01. Most explosive defense
Name: bombardier beetles, Carabidae family.
Ability: mixing chemicals to create an explosion.
In the world of insects, ants can overcome almost anything. But these cool animals don’t always have it their own way. Bombardier beetles deliver an anti-ant surprise that is positively explosive. An ant, a spider or any other predator that, say, clamps on to a beetle’s leg with hostile intent instantly finds itself blasted with a chemical spray that’s as hot as boiling water.
So how does a small, cold-blooded creature manage to do this? Pure chemistry: in the rear of its abdomen are two identical glands lying side by side and opening at the abdominal tip. Each has an inner chamber containing hydrogen peroxide and hydroquinones and an outer one with catalase and peroxidase. When chemicals in the inner chamber are forced through the outer one, the chemicals react together, and the beetle has effectively created a bomb.
The resulting vapor, now containing the irritants known as p-benzoquinones, explodes from the end of the abdomen with a bang that’s audible to a human and a temperature that’s scalding to the would-be predator. What’s more, the beetle can rotate its abdomen through 270 degrees in any direction, so that it can aim with absolute precision, and if 270 degrees isn’t enough, it can shoot over its back, hitting a pair of reflectors that will ricochet the spray at the extra angle needed. Scientists find bombardiers fascinating because they’re the only animals known to mix chemicals to create an explosion.
02. Stickiest skin
Name: holy-cross, crucifix or Catholic toad, Notaden bennetti.
Ability: producing a super “superglue“.
Some of the world’s strangest creatures are found in Australia – a continent of extremes giving rise to extreme adaptations. The holy-cross toad lives where many other amphibians can’t: in hot, harsh areas inland, where droughts may last for several years. It uses its strong back legs to burrow down in the soil, where it sits out the heat of the day, and when drought sets in, it survives by digging a chamber a meter or so underground in which it aestivates (becomes dormant), emerging only when the rains return.
Like its close toad relatives, the holy-cross also has unique glands in its skin. If it is disturbed or distressed, these release a special secretion that turns into glue. The glue hardens in seconds and has a tensile strength five times that of other natural glues. This is particularly useful should ants attack, as even the biggest immediately get stuck to the toad’s skin. And since, like all frogs and toads, it sheds its skin and eats it about once a week, the holy-cross toad has the pleasure of swallowing the ants that attack it.
Scientists in Australia are now trying to produce an artificial glue as good as the toad’s. Holy-cross toad glue will stick plastic, glass, cardboard and even metal together. More importantly, it can repair splits in cartilage and other body tissues and therefore might prove to be a miracle adhesive that will help surgeons repair the most difficult of injuries.
03. Heaviest drinker
Name: broad-tailed hummingbird, Selasphorus platycercus.
Ability: can drink up to five times its body weight in a day.
To say this or any other hummingbird drinks like a fish is to understate how much it drinks. In proportion to its body weight, it drinks a lot more than a fish. (Just to get that cliché straight: freshwater fish don’t drink – they absorb water through their skin. Saltwater fish that drink don’t do so to excess.) In the case of the hummingbird, it’s the fault of the flowers. Hummingbirds have evolved to drink nectar. The flowers they visit have evolved to provide that nectar, and the nectar they provide is typically about 30 per cent sugar and the rest water. To keep their wings going at a rate quicker than the human eye can see – to hover – hummingbirds need a huge amount of sugar, which means that by drinking nectar these cool animals take in up to five times their body weight in water every day.
If any other animal, including a human, tried to drink even one times its body weight, it would be dead long before it could do it. So while hummingbirds were evolving beaks to fit into the flowers with their watered-down nectar, they were also having to evolve nature’s heaviest-duty kidneys. Some water just passes through the bird unprocessed, but 80 per cent goes to the kidneys to be expelled as very dilute urine. And why the broad-tailed in particular? It’s simply the most energetic hummingbird, and thus the most supersaturated.
04. Best mimic
Name: Indo-Malayan mimic octopus.
Ability: pretending to be anything but an octopus.
If you are a medium-sized predator, the average octopus is one of the most edible animals in the sea. It’s substantial and meaty, and without a shell, bones, spines, poisons or any other unpleasant defense mechanisms. In fact, the best defense most species of octopus have is to stay hidden as much as possible and do their own hunting at night.
