Some female tardigrades reabsorb their eggs if no male fertilizes them

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.

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.

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.

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.

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.

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.

Tardigrades’ intrinsically disordered proteins may help preserve biological matter

Researchers have attempted to create more drought-resistant crops by introducing proteins that help protect tardigrades in their dehydrated tun state. The proteins’ ability to stabilize molecular degradation may allow scientists to develop refrigeration-free storage for vaccines, insulin, and blood.

Women are born with all the eggs they will ever produce in their lifetime

Girls are born with an estimated 1 million to 2 million eggs in their bodies, but around 10,000 die monthly before puberty. Scientists have not yet figured out why there's such an excessive number of eggs prior to menstruation, but they've calculated that there are roughly 300,000 to 400,000 eggs left at puberty.

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.

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.

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.

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.

A lunar probe’s crash landing may have spilled tardigrades onto the moon

In 2019, Israel’s Beresheet probe, which contained tardigrades in a cryptobiotic state, underwent a gyroscopic failure when attempting to land. If they survived the crash, the tardigrades may have spread across the lunar surface, raising ethical concerns about planetary contamination.

Ticks survived 27 years in a lab, including eight without food

Research published in 2022 set a new record for tick longevity. A group of adult African ticks that are normally found in eastern and southern Africa lived in a laboratory for 27 years, including eight without food. What's more, one of the females laid eggs at least four years after the last male died. Most ticks, on average, reportedly live for six months to three years.

Turtles' sense of direction comes from sensitivity to Earth's magnetic field and wave movement

Female sea turtles use this ability to migrate hundreds of kilometers across the ocean from their feeding grounds to the beaches where they were born to lay their eggs. Researchers have found that these turtles can reach these beaches despite ending up significantly off course as they detour away from predators or toward foraging territories.

Cold-blooded reptiles seek heat, and that behavior may help combat fungal infections

This Radiolab podcast episode takes on the idea that though our human bodies are too warm for the majority of fungal species to effectively replicate inside our bodies, that's not the case for reptiles. Yet when those species warm their bodies by basking in the sun on rocks, they can soak up heat and may also help keep fungal infections in check.

Herd behavior has been seen in 193-million-year-old dinosaur fossils

Scientists excavated eggs, juveniles, and adult remains in Patagonia, all arranged by age group. The organization into structured groups may have contributed to evolutionary success by consolidating eggs in one location to make defending them easier.

Has anyone had sex in space?

Reproduction is a basic human function, and while we've spent decades in space, no research has been done into the process. With many discussing the possibility of human-occupied bases on the moon, Mars, and more, understanding how sex works outside...

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

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

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

Menstruation, which occurs monthly, is the release of an unfertilized egg

This routine vaginal bleeding is part of a woman's hormonal cycle and occurs after an egg is released by an ovary during ovulation and isn't fertilized. Also known as periods, this monthly occurrence can cause symptoms including cramping, fatigue, and mood changes.

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.

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

Why are women more likely to suffer autoimmune diseases than men?

A majority of Americans with autoimmune diseases have more than one X chromosome, a typical marker of the female biological sex, according to a study published in February of 2024. During fetal development, cells side with one X chromosome over the other, preventing the overproduction of X-chromosome-specific proteins and shutting down the twin chromosome. This article explores how this X-chromosome inactivation can lead to autoimmune disorders by generating antibodies to the body's own tissues.

Mitochondria—only inherited from mothers in most animals—have their own DNA

Mitochondrial DNA, or mtDNA, typically takes the shape of a circle and contains genes that code for proteins essential to the production of energy-containing molecules called ATP. When mitochondria fuse, the mixing of healthy and damaged mtDNA helps alleviate the effects of mutations that may have occurred during mitochondrial division or environmental interactions.

Many parts of the body, including the testicles, have bitter, sweet, and umami receptors

Taste receptors—the tiny cells that report the chemical makeup of external stimuli to the brain—in the testicles don't "taste" in the same way as the gustatory ones you use to determine if there's enough sugar in your tea. Research suggests that these "teste" receptors can sense bitter, sweet, and umami compounds and use that chemical input to control physiological processes or (literally) change direction. (Some users may experience a paywall.)

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

Extremely rarely, there can be twins with different dads—but fewer than 20 such cases are documented worldwide

The non-identical twins, who would also be half-siblings, result from a rare biological phenomenon called heteropaternal superfecundation. Britain's first known twins with different dads, featured in this article, learned of each other's existence in recent years, when they were both 45. They discovered each other after taking DNA tests from Ancestry, a genealogy company.

HFMD can survive on surfaces for days at a time

That's why the virus can be transmitted via fomites—surfaces that have virus on them like doorknobs, kids toys, etc. These viruses are resilient—they are often even resistant to freezing (and are frequently stored at freezing temperatures in lab settings).

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Tattoos remain visible on your skin thanks to immune cells called macrophages

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Apollo astronauts left items in the moon's 'toss zone,' including golf balls, family photos, and bags of human waste, to make room for lunar rocks.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Georgia O'Keeffe's flower paintings are often assumed to be sexual, though the artist claimed she was simply interested in highlighting the beauty of flowers that most people neglect

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

Fast-casual restaurant Chili's is experiencing a resurgence, with its parent company recently reporting a nearly 32% increase in sales, thanks to passionate Gen Z fans on TikTok.

Brandi Chastain, the star of the 1999 US victory over China in the 1999 Women's World Cup, was a last-second choice to take the penalty kick that sealed the victory.