The Turritopsis dohrnii jellyfish can reverse its life cycle

One jellyfish species is biologically immortal

Turritopsis dohrnii is a type of jellyfish that can revert back to a juvenile stage after reaching sexual maturity, theoretically allowing it to stay alive for good. But that's a tough sell in a world full of predators. See this list of some of the longest-living species on Earth.

Meet siphonophores, breathtaking jellyfish-like organisms

Siphonophores are colonial jelly-like creatures made up of specialized segments that work together as one. They're fairly unknown despite being a significant sea predator. Sink into their strange beauty with this video.

Tardigrades can survive in a dehydrated state for decades

Despite being known as water bears, these microscopic creatures can shut down their metabolism when entering cryptobiosis, squeezing more than 95% of the water from their bodies. In this tun state, tardigrades can even survive the vacuum of space.

Can humans delay or reverse old age?

We're not sure yet. Researchers at the University of California San Francisco are studying why some conditions and behaviors, such as low-oxygen environments and exercise, benefit the aging process, hoping to reveal potential health applications. Some of this research focuses on klotho, a naturally occurring age-regulating hormone named after the Greek Fate Clotho. Animal studies on klotho brain injections found subjects had improved memory recall and age-related degeneration resistance.

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.

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.

Ticks are extremely hard to kill

These arachnids can transmit more than a dozen diseases to humans, and they're very resilient: Some can survive extreme heat and cold, live for years without a blood meal, and even survive multiple days underwater.

Oxygen and nutrients are circulated in tardigrade bodies through physical movement

Rather than having a circulatory system, oxygen is directly absorbed through their skin and spreads through a fluid called hemolymph as tardigrades crawl. When molting to grow, they shed their outer skin and stylets—sharp mouth parts used to pierce prey—which are regrown in their salivary glands.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

The Amazon molly is an all-female organism that has been cloning itself for 100,000 years without accumulating harmful mutations.

To survive underwater hibernation, some freshwater turtles perform cloacal breathing—blood vessels absorb dissolved oxygen from water drawn into the organism's cloaca, or rear orifice.

Can butterflies remember being caterpillars?

All holomatabolous insects like butterflies, bees, and moths undergo complete metamorphosis via a pupal stage. Inside the pupa, the insect breaks down into a goop of the basic elements of life like amino acids and proteins, out of which the adult stage of the insect grows. Despite this radical transformation, scientists theorize some of these insects retain what they call memories of their pre-pupa stage. Watch this video to learn more.

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.

Research has found that when their symbiotic algae are not producing oxygen via photosynthesis, corals twirl hairlike structures to circulate water and draw oxygen into their outer tissues.

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

Extreme temperature resilience appears to be temporary for tardigrades

Although often considered indestructible, scientists observed these creatures could endure temperatures near 150°C for only a few minutes in their tun state. Outside this state, only half the samples in a Danish study survived 37.1 degrees Celsius (98 degrees Fahrenheit) for 24 hours, making tardigrades extremotolerant rather than extremophiles.

Divers capture a blanket octopus unveiling her billowing membrane

In a short clip captured during a blackwater night dive in the Lembeh Strait, a blanket octopus unfolds and displays a colorful web multiple times its original size. The aquatic animal’s iridescent body and tentacles glow against the nighttime...

Fossils suggest tardigrades developed cryptobiosis more than 180 million years ago

As of 2024, three tardigrade fossils have been discovered, all preserved in amber. Analysis suggests different species of the organism existed over 500 million years ago, when marine heterotardigrades and freshwater terrestrial eutardigrades diverged. (Some readers may experience a paywall.)

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.

Tardigrades typically live between 3 and 30 months

While avoiding predators, including other tardigrades, nematodes, snails, mites and some fungi, these organisms feed on decaying plant matter and cellular fluid, which they access by puncturing cell walls with their stylets—spear-like structures within their mouths.

About 1,500 species of tardigrades have been identified by their unique physiology

Freshwater-bound eutardigrades live on mosses and lichens and are distinguished by variations in the shape and number of claws at the end of their legs. Marine heterotardigrades, which live on algae and deep-sea sediments, have been observed to possess feathers, inflatable appendages, and flagpole-like tails.