So to find one in full view in the shallows in daylight was a surprise for two Australian underwater photographers, swimming off the Indonesian island of Flores in the early 1990s. Actually, what they saw at first was a flounder. It was only when they looked again that they saw a medium-sized octopus, with all eight of its arms folded and its two eyes staring upwards to create the illusion of a fishy body. An octopus has a big brain, excellent eyesight and the ability to change color and pattern, and this one was using these assets to turn itself into a completely different creature.
Many more of this species have been found since then, and there are now photographs of octopuses that could be said to be morphing into sea snakes (six arms down a hole, and two undulating menacingly), hermit crabs, stingrays, crinoids, holothurians, snake eels, brittle stars, ghost crabs, mantis shrimp, blennies, jawfish, jellyfish, lionfish and sand anemones. And while they mimic, these cool animals hunt – producing the spectacle of, say, a flounder suddenly developing an octopodian arm, sticking it down a hole and grabbing whatever’s hiding there.
05. Hottest animal
Name: Pompeii worm, Alvinella pompejana.
Ability: withstanding scalding water.
The Pompeii worm thrives in large colonies in one of the darkest, deepest, most hellish places on Earth – close to a geyser of water so hot it could melt the worm in a second. It is also subject to a pressure great enough to crush a person and doused in a soup of toxic sulphur and heavy metals. Communities of Pompeii worms cling to the sides of ‘smokers’ 2–3 km (1.2–1.9 miles) under the sea. These belching chimneys grow over hydrothermal vents on volcanic mountain ranges, created from the chemicals that precipitate out as 300 °C (572 °F) vent water meets cold seawater.
To survive on a smoker requires super-worm strategies. For its home, the worm makes a paper-like hemical-and-heat-resistant tube. For a thermal blanket, it ‘grows’ a fleece of filamentous bacteria, feeding it with sugar-rich mucus secreted from its back. This blanket may also detoxify the vent fluid in its tube.
Unlike the vent tubeworm Riftia pachyptila, the Pompeii worm has a gut and ‘lips’ which it extends to ‘graze’ on bacteria that grow on the surface of the colony. But no one knows quite how it copes with what are the highest temperatures and temperature gradients experienced by any organism apart from bacteria, for though it angles its head (gills, mainly) away from the hottest water, its tail experiences flushes hotter than 80 °C (176 °F). Keen to make use of the Pompeii worm’s technology for human endeavors, scientists are now racing against each other to unravel its survival secrets.
06. Most shocking animal
Name: electric eel, Electrophorus electricus.
Ability: stunning prey with electrical discharges.
Think of it as a living battery. The electric eel can grow to be more than 2 m (6 ft 5 in) long, but its organs are packed just behind its head, leaving 80 per cent of its body to electricity generation. It’s stacked with up to 6,000 specially adapted muscle cells, or electrocytes, aligned like cells in a battery. Each electrocyte emits low-voltage impulses that together can add up to 600 volts – enough to render a human unconscious. The positive pole is behind the eel’s head, and the negative pole is at the tip of its tail. It tends to remain straight when swimming, using its long ventral fin for propulsion, and so keeps a uniform electric field around itself.
Electricity affects almost every bit of the eel’s behavior. As well as stunning or killing with high-voltage pulses, it communicates with other eels electrically and uses electrolocation (a sort of electrical bounce-back system) to detect objects and other creatures in the water. Fish and frogs are its staple prey, and it can detect the minute electric currents these and other living things produce. The eel can’t see well, but this doesn’t matter much, since it is mainly nocturnal and tends to live in murky water.
There are other electrified fish, including the related knifefishes, which generate a weak electric field around themselves that they use to sense objects and fish prey and to communicate. The only other shockers are the torpedo ray and the electric catfish, but neither is as shocking as the electric eel.
07. Coldest animal
Name: wood frog, Rana sylvatica.
Ability: withstanding being frozen for week.
There’s an African midge so well adapted to drought conditions that, as a sideline, it can withstand being artificially frozen to –270 °C (–454 °F). Lots of other insects can survive freezing, too, but the creatures that can withstand cold for the longest period are probably bacteria in Antarctica.
The most freeze-tolerant higher animal is the wood frog, which can literally become a “frog-sicle”, enabling it to live further north than any other amphibian and to hibernate close to snowmelt ponds, presumably to give it a head start and enable it to reproduce quickly before the ponds dry.
