News:

Actually sport it is a narrative

Main Menu

Intriguing Idea About the Evolution of Tardigrades (Water Bears)

Started by Recusant, February 04, 2016, 11:01:10 PM

Previous topic - Next topic

Recusant

These tiny animals are really interesting, and some might even say a bit charismatic.  ;)


A recent study has apparently shown that tardigrades are in a way mostly head, with very little (if any) body: "Tardigrades Are One Giant Head" | Discover

QuoteNo one would argue that tardigrades got stiffed in the weirdness department. These teensy animals, also called water bears, look roly-poly under a microscope. Less than a millimeter long, they can survive extremes of heat, cold, pressure, and radiation that are deadly to most other lifeforms. Under duress, a tardigrade may curl itself into a dried-up ball called a tun, then stay in a state of suspended animation for years before returning to life. Now, researchers poring over the animal's genes have found another oddity. The tardigrade, they say, is essentially one giant head.

Frank Smith, who's a postdoc in Bob Goldstein's lab at the University of North Carolina, Chapel Hill, and their colleagues studied the evolution of tardigrades by looking at their genes. Specifically, they looked at bits of DNA called "Hox genes." These are master controllers that organize an animal's body. During development, Hox genes make sure all the parts end up where they're supposed to be. Mutations in Hox genes can cause unsettling problems like, say, legs growing out of the head.

[. . .]

What emerged was a kind of whodunnit. The researchers saw that as tardigrades evolved from the ancestors they shared with arthropods, four or five of their Hox genes had simply disappeared.

Next, Smith and his colleagues asked what exactly the surviving Hox genes were doing in the tardigrade. Looking at where those genes switch on during the tardigrade's development, they saw a pattern "nearly identical" to how those genes are turned on in an arthropod's head, Smith says. In other words, most of a tardigrade's body is equivalent to just the head of an arthropod.

[Continues . . .]

In the cladogram below, there's a hint that the tardigrades may be fairly closely related to Facivermis, which had all its legs at or near its head.

"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Icarus

That is one strange looking creature bug thing.  Reminds me of some of the strange fossils in the Burgess shale. 

The day, in Genesis, when god made all the earths life forms, near the end, he was obviously becoming fatigued, or maybe high on some snort. Obviously a little bit confused when he got around to building the tartigrade, dinimichus, nectocarus, opabinia, and a shitload of other mysterious objects.

Tank

If religions were TV channels atheism is turning the TV off.
"Religion is a culture of faith; science is a culture of doubt." ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett
Remember, your inability to grasp science is not a valid argument against it.

xSilverPhinx

#3
Apparently their DNA is radiation-proof, to an extent.


These little creatures never cease to amaze me.  8)
I am what survives if it's slain - Zack Hemsey


Recusant

Thanks, xSilverphinx--that's a cool video. Nature has a brief write-up about this, and the BBC has one that goes into a bit more detail.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


joeactor


MariaEvri

I;ve heard about those things from the new cosmos series. They can survive space!
God made me an atheist, who are you to question his wisdom!
www.poseidonsimons.com

Recusant

"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

In Japan, a researcher has discovered new species of tardigrade that will reproduce sexually in a lab environment, which is unusual.

"A Totally New Species of Tardigrade Was Just Discovered in a Japanese Carpark" | Science Alert

QuoteThey're the weirdest organisms known to science: unkillable critters that can turn into glass and survive the cold vacuum of space.

But sometimes tardigrades just want to take a breather, you know? Chill for a bit in more comfortable surroundings. Which is how scientists discovered a whole new species of them living in moss on the concrete surface of a Japanese carpark.

Bioscientist Kazuharu Arakawa from Keio University was renting an apartment in the city of Tsuruoka when he scooped up a sample of moss from the building's parking lot for later analysis.

It's not as crazy as it sounds.

Tardigrades – aka water bears and moss piglets – commonly dwell in mosses, lichens, and leaf litter, so there was a chance he could get lucky.

And he did, with examination in the lab revealing 10 of the microscopic metazoans living in the sample, who were extracted and transferred into culture in five separate pairs.

One of these pairs proliferated in their dish, with subsequent microscopic and genomic analysis revealing a new species of tardigrade – Macrobiotus shonaicus – belonging to the group Macrobiotus hufelandi.

What differentiates M. shonaicus is its eggs, which have a solid surface and flexible filaments protruding outwards, similar to those of two other recently described species, M. paulinae from Africa and M. polypiformis from South America.

[. . .]

Something else that sets M. shonaicus apart is its diet. To cultivate their cultures, the researchers fed the organisms algae, but most Macrobiotidae species are carnivorous, feeding on rotifers.

There's also the question of sex.

"M. shonaicus has two sexes, where other tardigrades that are culturable in labs have been mostly parthenogenetic (females reproduce by themselves without male population)," Arakawa says.