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

Acetabularia jalakanyakae is one of the largest known single-celled organisms and is nicknamed the 'mermaid's wineglass' for its umbrella-shaped cap.

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

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

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.

Through coral IVF, researchers have collected coral eggs and sperm from healthy reefs, grown baby corals in lab pools, and then released them to help repopulate damaged or lost reefs.

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.

Some female tardigrades reabsorb their eggs if no male fertilizes them

The eggs are laid in skin that has detached after molting. These species undergo sexual reproduction, but others reproduce asexually, with females producing clones from unfertilized eggs. Some hermaphrodite species have both male and female reproductive organs and can self-fertilize.

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.

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.

Europa's deep ocean may hold the conditions needed to support alien life

Beneath its frozen crust, Europa hides a salty ocean heated by tidal forces from Jupiter. This environment may resemble Earth's deep-sea hydrothermal vents and have allowed for the development of life over billions of years.

The 10 most amazing deep sea creatures

In this video, researchers from the world-renowned Monterey Bay Aquarium discuss the most fascinating deep sea creatures, and how they developed some of their strangest features.

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.

Blood has evolved many times over hundreds of millions of years, resulting in different blood colors and compositions—and there are even some organisms that don't need blood at all.

Why no aquarium has a great white shark

Historically, great white sharks die very quickly in captivity—with the exception of the Monterey Bay Aquarium's successful attempt in 2004. The aquarium held a four-year-old great white for six months. Before that, the longest stint was 16 days. The creatures can only breathe if they are moving forward, making survival difficult in a small tank.

Inside Australia's National Sea Simulator, scientists are cross-breeding coral species and using CRISPR to genetically engineer heat-resistant corals to withstand warming reefs worldwide.

Watch a time-lapse of staghorn coral polyps—a type of hard coral—over several weeks in an aquarium, slowly forming the foundational component of a coral reef.

Coral reefs are built by thousands of coral polyps—tiny animals whose mouths both consume food and expel waste.

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.

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.

While nearly all fish are cold-blooded—their body temperatures match their surroundings—the opah, or moonfish, is fully warm-blooded, with a body temperature about 5 degrees Celsius (9 degrees Fahrenheit) warmer than its environment.

Although consuming saltwater can dehydrate and kill organisms, some fish survive by using specialized gills that leach excess salt from their bodies back into the surrounding water.

The halting of human bone growth helps manage heat produced from metabolism

While fish, amphibians and reptiles get bigger throughout their lives until they die, their slower metabolisms allow their bodies to regulate the resulting smaller temperature increases. In humans, hormones triggered during puberty harden growth plates, ending bone lengthening.

In 1842, a 'mermaid' from Fiji was put on display at a museum, drawing large crowds and fooling many. It was later discovered that the creature was created by sewing the upper body of a monkey to the lower body of a fish.

Watch this octopus win every single Escape Room challenge

Octopuses are famously intelligent, solitary creatures covered in hundreds of chemical-sensing suckers. They're also pretty fascinating pets, and even enjoy playing. The crew at OctoLab put one of its more playful mollusks into four different Escape Room-like cages to see how long it would take for it to escape. Watch this video to see the brilliant, if a bit unsettling, methods the animal uses.

Multiple new research paths may lead to slowing (or even reversing) aging

Aging has always been inevitable, but fasting, epigenetic reprogramming, and parabiosis seem to help people stay young. By studying centenarians, memory, and even the humble roundworm, scientists are looking for the genetic basis to live not just a long life, but a healthy one.

Dozens of US research projects focus on the zebrafish's ability to grow new retina cells

The small, striped minnow can repair its optic nerve in just under a week. Scientists are interested in hacking its regenerative capacity to grow new retina cells to treat human eye disorders, including macular degeneration. In 2020, the US National Eye Institute had nearly 80 projects focused on zebrafish.

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.

Why tardigrades are a model extremotolerant species rather than an extremophile

By expelling most of the water from their bodies, water bears assume a state resembling a dried-up cyst and can withstand extreme environments, such as arid deserts. But in this state and these environments, tardigrades cannot grow, reproduce, or perform other functions associated with life, unlike extremophiles like dry-loving xerophiles.