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

Watch a salamander grow from fertilization to hatching

New microscopy techniques have allowed scientists to image the development of animal embryos with unprecedented detail. This six-minute time-lapse reveals the development of a salamander from initial fertilization to hatching from an egg.

Despite being multicellular and photosynthetic, organisms such as kelp and sea moss are macroalgae, not plants, because they lack specialized roots and stems to pump water.

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.

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.

Harmful algal blooms can occur in warm, nutrient-rich, stagnant waters and are often associated with the rapid reproduction of blue-green algae—a misnomer for cyanobacteria, not algae.

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

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.

Across the animal kingdom, parenting can include adults carrying their young, providing their bodies for sustenance, searching for food and shelter for their children, and separating siblings who may eat one another.

View a gallery of diatoms—algae surrounded by glass-like shells—captured via microscope.

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.

Molecules derived from algae can be found in foods such as ice cream, salad dressings, brownie mix, and gravies, as well as in products such as toothpaste, multivitamins, and egg substitutes.

The world's largest species of marine algae is giant kelp, which can grow as much as two feet per day from depths of about 100 feet up to the ocean surface.

Green algae have lived on Earth for about 1 billion years, roughly twice as long as the first plants.

As of 2026, the Great Atlantic Sargassum Belt is the world's largest macroalgal bloom, with seaweed stretching from the Caribbean to West Africa.

'Artificial embryos': The hidden steps in forming a spine

Somitogenesis is the process by which segmented body structures like vertebrae form in embryos. While the process is well understood in animals like mice or zebrafish it is difficult to study in humans. But now, researchers have created a model of somitogenesis, using pluripotent stem cells, called an axioloid.

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.

'Watermelon snow'—patches of pink, orange, and red in snow—is the result of extremophilic green algae that thrive in extremely frigid conditions and take the shape of red spheres in winter.

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.

Some organisms are composed of a single cell visible to the naked eye

By incorporating tough, cellulose-rich cell walls, rapid movement of molecules via cytoplasmic streaming, and other biological techniques, some unicellular organisms can bypass the physical limitations that restrict the size of cells. Organisms such as the Stentor coeruleus and Acetabularia can be seen without microscopes.

Scientists have collected critical minerals from ocean water using seaweed, a type of algae that leaves behind a mineral-rich powder called bio-ore after being processed into biofuels.

To prevent floating away from others while sleeping, sea otters may wrap themselves in kelp or hold paws, using physical contact to form groups known as 'rafts.'

The hormone that spreads love and helps fish share fear

Scientists consider emotions like fear and empathy to be among the oldest evolutionary behaviors observed in mammals. Yet to date, how these reactions are processed in the brain, regardless of species, is not well understood. A new study reveals how the chemical oxytocin—known as the "love hormone" in humans—helps let fish know when their friends are in danger.

The Turritopsis dohrnii jellyfish can reverse its life cycle

Discovered in the 1980s, this creature has been dubbed the "immortal jellyfish" for its ability to revert from medusa to polyp form and back, preventing it from dying of old age. However, the jellyfish remains prey to fish and turtles and is defenseless to sea slugs as a polyp.

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

Some algae have helped remove microplastics from water after being bioengineered to clump together with these contaminants, forming an easily collectible microplastic-algae sludge.

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.

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.

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.

In vitro gametogenesis: using induced stem cells to fertilize eggs

Using stem cells from skin and mouth cells could save hopeful parents time and money and spare egg donors from significant amounts of discomfort throughout the process. There are potential consequences, not just for infertility treatment, but for the ability to create customized cells of any type.

An analysis of fossilized reefs from northern Africa and Germany suggests that shallow water corals and photosynthetic algae formed the mutualistic partnership seen today between 419 and 359 million years ago.

Algae can capture carbon dioxide at rates up to 50 times faster than land-based plants and can be grown in tanks that use one-tenth the land footprint of terrestrial plants.

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

Embryonic stem cells can develop into any other cell type in the body

Embryonic stem cells emerge around five days after fertilization, during the blastocyst stage of embryonic development. At this point, the embryo consists of about 100 to 150 cells and forms a hollow structure, and these cells are the ultimate source of all other cell types during fetal development.

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.

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.

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.

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.

How the heart achieves its first beat

Scientists observed zebrafish embryos as they grew and isolated the several-second-long initial heartbeats to better understand this crucial moment in every heart's life. The zebrafish's heart starts beating 20 hours into their existence. Each heart cell activates electrically at random, without rhythm. As these cells mature, they become more sensitive to electrical charges; as they all fire, a rhythm is established and a pulse is born.

As part of the up to 15 pounds of seafood they consume daily, sea otters eat urchins that feed on kelp forests—sources of shelter and food to over 800 species—thereby making the marine mammal a keystone species.

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.

The term 'symbiosis' was coined during the study of lichens—composite organisms in which algae or cyanobacteria partner with a fungus, alongside bacteria.

What a tiny marine worm can tell us about our brains

Meet the amphioxus, a small eel-like animal that has a lot to teach us about brain evolution. The genetic roots of our brains can be seen in these unusual creatures. This three-minute educational video focuses on the evolutionary history of the human brain through these odd little critters with a 500-million-year-old history.

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.

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.

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

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.

Astronauts on the International Space Station have tested an algae-powered bioreactor that converts carbon dioxide, water, and light into oxygen and edible, protein-rich biomass.

View an illustrative journey of sperm cells navigating toward fertilization

In this series of comic-style panels, a "fellowship" of sperm cells travels through fictionalized versions of reproductive anatomy on their way to an egg cell. Each panel includes informative commentary on each step of the adventure, with research insights provided by a reproductive biologist, a biomedical scientist, and an andrologist.

'Cells Making Cells': 'Science Sam' discusses the potential of stem cells

In this episode of the Ologies podcast, host Alie Ward picks the brain of science communicator Samantha Yammine—whose PhD work focused on neural stem cells. The conversation covers everything from the earliest days of stem cell research to what the future of stem cell therapies may look like.