When the temperature drops below freezing, the frog’s liver starts converting glycogen to glucose, which acts as an antifreeze. The blood passes the glucose to the vital cells, which are then protected from freezing on the inside, all the way down to –8 °C (18 °F). But the rest of the frog’s body fluids, up to 65 per cent of them, turn to ice and the organs, deprived of blood, actually stop working. Even the eyeballs and the brain freeze. It is effectively the living dead. (The painted turtle Chrysemys picta can do this, too, but only briefly.) When a thaw comes, the frog’s heart starts beating and pumps blood containing clotting proteins around the body, which stops bleeding from wounds caused by the jagged ice crystals. The frogsicle quickly comes back to life and, just as miraculously, so do the frozen parasitic worms in its body.
08. Most bizarre defense
Name: Texas horned lizard, Phrynosoma cornutum.
Ability: blood squirting.
Revered by native peoples for thousands of years, the Texas horned lizard has an array of abilities. It eats mainly ants – and lots of them, since much of an ant is indigestible. This necessitates a huge stomach. Eating more than 200 ants a day means exposure in the open for long periods, and being stomach-heavy means a horned lizard finds it difficult to scamper away from predators. Instead, it relies on an armory of defenses. It has camouflage coloring, with an outline broken by spines and outgrowths, and it will freeze if a predator approaches. Its horns and spines can pierce the throat of a snake or bird, and it can hiss and blow itself up to look even more fearsome. When it comes to coyotes, foxes and dogs, a horned lizard’s most spectacular defense is to squirt foul-tasting blood from sinuses behind its eyes. That usually has the desired effect. But it squirts only when it’s provoked, since it risks losing up to a quarter of its blood.
Such abilities are, however, no defense against human invasion of its land. Its strange shape and coloring has made it attractive to reptile collectors, and its habit of freezing means it is prone to being run over. And with humans have come exotic fire ants, which it can’t eat and which are replacing the native ants on which the lizard depends – a sorry way for such a determined survivor to go.
09. Stickiest spitter
Name: spitting spider, Scytodes species.
Ability: snaring and immobilizing prey with sticky spit.
The spitting spiders are most closely related to the venomous brown recluse spiders. Like the brown recluses, they have only six eyes (as opposed to eight) and relatively poor vision. But they make up for it with their snaring skills. Their main sense is touch and, as the spiders walk, their two front legs, which are longer than the other six, tap the ground ahead, feeling for something edible.
Like all spiders, these cool animals lay land lines that they periodically tack down with fast-drying silk, which keep them from falling – just like the ropes of a mountain climber. Many spiders can tell if an insect or another spider crosses these lines, and some spiders are thought to use sensitive hairs on their forelegs to detect something without actually touching it – a form of hearing – while others just feel around. But what all spitting spiders do, once their prey is located, is rear back and spit at it.
With unerring accuracy over a distance that can be more than five times its body length, a spider ejects a gooey mixture of silk and venom. This stuns and immobilizes the prey so that the spider can scurry over, bite it to inject more venom and eat it. One probable reason for killing at a distance is that spitting spiders are comparatively small and their jaws don’t open wide enough to do more than bite a leg or antenna. The net-like sticky spit also enables them to snare prey that moves faster than they do.
10. Most inflatable animal
Name: pufferfish, Diodon holocanthus.
Ability: transforming itself into a spine-covered “balloon”.
This could also be the creature with the greatest number of common names. In English alone, these include spiny puffer, porcupinefish, balloon porcupinefish, brown porcupinefish, blotched porcupinefish, freckled porcupinefish, longspring porcupinefish, hedgehogfish and balloonfish – all of which refer to its defensive quills, its ability to expand, or both. When relaxed, the pufferfish looks pretty ordinary. But if it’s attacked, it can suddenly blow itself up to become a spine-covered sphere three times its original size, like a basketball with hundreds of long, thin nails sticking out of it. It does this by taking many rapid gulps of water.
Its stomach, which in the course of evolution has come to be used for nothing else (food is not digested there but passed straight to the intestine), is folded in pleats when the fish isn’t puffed up. In fact, there are pleats within pleats within pleats – right down to pleats that can only be seen with a microscope.
When the fish perceives danger, it pumps in water, the stomach unfolds, the skin expands, and the scales – which ordinarily lie backwards against the skin – spring up as spines. As well as dispensing with the normal function of its stomach, the pufferfish has lost most of its skeleton except its backbone (ribs, in particular, would obviously interfere with expansion). A similar sort of oral pumping can also be used offensively: the pufferfish’s close relative, the triggerfish, sucks in water and then shoots it out again at sea urchins, flipping them over to reveal their soft undersides.
