Deep-Sea & Ocean Animals

The Anglerfish fishes with a glowing lure that grows right out of its own forehead.

Why it works: The glowing "fishing rod" on the anglerfish's head is really a stretched-out fin spine, and the bright bulb on its tip is packed with billions of tiny living bacteria. The fish can't make light on its own, so it grows these bacteria inside the bulb and feeds them; in return, a chemical reaction inside the bacteria combines with oxygen to give off a blue-green glow. A young anglerfish actually takes the bacteria in from the seawater around it. Its very stretchy stomach and loose jaw let it swallow prey bigger than itself, and the strange mate-fusing trick works because anglerfish lost part of the immune defense that would normally reject another fish's body.

The Cone Snail fires a hollow harpoon-shaped tooth loaded with paralyzing venom to spear passing fish.

Why it works: A cone snail turns one of its own teeth into a tiny hollow harpoon, like a dart with a barb on the end. Muscles squeeze a venom gland to pump venom down through the hollow tooth and inject it into a fish, the same way a needle injects. The venom is a mix of chemicals called conotoxins that jam the fish's nerve "switches" (the ion channels that let sodium, potassium, and calcium flow in and out of nerve cells), so the nerves can't send messages and the fish can't move. One of these conotoxins blocks calcium channels that carry pain signals, which is why a copy of it became a painkiller (ziconotide/Prialt) stronger than morphine.

The Cuttlefish hypnotizes its prey by pulsing moving bands of color across its skin, freezing the target in place.

Why it works: The cuttlefish's skin is packed with tiny color sacs called chromatophores, and each one is ringed by little muscles its nerves can yank open or snap shut. Because muscles and nerves do the work (not slow chemicals), the color flips almost instantly, and mirror-like cells underneath bounce light to add blues, greens, and silver. When it hunts, it rolls dark stripes across its body; scientists think this swirling motion overloads the prey's eyes so the crab or fish can't tell the cuttlefish is creeping closer. And even though it is colorblind, it seems to match its background by reading how light or dark each spot is rather than the actual color.

The Flamingo turns its own color pink by eating it, since it hatches a dull grey.

Why it works: A flamingo's food (algae and brine shrimp) is packed with natural orange-red coloring chemicals called carotenoids. When the flamingo digests its meal, its body breaks these chemicals down and carries the pink color into its growing feathers, legs, and bill, so the bird literally builds its color out of what it eats. A chick hatches grey because it hasn't eaten enough yet; if any flamingo eats a poor, carotenoid-low diet, no new pink gets stored and it fades toward white. Parents make red 'crop milk' in their throat that is loaded with these same pigments, so giving it away drains their own color and turns them temporarily pale.

The Giant Squid has the largest eyes of any animal alive, roughly the size of a human head.

Why it works: In the deep sea it is almost pitch black, so bigger eyes help by catching more of the tiny bit of light that's there — just like a wider bucket catches more rain. The giant squid's dinner-plate eyes gather so much light that they can spot a very faint glow: when a hungry sperm whale swims by, it bumps tiny ocean creatures that flash with light (this living glow is called bioluminescence), making a glowing trail. Scientists think eyes this huge let the squid see that trail far away and flee. Some scientists do debate it, though — the giant eyes may partly just come from having a giant body.

The Hagfish turns the water around it into liters of choking slime in under a second.

Why it works: Each slime gland is packed with two tiny ingredients: little coiled bundles of protein thread (each wound up like a ball of wool) and small packets of mucus. When the hagfish shoots them into seawater, the mucus packets soak up a huge amount of water and swell into a fine gel, while the threads unravel and tangle through it. The mucus is the part that actually clogs: it spreads into spaces so small that water can barely flow through, so it jams a predator's gills and makes breathing very hard. The threads work like a net that holds the gooey gel together and keeps it stuck to the gills, so it doesn't just wash away. Together they turn a teaspoon of goo into liters of stretchy, watery slime in under a second.

The Immortal Jellyfish can avoid dying of old age by folding back into a baby and growing up again.

Why it works: When this jellyfish is hurt, starving, or just getting old, its grown-up body cells don't keep dying. Instead they actually change into different kinds of cells, a switch scientists call transdifferentiation. Using that trick, the whole jellyfish collapses into a little blob and rebuilds itself as a polyp, the baby stage stuck to the seafloor, which then grows brand-new jellyfish. Because its cells can keep re-switching, there's no known limit to how many times it can restart, though it can still be eaten or get sick and die.

The Leaf Sheep runs on sunlight like a living solar panel.

Why it works: A chloroplast is a tiny green machine inside plant and algae cells that uses sunlight to make sugar. The leaf sheep eats green algae but does not destroy these machines. Instead it stores the still-working chloroplasts in the leafy parts on its back, where they keep catching sunlight and making food the slug can use. Scientists are still puzzling out exactly how the slug keeps these stolen machines alive for so long, since it does not carry the algae's repair instructions.