"So it is an ideal model to study the sexual reproduction machinery and behaviours of tardigrades."

[Continues . . .]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

Trials and tribulation for some water bears. I'll just say that I'm in favor of the practice of test to destruction in the field of engineering. I look askance at its use in biology despite the fact that it may be necessary in at least some cases.  :sherlock3:


"High temperatures due to global warming will be dramatic even for tardigrades" | ScienceDaily

QuoteGlobal warming, a major aspect of climate change, is already causing a wide range of negative impacts on many habitats of our planet. It is thus of the utmost importance to understand how rising temperatures may affect animal health and welfare.

A research group from Department of Biology, University of Copenhagen has just shown that tardigrades are very vulnerable to long-term high temperature exposures. The tiny animals, in their desiccated state, are best known for their extraordinary tolerance to extreme environments.

In a study published recently in Scientific Reports, Ricardo Neves and Nadja Møbjerg and colleagues at Department of Biology, University of Copenhagen present results on the tolerance to high temperatures of a tardigrade species.

[. . .]

"The specimens used in this study were obtained from roof gutters of a house located in Nivå, Denmark. We evaluated the effect of exposures to high temperature in active and desiccated tardigrades, and we also investigated the effect of a brief acclimation period on active animals," explains postdoc Ricardo Neves.

Rather surprisingly the researchers estimated that for non-acclimated active tardigrades the median lethal temperature is 37.1°C, though a short acclimation periods leads to a small but significant increase of the median lethal temperature to 37.6°C. Interestingly, this temperature is not far from the currently measured maximum temperature in Denmark, i.e. 36.4°C. As for the desiccated specimens, the authors observed that the estimated 50% mortality temperature is 82.7°C following 1 hour exposures, though a significant decrease to 63.1°C following 24 hour exposures was registered.

[. . .]

"From this study, we can conclude that active tardigrades are vulnerable to high temperatures, though it seems that these critters would be able to acclimatize to increasing temperatures in their natural habitat. Desiccated tardigrades are much more resilient and can endure temperatures much higher than those endured by active tardigrades. However, exposure-time is clearly a limiting factor that constrains their tolerance to high temperatures," says Ricardo Neves.

Indeed, although tardigrades are able to tolerate a diverse set of severe environmental conditions, their endurance to high temperatures is noticeably limited and this might actually be the Achilles heel of these otherwise super-resistant animals.

[Link to full article.]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

Further discoveries about these intriguing animals. . . .

"Scientists finally figure out why the water bear is nearly indestructible" | Big Think

QuoteThe tardigrade, also known as the moss piglet or water bear, is a bizarre, microscopic creature that looks like something out of a Disney nightmare scene: strange but not particularly threatening. The pudgy, eight-legged, water-borne creature appears to be perpetually puckering. It's the farthest thing from what you'd expect an unstoppable organism to look like.

Yet, water bears can withstand even the vacuum of space, as one experiment showed. A sort of microscopic Rasputin, tardigrades have be frozen, boiled, exposed to extreme doses of radiation, and remarkably still survive. How they do this has been a mystery to science, until now.

Being a water-borne creature, scientists in this experiment examined how it survived desiccation, or being completely dried out. When it senses an oncoming dry period, the critter brings its head and limbs into its exoskeleton, making itself into a tiny ball. It'll stay that way, unmoving, until it's reintroduced into water.

It's this amazing ability that piqued Thomas Boothby's interest. He's a researcher at the University of North Carolina, Chapel Hill. Boothby told TheNew York Times, "They can remain like that in a dry state for years, even decades, and when you put them back in water, they revive within hours." After that, "They are running around again, they are eating, they are reproducing like nothing happened."

Originally, it was thought that the water bear employed a sugar called trehalose to shield its cells from damage. Brine shrimp (sea monkeys) and nematode worms use this sugar to protect against desiccation, through a process called anhydrobiosis. Those organisms produce enough of the sugar to make it 20% of their body weight.

Not the water bear. Trehalose only takes up about 2% of its entire system, when it's in stasis. Though employing a sugar to preserve one's body sounds strange, the newly discovered process that the water bear goes through is even more bizarre. It turns itself into glass.


[Continues . . .]

The paper is open access:

"Tardigrades Use Intrinsically Disordered Proteins to Survive Desiccation" | Molecular Cell

QuoteAbstract:

Tardigrades are microscopic animals that survive a remarkable array of stresses, including desiccation. How tardigrades survive desiccation has remained a mystery for more than 250 years. Trehalose, a disaccharide essential for several organisms to survive drying, is detected at low levels or not at all in some tardigrade species, indicating that tardigrades possess potentially novel mechanisms for surviving desiccation.