11. Fastest flying animal
Name: peregrine falcon, Falco peregrinus.
Speed: can be more than 300 kph (186 mph) when plunge-diving.
The fastest bird (and, indeed, the fastest-moving wild animal of any kind) is certainly a bird of prey and very probably the peregrine falcon. When “stooping”, or plunge-diving, to catch a bird in midair, a peregrine weighing just over 1 kg (2.2 lb) could, theoretically, reach a maximum velocity of 385 kph (239 mph) in a 1,254 m (4,113 ft) free-fall. Though there is a difference between how fast it could fly and how fast it actually does fly, a peregrine diving with a skydiver has been filmed at stooping speeds exceeding 322 kph (200 mph), which is exceedingly close to the theoretical maximum.
What’s strange about a peregrine’s plunge-dive, though, is that, when the bird is within 1.8 km (1.1 miles) of prey, it will fly in a curved path. Biologists now think they know why.
A peregrine’s vision is such that it sees best when its head is 40 degrees to one side, but to angle its head like this at high speed would cause drag. It is therefore faster for a peregrine to dive on a curve because it can hold its head straight while still keeping its prey in view.
But such flight is not conventional flapping flight. The wandering albatross currently holds the record for the fastest sustained flight, with one individual achieving 56 kph (35 mph) sustained over more than 800 km (497 miles). Albatrosses, though, use “dynamic soaring”, harnessing the power of the wind to glide rather than flapping continuously.
12. Greatest sticking power
Name: geckos, Gekkonidae family.
Ability: clinging on to any surface.
Most people would think that geckos hang from the ceiling, or any other surface, by suction or perhaps with the help of claws and adhesive. But their sticking power is far more remarkable.
Each foot is covered with half a million microscopic little filaments, called setae, from each of which sprout more than a thousand cauliflower-like fibres, known as spatulae. When these spatulae splay, these interesting animals are so close to the surface that a tiny charge is generated between their molecules and those of the surface, which draws them to each other, the positive pole of one attracting the negative pole of the other. This is enhanced by the geckos’ mechanism of toe uncurling, which enables them to attach and peel off their feet 15 times a second while running. The molecular force is so strong that a foot on glass, with its millions of spatulae all generating molecular force, could support 40 kg (88 lb).
This mechanism also includes a self-cleaning component: any dirt attached to the setae falls off after just a few steps, the attractive forces between the dirt and the setae being less than those between the surface and the dirt. The geckos’ cling-on capacity is inspiring technologists to develop everything from a self-cleaning, easily detachable adhesive tape to sure-footed micro-robots for use in space. Jumping spiders, though, almost certainly got there first, being able to support up to 170 times their own weight using the same molecular mechanism.
13. Strongest animal
Name: rhinoceros beetle, Xylotrupes gideon.
Ability: lifting possibly up to 850 times its own weight.
Rhinoceros beetles belong to the scarab family, many of which are so incredibly strong that these cool animals can do things like roll huge dung balls or bury other animals. But the rhinoceros beetle is supposedly the strongest: one laboratory animal reputedly lifted a weight on its back 850 times its own weight, far exceeding the relative strength of an elephant.
Even if the record is exaggerated, there is no doubt about the beetle’s strength. Males are famous for their forked ‘horns’: an enormous one arching over the head and a smaller one arching up to meet it. When females are ready to mate (they spend most of the time below ground, feeding on plant material and possibly keeping out of the way of males), they waft out an attractive pheromone scent that brings males flying in. This is when the horns clash. The biggest beetles – heaviest and longest – are those that have fed on the best food and so, possibly, have the best potential to father offspring. But they must prove themselves to onlooking females. Duelling males first threaten each other with head bobbing. Then the head-butting, levering and tossing starts, the loser finally being prized off his perch. The bigger a male is, the bigger his horns, the stronger his muscles and gripping legs, and the more likely he is to win. But bigger isn’t always better. In the case of some horned scarab beetles, males that have invested in huge horns turn out to have small genitalia.
14. Fastest digger
Name: aardvark, Orycteropus afer.
Ability: digging for a living.
The aardvark is one of the world’s strangest mammals. It has no close relatives alive today, though distant ones include elephants, manatees and golden moles, and no animals behave quite like it. Aardvark is Dutch for ‘earth pig’ and, being plump and hairless, it makes a juicy meal. A nocturnal lifestyle, combined with a good sense of smell and radar-like ears, helps it to evade some predators. But its chief means of defense is burrowing. It has long, chisel-like claws at the end of enormously powerful, muscular legs, and these make it possibly the fastest-burrowing animal in the world.
