Tardigrades | Gentle Facts For Sleep
Drift off with calm bedtime reading that supports sleep and eases insomnia as we gently explore the remarkable world of tardigrades. This calm bedtime reading for sleep and insomnia offers a peaceful way to unwind while your mind settles into rest. In this episode, Benjamin shares simple, fascinating facts about these tiny “water bears,” letting you learn something new while relaxing deeply. His steady, soothing cadence creates a peaceful atmosphere without whispering, just calm, educational storytelling designed for bedtime. It’s ideal for restless nights, stress, anxiety, and anyone looking for a gentle routine that supports better sleep and relief from insomnia. Press play, get comfortable, and let your thoughts drift as the facts slowly fade into the background. Happy sleeping!
Transcript
Welcome to the I Can't Sleep Podcast,
Where I help you drift off one fact at a time.
I'm your host,
Benjamin Boster,
And today's episode is about tardigrades.
Tonight's topic is a sponsored episode for Toby.
Tardigrades,
Also known as water bears or moss piglets,
Are a phylum of eight-legged segmented micro-animals.
They were first described by the German zoologist Johann August Ephraim Goetze in 1773,
Who called them Kleine Wasserbär,
Little Water Bear.
In 1776,
The Italian biologist Lazzaro Spallanzani named them tardigrada,
Which means slow walkers.
Tardigrades live in diverse regions of Earth's biosphere,
Mountaintops,
The deep sea,
Tropical rainforests,
And the Antarctic.
They are among the most resilient animals known,
With individual species able to survive severe conditions,
Such as exposure to extreme temperatures,
Extreme pressures both high and low,
Air deprivation,
Radiation,
Dehydration,
And starvation,
That would quickly kill most other forms of life.
Tardigrades have survived exposure to outer space.
There are about 1,
500 known species in the phylum tardigrada,
A part of the superphylum Ectisosazoa.
The earliest known fossil is from the Cambrian,
Some 500 million years ago.
They lack several of the Hox genes found in arthropods,
And the middle region of the body corresponding to an arthropod's thorax and abdomen.
Instead,
Most of their body is homologous to an arthropod's head.
Tardigrades are usually about 0.
5 mm long when fully grown.
They are short and plump,
With four pairs of legs,
Each ending in claws,
Usually four to eight,
Or sticky pads.
Tardigrades are prevalent in mosses and lichens,
And can readily be collected and viewed under a low-power microscope,
Making them accessible to students and amateur scientists.
Their clumsy crawling and their well-known ability to survive extreme conditions have brought them into science fiction and popular culture,
Including items of clothing,
Statues,
Soft toys,
And crochet patterns.
Tardigrades have a short,
Plump body with four pairs of hollow,
Unjointed legs.
Most range from 0.
05 to 0.
5 mm in length,
Although the largest species may reach 1.
3 mm.
The body cavity is a hemocil,
An open circulatory system filled with a colorless fluid.
The body covering is a cuticle that is replaced when the animal molds.
It contains hardened proteins and chitin,
But is not calcified.
Each leg ends in one or more claws,
According to the species.
In some species,
The claws are modified as sticky pads.
In marine species,
The legs are telescopic.
There are no lungs,
Gills,
Or blood vessels,
So tardigrades rely on diffusion through the cuticle and body cavity for gas exchange.
They are made up of only about 1,
000 cells.
The tardigrade nervous system has a pair of ventral nerve cords with a pair of ganglia serving each pair of legs.
The nerve cords end near the mouth at a pair of subpharyngeal ganglia.
These are connected by paired commissures to the dorsally located cerebral ganglion,
Or brain.
Also in the head are two eye spots in the brain,
And several sensory seri and pairs of hollow antenna-like clavi,
Which may be chemoreceptors.
The tardigrade Dactylobiotus dispar can be trained by classical conditioning to curl up into the defensive tun state in response to a blue light associated with a small electric shock and aversive stimulus.
This demonstrates the tardigrades are capable of learning.
Although the body is flexible and fluid-filled,
Locomotion does not operate mainly hydrostatically.
Instead,
As in arthropods,
The muscles,
Sometimes just one or a few cells,
Work in antagonistic pairs that make each leg step backwards and forwards.