The Leafy Sea Dragon grows leaf-shaped flaps of skin that mimic floating seaweed so perfectly it becomes almost invisible.

Why it works: The leafy flaps aren't real leaves; they are thin lobes of skin (called dermal appendages) that grow out from the dragon's body in shapes that match floating, broken-up seaweed. Because they look and drift like the kelp and weed all around it, predators and prey can't pick out the dragon's outline, so it seems to vanish. The flaps do no swimming at all. Instead, the dragon glides by rippling two tiny see-through fins, one on its back and one near its head, fast enough that the moving fins are very hard to see, which keeps the seaweed disguise unbroken.

The Mantis Shrimp throws the fastest punch on Earth, at the speed of a bullet.

Why it works: The shrimp's club isn't powered by muscle alone. Muscles slowly bend a tiny springy, saddle-shaped piece of its shell, storing energy like a loaded bow, while a little latch holds it in place. When the latch lets go, all that energy releases at once, so the club shoots out at the speed of a bullet. It moves so fast the water behind it can't keep up and briefly turns to vapor, making bubbles that collapse with a flash of light and a burst of heat, adding a second hit. (Its eyes really do have up to 16 color receptors, but scientists found it doesn't see colors more finely than we do; it uses the extra receptors to recognize colors super-fast instead.)

The Mudskipper spends most of its life out of the water, walking and climbing on dry land.

Why it works: On land, a mudskipper still needs oxygen but can't pump water over its gills, so it uses three tricks at once. It carries a mouthful of water trapped in sealed-shut gill chambers so the gills stay wet and keep working, and it also soaks up oxygen straight from the air through its thin, wet, blood-rich skin and the lining of its mouth, the way a frog does. This only works while the skin stays damp, which is why a mudskipper keeps rolling in wet mud. To 'walk,' it swings both strong front (pectoral) fins forward at the same time, like a person on crutches, because those fins have extra-big muscles and a beefed-up shoulder to push its body along.

The Octopus has three hearts and nine brains.

Why it works: An octopus has two small "gill hearts" that push blood through its gills to load it with oxygen, plus one big "body heart" that pumps that fresh blood to the rest of its body. When it swims by squeezing water out like a jet, that squeezing also presses on the blood vessels feeding the body heart, so the heart can't beat well and the octopus gets tired fast. Crawling doesn't squeeze those vessels, so its body heart keeps beating happily, which is why crawling is the octopus's favorite way to get around.

The Pistol Shrimp snaps its claw fast enough to create a bubble nearly as hot as the surface of the sun.

Why it works: Here's the surprise: it's not the claw smacking shut that makes the bang. When the claw snaps closed, it squirts out a jet of water so fast that the water pressure inside the jet drops, and the water boils into a tiny vapor 'bubble' even though it's cold. A heartbeat later that bubble collapses and crushes the vapor inside so hard and so fast that it briefly heats to almost 5,000 degrees, flashes a speck of light, and bangs out a shockwave. So the heat, light, and loud crack all come from the bubble popping, not from the claw itself.

The Sea Cucumber shoots its own sticky internal organs out of its rear at attackers.

Why it works: The sea cucumber doesn't really fire its guts on purpose like a cannon — it uses water pressure. Many sea cucumbers store sticky threads called Cuvierian tubules inside their body, attached near their breathing parts. When a predator attacks, the animal squeezes its muscles hard, water rushes into the threads, and they shoot out the rear and stretch up to 20 times longer, getting sticky in seconds. The threads also hold a natural poison (a chemical called holothurin), so a tangled-up crab or fish gets a nasty, gluey surprise while the sea cucumber escapes and slowly regrows the parts it lost.

The Sea Otter holds hands while sleeping so it doesn't drift apart in the night.

Why it works: Sea otters have no blubber, so instead they trap a layer of warm air right against their skin. Their fur is so dense, up to about a million hairs in one square inch, that water cannot push through to reach the skin, and the trapped air acts like an invisible wetsuit. That is why otters groom for hours a day: combing in air bubbles and natural skin oils keeps the coat fluffy and waterproof. They also nap in groups called rafts, holding paws or wrapping in kelp so the current does not carry them apart while they sleep.

The Tardigrade survived the raw vacuum of space, completely unprotected.

Why it works: The tardigrade's secret is drying out on purpose. When its water disappears, it pulls in its head and legs and curls into a ball called a "tun," pushing out almost all of its water so its body chemistry nearly stops. To keep its squished cells and DNA from breaking while dry, it makes special protective molecules (including proteins scientists call CAHS, which turn the inside of the cell into a glass-like solid, and one nicknamed Dsup that shields its DNA). With its body switched off and protected this way, there is almost nothing left for cold, heat, radiation, or empty space to damage until water returns and wakes it up. Scientists are still working out exactly how all these tricks work together.