Here we show that tardigrade-specific intrinsically disordered proteins (TDPs) are essential for desiccation tolerance. TDP genes are constitutively expressed at high levels or induced during desiccation in multiple tardigrade species. TDPs are required for tardigrade desiccation tolerance, and these genes are sufficient to increase desiccation tolerance when expressed in heterologous systems.

TDPs form non-crystalline amorphous solids (vitrify) upon desiccation, and this vitrified state mirrors their protective capabilities. Our study identifies TDPs as functional mediators of tardigrade desiccation tolerance, expanding our knowledge of the roles and diversity of disordered proteins involved in stress tolerance.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Tank

Interesting. I didn't follow the Youtube link at the end  ;D
If religions were TV channels atheism is turning the TV off.
"Religion is a culture of faith; science is a culture of doubt." ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett
Remember, your inability to grasp science is not a valid argument against it.

Recusant

Continuing on the tardigrade beat...

"A New Clue Into How 'Water Bears' Evolved to Survive the Literal Vacuum of Space" | The Daily Beast

QuoteTardigrades are some of the most compelling organisms to have ever evolved on Earth. Also known as water bears, these 1-millimeter long eight-legged creatures have been known to survive the vacuum of space, withstand boiling water for at least an hour, endure high amounts of radiation, and make it through unscathed from some of the most extreme colds imaginable. As a result, tardigrades have managed to find a home on nearly every place on the planet.

How did such an organism evolve? Scientists have been trying to answer that question for a long time now, with few clues. Now, a team of Korean and Chinese researchers believe they have some insight into how tardigrades developed into the hardiest animals ever.

Tardigrades are descended from an extinct organism known as lobopodians, which lived on the planet during the Cambrian Period (which lasted from roughly 541 million years ago to 485.4 million years ago). Lobopodians themselves are an informal group of ancient marine worms with several stubby legs that lived in the ocean. Up until now, however, we've never been able to drill down exactly what groups of lobopodians today's tardigrades may descend from.

The new findings, published this week in PNAS, are the result of an analysis of 79 different subcategories of lobopodians, including 40 species of tardigrades. The new analysis found the likely ancestors of two classes of tardigrade species currently alive today, and suggest that a group of Cambrian lobopodians called luolishaniids are the most recent Cambrian ancestors of water bears. In the intervening hundreds of millions of years, it looks like tardigrades evolved into animals with shorter limbs and fewer trunk segments, developing into organisms with more miniaturized bodies.

While the study is really more of a pure science finding to fill the gaps in tardigrade evolution, they aren't without more practical implications. Tardigrades have learned to survive by essentially hitting pause on their metabolic processes until they are returned to safer conditions—something that had to have been learned over time, in the species' predecessors. They're also able to make proteins that do not degrade in what would normally be considered extreme environments—another quality that needed to have been learned over time. If we're able to pinpoint when these traits were acquired, then we may be able to do a better job of pinpointing what kinds of genes are responsible.

And given the advent of gene-editing technologies like CRISPR, that knowledge could allow us to artificially emulate those qualities in other organisms, and even ourselves.

[Continues . . .]

The paper is behind a paywall.

QuoteAbstract:

Phylum Tardigrada (water bears), well known for their cryptobiosis, includes small invertebrates with four paired limbs and is divided into two classes: Eutardigrada and Heterotardigrada. The evolutionary origin of Tardigrada is known to lie within the lobopodians, which are extinct soft-bodied worms with lobopodous ["blunt-footed"] limbs mostly discovered at sites of exceptionally well-preserved fossils. Contrary to their closest relatives, onychophorans and euarthropods, the origin of morphological characters of tardigrades remains unclear, and detailed comparison with the lobopodians has not been well explored.

Here, we present detailed morphological comparison between tardigrades and Cambrian lobopodians, with a phylogenetic analysis encompassing most of the lobopodians and three panarthropod phyla. The results indicate that the ancestral tardigrades likely had a Cambrian lobopodian–like morphology and shared most recent ancestry with the luolishaniids. Internal relationships within Tardigrada indicate that the ancestral tardigrade had a vermiform body shape without segmental plates, but possessed cuticular structures surrounding the mouth opening, and lobopodous legs terminating with claws, but without digits. This finding is in contrast to the long-standing stygarctid-like ancestor hypothesis. The highly compact and miniaturized body plan of tardigrades evolved after the tardigrade lineage diverged from an ancient shared ancestor with the luolishaniids.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Asmodean

If there be life on "long-dead" planets like Mars, I suspect it's something like them 'grades. As many legs as an spider, looking like a alien hippo and able to out-survive a roach. Fascinating creatures. :smilenod:
Quote from: Ecurb Noselrub on July 25, 2013, 08:18:52 PM
In Asmo's grey lump,
wrath and dark clouds gather force.
Luxembourg trembles.