When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

Biofluorescent animals—those that absorb light, such as ultraviolet rays, and re-emit other types of light, such as neon green—include some flying squirrels, scorpions, sea turtles, and platypuses.

Bioluminescence provides organisms with a method of hunting, defense, or mating

Unlike glow sticks, bioluminescent reactions use renewable resources like oxygen and ATP. This ability allows fireflies to mate and deter predators, anglerfish to confuse and attract prey, and deep-sea shrimp to defend themselves by vomiting glowing slush.

View examples of luciferin, the light-emitting molecule behind bioluminescence

Bioluminescent marine organisms rely on various unique luciferins, including Cypridina-type luciferin in seed shrimp and chlorophyll-based dinoflagellate luciferin, to react with oxygen to produce light. These chemicals require unique catalysts to help them bind with oxygen.

View illustrations of bioluminescent functions in marine organisms

Bioluminescence can startle predators, camouflage, lure prey, confuse rivals, or facilitate mate recognition. One tactic—the burglar alarm—involves an organism releasing light to attract a larger predator to its attacker as a means of defense.

Bioluminescent organisms produce their own light through chemical reactions involving unstable, energetic molecules, while biofluorescent organisms almost immediately re-emit light shone on them, but at a different wavelength.

Massive blooms of microscopic algae called dinoflagellates produce the neon blue light seen in glowing tides.

Why 75% of ocean animals glow

About 75% of ocean creatures can make their own light. It's called bioluminescence—and it all comes down to a special chemical reaction happening inside their bodies.

Bioluminescence became common in the ocean to support survival in dark environments

Despite seeming like a rare ability in land animals and unseen in plants, bioluminescence has evolved at least 29 times across marine species, indicating its necessity for survival where hiding spots are rare and highlighting how environments provide evolutionary pressure.

Starting with red, colorful objects will appear to lose their colors the deeper they are submerged because water scatters light, reducing the amount available to reflect off objects and be observed.

View a gallery of bioluminescent organisms, including jellyfish and mushrooms

Some species produce a quick flash of light, while others glow steadily with an eerie glow, often to seek attention or in response to being disturbed. Snails, worms, fungi, and other organisms highlight that this ability evolved independently, rather than from one common ancestor.

Some corals absorb harmful ultraviolet radiation and re-emit it as visible light, thereby protecting symbiotic algae within their tissues and providing them with energy for photosynthesis.

Because it is observed in organisms that are not closely related, biofluorescence is thought to have emerged independently many times in nature—over 100 in fish alone.

Fireflies light up to provide mating signals and warnings to predators

Variations in the illumination patterns and flight paths while emitting light have been observed across firefly species. Some species instead rely on pheromones if they are primarily active during the day or have lost the ability to illuminate.

The first appearance of bioluminescence was at least 540 million years ago

After analyzing fossils, genetic data, and statistical methods, scientists believe octocorals were the first organisms to evolve light-producing abilities. As a result of independent evolution across at least 94 species, this phenomenon is connected to a diverse range of behaviors.

A look at how fish less than two inches long climb up 50-foot waterfalls

Shellears use tiny hooks on their front pectoral fins to grip rock like Velcro and take many pauses to recover energy between bursts of movement. Their pectoral girdle—an arch of bone—supports the muscle system needed for the roughly ten-hour climb.

Watch David Attenborough's documentary on bioluminescent creatures, which have been observed using light for hunting, mating, communication, and self-defense, and number in the thousands of species.

Flamingos get their pink coloring from carotenoids—pigments of yellow, orange, and red—in their food, but they cannot take on other colorations because their bodies cannot process other pigments.

Over 1 million fish, marine mammals, and invertebrate species depend on coral reefs for habitats, camouflage, and food.

Synthetic pheromones may protect coral reefs by attracting their predators

Researchers in Australia and Japan have developed these nontoxic chemicals to attract crown-of-thorns starfish, which consume corals that make up the Great Barrier Reef. As of 2026, synthetic pheromones have been shown to be effective in lab trials, and future field trials will attempt to lure starfish into areas for mass removal.

Some female fireflies mimic the signals of other species to lure in and eat them

The genus Photuris does not produce its own defensive pheromones to ward off predators, so it has developed mimicry to attract males of firefly species that do. Unsuspecting males are consumed after these chemicals—lucibufagins—are extracted.

View a gallery of animals found on abyssal plains, hydrothermal vents, seamounts, and other deep-sea habitats.

Humans have used bioluminescence as a means of military advantage

During World War I, the British Navy sank a German U-boat after spotting the blue light forming at the sides and in the wake of the boat. Jellyfish slime was applied to a Roman walking stick for nighttime guidance, while bioluminescent fungi in Indonesia fulfilled the same purpose.

Meet Cystisoma, the 7-inch crustacean with eyes for a head

In deep midwater, roughly 1,000 feet below the water's surface, completely transparent Cystisoma hide in plain sight from predators. Their retinas are splayed out thin across their disproportionately large eyes to avoid detection, and their entire bodies are transparent, difficult to see even as they are held in the palm of your hand. Learn more about the creatures here.