Reputedly, it can dig a burrow in soft earth faster than two men with spades. The burrows it digs as daytime sleeping dens also act as bolt-holes and are long enough – often more than 10 m (33 ft) or so – to dissuade a predator such as a hyaena from trying to dig out the aardvark or its babies.
The claws are also designed for digging termites and ants out of hard-baked earth. In fact, the aardvark’s whole body is devised for anting. At night, it zig-zags across the savannah with its snout down, and as soon as it detects a termite nest, it starts digging. Nose hairs filter out dust, and its 45 cm (17 in) long, saliva-wet tongue extracts termites and ants at speed. Its termite-grinding teeth grow continuously but lack roots or enamel. A life of digging and dirt seems to work, though, as aardvarks are found in most parts of Africa where ants and termites abound.
15. Best water-walker
Name: water skater, or water strider, Gerris species.
Ability: walking on water as if it were dry ground.
“Water skater” is a more appropriate name than “water strider” for this remarkable insect, as it uses the surface tension of still water, such as on ponds, almost as though it were a layer of thin ice. Surface tension is not something that big, heavy animals notice much, but what happens is this: below the surface, molecules of water are attracted towards other molecules of water in all directions – up, down and sideways. At the surface, though, the molecules cannot go further upwards, and so it’s all sideways and down. This creates what amounts to a physical film firm enough to support something very light.
The skater’s long legs also have microscopic hairs that trap air and make the legs more hydrophobic, or water-repellent, and the more hydrophobic something is, the heavier it can be and still be supported by the surface tension. The skater’s legs don’t get wet at all. As the insect moves across the water at speeds of up to 75 cm (30 in) a second, it makes little indentations, or dimples, in the surface tension and then uses the dimples as though they were the blades of oars – in fact, it rows across the water. And it only runs (or rows) on four of its six legs. The front two are very short and sensitive. They can tell when something breaks the surface, and if that something is small and keeps moving, the strider will dart over, grab it and eat it.
16. Most elastic tongue
Name: chameleons, Chamaeleonidae family.
Ability: capturing prey with a bowstring, suction-cup, accordion tongue.
At first analysis, a chameleon shouldn’t be able to do what it does. It’s spectacular enough that in just ten seconds the lizard can become an entirely different color, but the way it uses its tongue makes even that seem pedestrian.
X-ray film and high-speed video have revealed that a chameleon’s tongue on its way to an insect starts relatively slowly but then accelerates to 6 m (20 ft) a second in just 20 milliseconds. This is a faster acceleration than sheer muscular force could ever manage. Then when the tip of tongue reaches the target, which can be more than two of the chameleon’s body lengths away, it can attach to prey as heavy as 15 per cent of the chameleon’s own weight (large ones can grab birds or lizards) and, with nothing on the tongue stickier than viscous saliva, can haul the prey back quickly and easily.
How? First, the shot: it’s been discovered that between its tongue bone and tongue muscle a chameleon has some elastic collagen tissue that the muscle stretches before the tongue is released, the same way a bowstring is stretched to shoot an arrow. Second, the grab: there’s another muscle at the tip of the tongue that contracts in the instant before the prey is hit, converting the tip from convex to concave and making a powerful suction cup. Third, the retrieval: more tongue muscles and special filaments allow for “supercontraction”, like an accordion slammed shut. And it all happens in a little more than a second.
17. Best glider
Name: Japanese giant flying squirrel, Petaurista leucogenys.
Ability: flying – almost.
Flying squirrels don’t really fly. These cool animals don’t have wings that they flap to give themselves thrust. But they do glide. Along with five other classifications of mammal, and certain lizards and snakes, they glide between trees to save energy and to avoid the dangers implicit in scurrying along the ground.
The best of the gliding animals (aside from wind-surfing birds) would be the one whose glide is longest, most agile and comes closest to flight. A typical glider goes near enough in a straight line from the tree it was in to the tree it’s aiming for, floating on the out-spread membranes between its fore and hind legs. But the giant flying squirrel is more agile than that. By changing the position of its legs, it can alter its direction and perform impressive fast turns and banks. It can even ride the warm air currents rising from the valleys in its native mountain home, like a soaring bird.
