton before krill can fully utilize it, and their gelatinous bodies disrupt zooplankton communities. While krill are nutrient-rich, salps are mostly water, offering little nutritional value. Their increasing presence in the Southern Ocean, once rare, now endangers krill-dependent species, forcing them to migrate or face extinction.
3. Bowhead Whale
In the Arctic, the colossal bowhead whales glide through icy waters, feeding on minuscule copepods. Unlike their rorqual relatives, such as blue and fin whales, which gulp and filter water to trap prey, bowheads swim steadily with their mouths open, continuously sieving zooplankton. This feeding method resembles that of basking sharks more than other baleen whales. With blubber up to 20 inches thick, bowheads are well-insulated against the Arctic chill. The cold environment may also contribute to their remarkably long lifespans, potentially reaching 250 years, though historical whaling has made it challenging to confirm this.
4. Narwhal
The narwhal, a distinctive Arctic dweller, belongs to the toothed whale family yet possesses almost no teeth. Its iconic “horn” is actually an elongated left canine tooth, found exclusively in males. Historically mistaken for unicorn horns, these tusks were highly prized and traded for fortunes. Modern research reveals the tusk is highly sensitive and likely serves dual purposes: as a secondary sexual trait for courtship and as a tool to disturb seafloor sediment, uncovering flatfish prey. Toothless narwhals rely on suction to consume their bottom-dwelling meals.
5. Greenland Shark
A deep-sea neighbor of the narwhal, Greenland sharks are a member of the “sleeper shark” family—and the family name fits them well. Slow moving, slow living, and slow breathing, these sharks can still, slowly, end up reaching the size of a great white (21 feet long, and weighing over a ton).
Due to their extreme habitat depths (up to 7200 feet) and icy surroundings, studying live Greenland sharks is challenging. Known as apex predators, they also scavenge, with stomach contents revealing horses, polar bears, and reindeer. Given their sluggish speed of 1.6 mph and the improbability of these animals swimming in Arctic waters, it’s clear the sharks didn’t hunt them.
Greenland sharks are remarkable survivors, with lifespans potentially exceeding 200 years. Their flesh contains toxins adapted to deep-sea pressures, yet it’s consumed as a delicacy in Iceland. After months of aging to neutralize neurotoxins (though not ammonia), the dish hákarl remains a traditional treat, though younger generations increasingly avoid it.
6. Giant Scale Worms
Smithsonian Institution
One species of giant Antarctic scale worm (Eulagisca gigantea, above) gained internet notoriety last year, often mistakenly labeled as a new discovery despite being known since the 1920s. Its fearsome reputation stems from its ability to evert its pharynx, revealing a set of intimidating jaws.
Despite their online infamy, Antarctic scale worms are resilient scavengers, consuming everything from detritus and carrion to other invertebrates and small fish. While scale worms exist globally, only the Antarctic varieties grow to such enormous sizes. Their bristles, much like the “fur” of caterpillars, are highly irritating to human skin, making them best avoided.
7. Antarctic toothfish
Wikimedia Commons
The Antarctic toothfish, a relative of the Patagonian toothfish (marketed as “Chilean sea bass”), inhabits deeper, colder waters. Growing over six feet long and weighing up to 250 lbs, it dwarfs other fish in the Southern Ocean. This apex predator feeds on smaller fish, including its own young, and possesses antifreeze glycoproteins in its blood, enabling survival in the planet’s coldest waters. It serves as a crucial food source for Antarctic giants like colossal squid and sperm whales.
8. Antarctic proboscis worm
Wikimedia Commons
At first glance, the Antarctic proboscis worm might resemble misplaced intestines, but this bizarre creature is a marvel of adaptation. Unlike most ribbon worms, which are under 8 inches long, the Antarctic variety can stretch up to 7 feet, yet weighs no more than 5 ounces—lighter than many smartphones. Equipped with a barbed, sticky proboscis, it hunts prey and scavenges carrion. Its highly acidic body (pH , akin to lemonade) and gelatinous composition make it unappealing to most predators.
9. Crocodile Icefish
Wikimedia Commons
While some fish develop antifreeze proteins to endure Antarctic waters, crocodile icefish take a more radical approach: they lack hemoglobin entirely. This unique family of 16 species is the only known vertebrate group to evolve a circulatory system without red blood cells. Although their genome retains traces of hemoglobin-coding genes, their ancestors lost the ability to produce red blood cells, leaving them with a highly unconventional oxygen transport system.
Surprisingly, this adaptation offers no evolutionary advantage. During the Tertiary period, a predator shortage and oxygen-rich Antarctic waters allowed hemoglobin-free fish to survive through inefficient direct oxygenation. Today, crocodile icefish thrive despite their inefficiency, compensating with enlarged blood vessels, double the blood volume, and a heart output five times greater than similarly sized fish. Yet, their lack of hemoglobin remains a biological oddity rather than a benefit.
10. Antarctic Sea Spiders
Keith Martin-Smith/Antarctica.gov.au
Sea spiders, unrelated to true spiders, are typically tiny globally, with muscles often just one cell long. In Antarctica, however, they exhibit gigantism, growing up to 10 cm long with leg spans of 40 cm. Despite their size, they lack a respiratory system, relying on diffusion for oxygen. They feed on soft-bodied invertebrates like sea anemones, using a proboscis to extract nutrients. Uniquely, male sea spiders care for the eggs, carrying them until they hatch after the female deposits them.
11. Colossal Squid
The Southern Ocean wouldn’t be the same without the colossal squid, though its presence adds an element of terror. These deep-sea dwellers thrive under immense pressure, rarely venturing near the surface. Found as far north as Patagonia and New Zealand, they predominantly inhabit the Antarctic depths. While their tentacles are shorter than those of giant squid, their bodies are over twice as long and three times heavier. With eyes nearly a foot wide—the largest of any animal—they are ambush predators, feeding mainly on toothfish and serving as a key food source for sperm whales, accounting for 75% of their biomass intake. The rotating hooks on their tentacles leave deep scars on the whales that hunt them.