Solutions of bioluminescent bacteria can create FOMO-inducing living art

A 2002 exhibition at Montana State University-Bozeman placed the bacteria onto petri dishes that served as macroscopic pixels to create images. Once the bacteria finished eating all the food in the sealed dishes, the light slowly faded away, ending the exhibit.

During coral bleaching, corals sacrifice their food source and expel colorful microorganisms to protect themselves, a phenomenon that resembles an organism's immune system attacking itself.

Studying the circadian clock of a tiny swimming polar creature may help forecast polar ecosystem health

A 2025 study found that Antarctic krill, a food chain staple in the Southern Ocean, have an internal biological clock that helps regulate its swimming patterns and helps the tiny shrimp-like animals adapt to daily and seasonal environmental changes. Better understanding of how the clock and light cues interact may help scientists understand how well the species will respond to pronounced climate change in the polar region.

Take an interactive dive and see the animals that populate the oceans, from coral near the surface to shrimp-like organisms near the seafloor.

Light pollution is giving oysters insomnia

Oysters, bivalve mollusks that have light-detecting cells along their skin, can't sleep with all this artificial light. According to a 2022 study, oysters' sleep cycles are disturbed by light dimmer than that provided by the full moon. As with humans, it's possible that these bouts of insomnia could have adverse health effects and contribute to the development of disease over time.

The fish can climb walls

Scientists in Brazil captured rare footage of bumblebee catfish climbing waterfalls. How they do it is clear, but why remains a mystery.

Sea stars are invertebrates—they lack a backbone—and while most exhibit pentametric radial symmetry due to having five arms radiating from a central disk, some can possess more than 40.

Watch underwater photosynthesis make water look like champagne

In shallow waters where sunlight can reach, photosynthetic reactions absorb water and dissolved carbon dioxide, producing bubbles of oxygen at the surface of plants. As these bubbles rise to the water's surface, a fizzy appearance is created.

Blacklights can illuminate certain biological materials, including blood, teeth, and fingernails, because they contain fluorophores—molecules that visibly glow immediately after exposure to higher-energy light.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

By targeting a diverse range of sick and injured marine life, sharks—a type of predatory keystone species—help keep ocean gene pools healthy and promote biodiversity by keeping prey species in check.

View a gallery of biofluorescent animals, which contain cells that emit various colors when exposed to ultraviolet light.

Some marine life can survive the extreme pressure of the deep ocean because of specialized molecules that strengthen proteins, enzymes, and cellular membranes.

Whale falls—dead whales that have fallen to the ocean's floor—can provide enough food to spawn a local ecosystem of deep-sea organisms that lasts for decades.

Coral reefs get their colors from zooxanthellae—photosynthetic algae that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

The love lives of pygmy seahorses

Inch-long pygmy seahorses live fascinating lives in the Coral Triangle of Southeast Asia, where the tiny sea creatures thrive. They are one of the few species in the world where the male carries its progeny to term, in this case, after receiving an egg from the female, who keeps busy checking in on her two male mates, one of whom is always pregnant. Dive into the marine romance in this fascinating essay.

View a sample of the bioluminescent tree of life

This diagram shows 42 different light-producing organisms, from bacteria and fungi to worms, fish, and crustaceans. It illustrates how the ability to produce light has appeared multiple times across the tree of life, rather than stemming from a single ancestor.

Artificial lightning can improve the yield of shiitake mushroom growers

Researchers have found that shockwaves produced from lightning strikes homogenously break internal filaments called hyphae, transitioning the mushrooms from a vegetative growth to a fruiting phase. Repeated minor shocks near mushroom logs mimicked this effect.

How goldfish cause significant environmental damage when released

Researchers have found that goldfish cause "regime shifts" in habitats as they search for food in places like lake beds, kicking up sediment that muddies the water and disrupts small invertebrates. They can also outcompete native species to further destabilize existing food webs.

Chameleons change color by altering the spacing of nanocrystals under their skin, which changes what colors of light are absorbed and reflected.

View the fluorescently stained internal structures of a tardigrade

The photograph won the Olympus Global Life Science Light Microscopy Americas regional award in 2019. Using chemicals from biofluorescent organisms, the image illuminates internal structures with multiple hues in an otherwise mostly colorless organism.

View a gallery of plants made to shine using ultraviolet-induced visible fluorescence photography, in which organisms re-emit the ultraviolet light they are exposed to in vibrant, glowing colors.

The cells of spotted salamander embryos and early-stage larvae harbor algae that support embryonic development by increasing oxygen levels and removing waste.

As immobile animals, corals and the organisms that live on them have evolved a suite of chemical compounds to prevent disease and ward off predators they cannot outrun.

The deep-sea fangtooth has the largest teeth of any marine species relative to body size

From transparent fish to the heaviest worms on the planet, these seven creepy creatures lurk in the deep sea. Learn all about them and the unique traits that help them survive and hunt.

Some invasive species' populations have been controlled by turning them into cash crops that can be harvested and sold to produce useful materials.

Catfish have taste buds spread across their entire skin, making their whole body function like a tongue that can taste food several feet away.