Its close relative, the giant red flying squirrel, is also an outstanding glider and the two species can travel further than any other non-flying glider – more than 110 m (361 ft). To travel such long distances, and to get up speed, they simply hold their legs close to their bodies and fall. They hurtle towards the ground at a heart-stopping rate and then open their membranes – and glide.
18. Fastest sprinter
Name: cheetah, Acinonyx jubatus.
Speed: up to 103 kph (64 mph).
A cheetah actually spends most of its time resting from the heat, hiding from other big cats or sitting high up looking for prey. But the action, when it happens, is sudden. After stalking its prey as closely as possible, it sprints from almost a standing start. Film of one chase showed the cheetah reaching 80 kph (56 mph) in just three seconds. But the official record was set by a cheetah in Kenya that clocked an average 103 kph (64 mph) over 201 m (220 yds).
At top speed, a cheetah’s incredibly flexible spine gives it a stride length relatively twice that of a racehorse’s – so long that all four feet are off the ground for more than half the distance. Other design features include tough, gripping pads, non-retractable claws like running-shoe spikes, very long, thin, tendon-spring legs, a rotary gallop that allows it to make sudden changes in direction and a long tail to help balance those moves.
A cheetah doesn’t always run at top speed, however, and usually gives up after 60 seconds. The average chase is no further than 200–300 m (219–328 yds) and no more than 20 seconds, after which the animal, panting frantically, has to rest for at least 20 minutes to cool off and to let the build-up of lactic acid from its super-speed muscles dissipate. Not surprisingly, prey animals such as impalas and gazelles have evolved to run fast, too – a Thomson’s gazelle has been recorded at 94.2 kph (58.5 mph), fast enough to keep any cheetah on its toes.
19. Flattest animal
Name: leptocephalus, or glass eels, Anguilla species.
Size: elongate and leaf thin.
None of the flat, transparent animals in the oceans are quite as fascinating, or as long, as leptocephali. Eels as a group have one of the most eventful life cycles on the planet, and it all starts with a leptocephalus, ancient Greek for ‘slender head’. This refers to the head on the larva of the European eel Anguilla anguilla – the best studied of the eels and a source of fascination since Aristotle declared that eels came from earthworms. It wasn’t until 1893, though, that anyone made the connection between the European eel and what had been known as Leptocephalus brevirostris. And it’s no wonder. Who would have thought a 1–2 mm (0.04–0.08 in), transparently flat, slightly fish-shaped thing in the sea was the same animal as the familiar snaky inhabitant of European fresh water?
This is what biologists believe happens: at about 10–14 years of age, adult eels get the over-whelming urge to swim down river and across the Atlantic to the Sargasso Sea. How and why is a mystery. It’s believed that they spawn in the Sargasso (but no one has seen them doing it) and die. The eggs hatch into leptocephali, which drift in the Gulf Stream for three years, finally reaching Europe. Now 4.5 cm (1.8 in), they metamorphose into elvers and migrate upriver. Years later, as adult eels, these cool animals will get the call to make the long, hard journey to the sea to produce another generation of extremely flat leptocephali.
20. Sparkliest animal
Name: Japanese firefly squid, Watasenia scintillans.
Ability: putting on a mass underwater display of bioluminescence.
At night from March to May, Toyama Bay on the west coast of the Japanese island of Honshu lights up. The water flashes, sparkles, shimmers and glows, and the spectacle attracts visitors from all over Japan and from around the world. Toyama prefecture has even declared the bay a Special Natural Monument. What happens there is the annual spawning of the firefly squid. There are hundreds of thousands of small squid, each 4–6 cm (1.6–2.4 in) long, capable of producing light from hundreds of special light-producing patches of tissue on their skin called photophores. Animals that produce light are called bioluminescent, and Japanese firefly squid are probably the most exuberantly bioluminescent creatures on the planet.
When they’re spawning (producing eggs and sperm), the squid are undoubtedly using their lighting as a form of sexual communication, but when they’re not spawning, they have other uses for it. These interesting animals spend most of the year out in the open sea, either in the Pacific or the Sea of Japan. During the day they stay at a depth of 200–600 m (650–1, 970 ft), and at night they rise to the surface. It’s thought that they use the photophores to break up their outlines, confuse predators and possibly even lure in prey. Cephalopods (squid, octopus, cuttlefish) are very visual animals, but the firefly squid, which probably can see in color, may be the most visual of all.