There are also some flexors that work against hydrostatic pressure of a hemocyle.
The claws help to stop the legs sliding during walking,
And are used for gripping.
Tardigrades feed by sucking animal or plant cell fluids,
Or on detritus.
A pair of stylets pierce the prey.
The pharynx muscles then pump the fluids from the prey into the gut.
A pair of salivary glands secrete a digestive fluid into the mouth,
And produce replacement stylets each time the animal molts.
Tardigrades,
As a group,
Are cosmopolitan,
Living in many environments on land,
In freshwater,
And in the sea.
Their eggs in resistant life cycle stages,
Cystus and tons,
Are small and durable enough to enable long-distance transport,
Whether on the feet of other animals or by the wind.
Individual species have more specialized distributions,
Many being both regional and limited to a single type of habitat,
Such as mountains.
Some species have wide distributions.
For instance,
Achinicus lineatus is pantropical.
Halobiotus is restricted to cold,
Halarctic seas.
Species such as Borealobius and Achinicus lapinecus have a discontinuous distribution,
Being both polar and on tall mountains.
This could be a result of long-distance transport by the wind,
Or the remains of an ancient geographic range when the climate was colder.
A small percentage of species may be cosmopolitan.
The majority of species live in damp habitats,
Such as on lichens,
Liverworts,
And mosses,
And directly in soil and leaf litter.
In freshwater and the sea,
They live on and in the bottom,
Such as in between particles or around seaweeds.
More specialized habitats include hot springs and as parasites or commensals of marine invertebrates.
In soil,
There can be as many as 300,
000 per square meter.
On mosses,
They can reach a density of over 2 million per square meter.
Tardigrades are not considered universally extremophilic because they are not adapted to exploit many of the extreme conditions that their environmental tolerance has been measured in,
Only to endure them.
This means that their chances of dying increase the longer they are exposed to these extreme environments.
Whereas true extremophiles thrive there.
Tardigrades are capable of suspending their metabolism,
Going into a state of cryptobiosis.
Terrestrial and freshwater tardigrades are able to tolerate long periods when water is not available,
Such as when the moss or pond they are living in dries out.
Tardigrades are capable of drying their legs in and forming a desiccated cyst,
The cryptobiotic tun state,
Where no metabolic activity takes place.
In this state,
They can go without food or water for several years.
Further in that state,
They become highly resistant to environmental stresses,
Including temperatures from as low as negative 272 degrees Celsius to as much as 149 degrees Celsius,
At least for short periods of time.
Lack of oxygen,
Vacuum,
Ionizing radiation,
And high pressure.
Marine tardigrades alternate each year between an active summer morph and a hibernating winter morph that can resist freezing and low salinity,
But which remains active throughout.
Reproduction,
However,
Takes place only in the summer morph.
Tardigrades can survive impacts up to about 900 meters per second and momentary shock pressures up to about 1.
14 gigapascals.
Tardigrades have survived exposure to space.
In 2007,
Dehydrated tardigrades were taken on the Photon M3 mission and exposed to vacuum,
Or to both vacuum and solar ultraviolet for 10 days.
Back on Earth,
More than 68% of the subjects protected from ultraviolet were reanimated by rehydration,
And many produced viable embryos.
In contrast,
Hydrated samples exposed to vacuum and solar ultraviolet survived poorly,
With only three subjects surviving.
The space vacuum did not much effect egg laying,
Whereas UV radiation reduced egg laying.
In 2011,
Tardigrades went on the International Space Station STS-134,
Showing that they could survive microgravity and cosmic radiation,
And should be suitable model organisms.
In 2019,
A capsule containing tardigrades in a cryptobiotic state was on board the Israeli lunar lander Bereshit,
Which crashed on the moon.
Tardigrades' ability to stay desiccated for long periods of time was thought to depend on high levels of the sugar trellos,
Common in organisms that survive desiccation.
However,
Tardigrades do not synthesize enough trellos for this function.
Instead,
Tardigrades produce intrinsically disordered proteins in response to desiccation.
Three of these are specific to tardigrades,
And have been called tardigrade-specific proteins.
