Glowing creatures have fascinated humans for centuries, lighting up deep-sea waters, dark forests, and even our back gardens.
But while bioluminescence might seem magical, it always serves a purpose. From survival tactics to attracting mates, each species that glows has a reason behind its light. Some use their glow to lure prey, while others rely on it for protection or communication. Here are just some of the fascinating species that glow in the dark — and the reasons behind their natural light show.
1. Hawaiian bobtail squid
The Hawaiian bobtail squid has a special relationship with bioluminescent bacteria, which it houses inside its body. This glow helps it blend in with moonlight shining on the water’s surface, preventing predators from spotting its shadow from below. Each night, the squid carefully adjusts its glow to match the amount of light in the sky, making it almost invisible to anything lurking beneath. By day, it buries itself in the sand to avoid detection.
2. Fireflies
One of the most famous glowing creatures, fireflies use their bioluminescence for mating. Males flash specific light patterns to attract females, who respond with flashes of their own if they’re interested. Each species has its own unique pattern, preventing mix-ups in the dark. The glowing courtship dance ensures fireflies find the right mate while creating one of nature’s most mesmerising summer displays. Their light is also extremely efficient, producing no heat—unlike artificial bulbs that waste energy as heat.
3. Anglerfish
Deep-sea anglerfish are known for their eerie glowing lure, which dangles from their heads like a fishing rod. This glow is caused by bioluminescent bacteria living inside the lure, helping the fish attract prey in the pitch-black ocean depths. Since food is scarce in the deep sea, anglerfish need an advantage to hunt. Their glowing lure tricks smaller fish into thinking they’ve found food—only to end up as dinner themselves.
4. Deep-sea dragonfish
The deep-sea dragonfish is another glowing predator, using bioluminescence to lure in prey. However, it also has a special ability—unlike most bioluminescent creatures, it can produce red light as well as blue. Since most deep-sea creatures can’t see red light, the dragonfish essentially has a private spotlight, allowing it to hunt in darkness without being detected by its prey.
5. Glowing fungi
Certain types of mushrooms, such as *Mycena chlorophos* and *Armillaria mellea*, produce a soft green glow in dark forests. Unlike animals that use their glow for hunting or mating, these fungi glow to attract insects. Insects drawn to the light help spread the fungi’s spores, aiding reproduction. Scientists believe this is the fungal equivalent of flowers attracting pollinators during the day.
6. Crystal jellies – A rainbow of bioluminescence
Crystal jellies, found off the Pacific coast of North America, produce a blue-green glow due to their bioluminescent proteins. But what makes them particularly interesting is their ability to shift colours when exposed to different light. Their unique glowing proteins, known as GFP (green fluorescent protein), have even been used in scientific research, helping scientists study cells and develop new medical treatments.
7. Firefly squid – A mesmerising ocean display
The firefly squid, found in the waters off Japan, creates dazzling light displays along the coastline during breeding season. Tiny photophores along its body produce a stunning blue glow, turning the ocean into a starry sky. This glow isn’t just for show — it helps them attract mates and confuse predators by breaking up their silhouette, making them harder to spot.
8. Bioluminescent plankton
One of the most stunning natural light shows comes from microscopic plankton called dinoflagellates, which glow when disturbed. When waves crash or boats pass through, the water lights up with an eerie blue shimmer. Scientists believe this glow serves as a defence mechanism, either startling predators or attracting bigger creatures that might eat whatever is chasing the plankton.
9. Vampire squid
Despite its spooky name, the vampire squid doesn’t suck blood—it survives in deep, oxygen-poor waters by using bioluminescence for protection. It releases a glowing cloud of mucus to distract predators, giving it time to escape. Unlike squid that eject ink, the vampire squid’s glowing mucus lingers in the water, tricking attackers into following the wrong target.
10. Atolla jellyfish
The Atolla jellyfish has one of the most dramatic uses of bioluminescence—it creates a flashing ‘burglar alarm’ effect when attacked. Instead of trying to run, it lights up in a rapid, pulsing display. This attracts bigger predators that might eat whatever is attacking the jellyfish, giving it a chance to escape while its attacker becomes the new target.
11. Motyxia millipedes
Most bioluminescent creatures live in water, but the Motyxia millipede is a rare land-dweller that glows. Found in California, these millipedes emit a soft greenish-blue light, warning predators that they’re toxic. Studies have shown that glowing millipedes are far less likely to be attacked by predators compared to non-glowing ones. This suggests their glow acts as a warning, just like bright colours do in poisonous frogs.