These may protect membranes from damage by associating with the polar heads of lipid molecules.
The proteins may also form a gas-like matrix that protects cytoplasm from damage during desiccation.
Anhydrobiosis in response to desiccation has a complex molecular basis.
Tardigrades possess a cold shock protein.
Maria Camillari and colleagues propose that this may serve as a RNA chaperone involved in regulation of translation following freezing.
Tardigrade DNA is protected from radiation by the Dsup damage suppressor protein.
In 1773,
Johann August Ephraim Goetze named the tardigrade Kleine Wasserbär,
Meaning little water bear in German.
Today Germans often call them Bärtierchen,
Little bear animal.
The name water bear comes from the way they walk,
Reminiscent of a bear's gait.
The name tardigradum means slow walker,
And was given by Lazzaro Spallanzani in 1776.
In 1834,
C.
A.
S.
Schultz gave the first formal description of a tardigrade,
Macrobiotus effulandi,
In a work subtitled,
A New Animal from the Crustacean Class,
Capable of Reviving After Prolonged Asphyxia and Dryness.
Ferdinand Richters worked on the taxonomy of tardigrades from 1900 to 1913,
With studies of Nordic,
Arctic,
Marine,
And South American species.
Tardigrade fossils are rare.
The only known specimens are those from mid-Cambrian deposits in Siberia.
And a few specimens in amber from the Cretaceous of North America and the Neogene of the Dominican Republic.
The Siberian fossils differ from living tardigrades in several ways.
They have three pairs of legs rather than four.
They have a simplified head morphology.
And they have no posterior head appendages.
But they share with modern tardigrades their columnar cuticle construction.
Scientists think they represent a stem group of living tardigrades.
Possibly the first time that tardigrades appear in non-scientific literature is in the short story,
Basibia.
By the geologist and explorer Douglas Mawson.
Published in the 1908 book Aurora Australis and printed in the Antarctic,
It deals with an expedition to the South Pole,
Where the team encounters giant mushrooms and arthropods.
The team watches a giant tardigrade fighting a similarly enormous rotifer.
Another giant water bear bites a man's toe,
Rendering him comatose for half an hour with its anesthetic bite.
Finally,
A four-foot-long tardigrade,
Waking from hibernation,
Scares the narrator from his sleep and he realizes it was all a dream.
Tardigrades are common in mosses and lichens on walls and roofs,
And can readily be collected and viewed under a low-power microscope.
If they are dry,
They can be reanimated on a microscope slide by adding a little water,
Making them accessible to beginning students and amateur scientists.
Current biology attributed their popularity to their clumsy crawling,
Which is about as adorable as can be.
The zoologist James F.
Fleming and Katsuhiro Arakawa called them a charismatic phylum.
They have been famous for their ability to survive life-stopping events,
Which has been dried out since Spallanzini first resuscitated them from some dry sediment in a gutter in the 18th century.
In 2015,
The astrophysicist and science communicator Neil deGrasse Tyson described Earth as the planet of the tardigrades,
And they were nominated for the American Name Society's Name of the Year award.
Live Science notes that they are popular enough to appear on merchandise like clothes,
Earrings,
And keychains,
With crochet patterns for people to make their own tardigrade.
The Dutch artist Arno Conin created statues for St.
Eusebius' church Arnhem of microscopic organisms,
Including a tardigrade and a coronavirus.
Milnesium tardigradum was voted the winner of the Guardians 2025 Invertebrate of the Year competition from a short list of 10.
The article describing the conclusion of the contest stated that the species had endured all five previous planetary extinction events.
The tardigrades' traits,
Including their ability to survive extreme conditions,
Have earned them a place in science fiction and other pop culture.
The musician Cosmo Sheldrake imagines himself as a robust tardigrade in his 2015 tardigrade song.
He sings,
If I were a tardigrade,
Pressure wouldn't squash me,
And fire couldn't burn.
I can live life in vacuums for years with no drink.
The biologists Mark Blackster and Arakawa Katsuharu describe tardigrades' transition to science fiction and fantasy as resulting in rare but entertaining walk-on parts.
They note that in the 2015 sci-fi horror film Harbinger Down,
The protagonists have to deal with tardigrades that have mutated through Cold War experiments into intelligent and deadly shapeshifters.
In the 2017 Star Trek Discovery,
The alien Ripper creature is a huge but generally recognizable version of a terrestrial tardigrade.
The protagonist,
The xenoanthropologist Michael Burnham,
Explains that the Ripper can incorporate foreign DNA into its own genome via horizontal gene transfer.
When Ripper borrows DNA from the mycelium of its symbiotic fungi,
He's granted an all-axis travel pass.
The scholar of science and popular culture,
Lisa Meinecke,
In Fighting for the Future,
Essays on Star Trek Discovery,
Writes that the animal shares some of the real tardigrade's characteristics,
Including its physical resilience to extreme environmental stresses.
She adds that while taking on fungal DNA is ostensibly grounded in science,
It equally carries a mystical impetus of what the French philosophers Deleuze and Quattari call a becoming,
An entanglement of species that changes those involved and ties together all life.
The border of that symbiosis is the outsider or anomalous,
Which stabilizes the system and embodies its future possibilities.
The characters Burnham and Stamets see that the tardigrade plays this outsider role.
Microfauna,
From ancient Greek mikros,
Small,
And Latin fauna,
Animal,
Are microscopic animals and organisms that exhibit animal-like qualities and have body sizes that are usually less than 0.
1 mm.
Microfauna are represented in the animal kingdom,
E.
G.
Nematodes,
Small anthropods,
And some other heterotrophic microscopic eukaryotes.
A large amount of microfauna are soil microfauna,
Which includes eukaryotic microbes,
Rotifers,
And nematodes.
These types of animal-like eukaryotic microbes,
And true animals,
Are heterotrophic,
Largely feeding on bacteria.
However,
Some microfauna can consume other things,
Making them detritivores,
Fungivores,
Or even predators.
Microfauna are present in every habitat on Earth.
They fill essential roles as decomposers and food sources for lower trophic levels and are necessary to drive processes within larger organisms.
Many microfauna,
Such as nematodes,
Inhabit soil habitats.
Plant parasitic nematodes inhabit the roots of various plants,
While free-living nematodes live in soil-water films.
Microfauna also inhabit freshwater ecosystems.
For example,
Freshwater microfauna in Australia include rotifers,
Ostracods,
Copepods,
And cladocerans.
Rotifers are filter feeders that are usually found in freshwater and water films.
They consume a variety of things,
Including bacteria,
Algae,
Plant cells,
And organic material.
Tardigrades inhabit a variety of lichens and mosses.
They need water in these areas to allow for gas exchange and to prevent them from desiccating.
Because of this,
They are considered aquatic.
However,
They have also been found in all types of environments,
Ranging from the deep sea to dunes.
One particular example of the role of microfauna can be seen in soil,
Where they are important in the cycling of nutrients in ecosystems.
The ecological functions of the rhizosphere can be influenced by microfauna,
Specifically by nematodes and protozoa,
Which are abundant in soil.
For instance,
The carbon cycling within the soil can be affected by nematodes who will feed on the roots of plants,
Impacting the organic carbon in the soil.
Similarly,
Soil protozoa are able to release phosphorus and nitrogen into the soil and higher trophic levels by dissolving the organic material and nutrients available.
Soil microfauna can also impact microorganisms within the rhizosphere by affecting their diversity and accelerating microorganism turnover.
This happens because of the microfauna's selective grazing and their ability to influence the resources within the soil.
For example,
Protozoa can help maintain the quality of the soil by grazing on soil bacteria.
Through their grazing,
The protozoa can help maintain populations of bacteria,
Allowing the bacteria to more efficiently decompose dead organic material,
Which will improve the fertility of the soil.
Soil microfauna are capable of digesting just about any organic substance and some inorganic substances.
These organisms are often essential links in the food chain between primary producers and larger species.
For example,
Zooplankton are widespread microscopic animals and protists that feed on algae and detritus in the ocean,
Such as foraminifera.
Microfauna also aid in digestion and other processes in larger organisms.
© transcript Emily Beynon
