The tardigrade is also known as a water bear or "moss piglet."
It's rare to write about every cool science-y story that comes our way. Each day from December 25 through January 5, we'll post a science story that fell through the cracks in 2020, highlighting it in a special Twelve days of Christmas series. The physics of the tardigrade are amazing.
Is there anything the tiny tardigrade can't do? Water bears are known for their ability to survive in extreme conditions, and they are a favorite case study for scientists.
The water bear's movement resembles that of insects 500,000 times its size, according to a paper published in August in the Proceedings of the National Academy of Sciences.
A recent preprint published on the physics arXiv claims that frozen tardigrades can achieve a state of "temporary quantum entanglement" when incorporated into a superconducting qubit. It would be the first time that a living animal has achieved a quantum entangled state.
"Slow walkers"
The name "water bear" came to us from German zoologist Johann August Ephraim Goeze, who first observed the creatures in 1773 and named them kleiner Wasserbr. The Latin Tardigradum means "slow walker" and was the name given to the creatures by Lazzaro Spallanzani.
Both names were inspired by the creature's slow, lumbering movement and its odd barrel-shaped bodies with four pairs of stubby legs.
According to Jasmine Nirody, a co-author on the PNAS paper,ardigrades have a clear and robust way of moving. The locomotive strategy of insects and arthropods is similar to that of larger insects and arthropods.
"Tardigrades are an important porthole into soft-bodied, microscale locomotion, with the potential to offer insight into how to build more efficient soft microscale robots," she said. We don't know how to make an efficient small walker, or how soft-bodied things should move.
The water bears were placed on glass slides, but the tardigrades couldn't propel themselves along the surface very efficiently. They needed to be able to push off with their claws. The glass slides were replaced with gels. The microscopes and cameras that were set up in the lab were used to collect hours and hours of footage of the creatures' movements.
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Tardigrades walk in a way that is close to insects 500,000 times their size.
Nirody said that if you watch tardigrades under a light microscope, you can capture a wide range of behavior. We did not force them to do anything. Sometimes they would just want to walk around. Sometimes they would see something they liked and run towards it.
The team was surprised to learn that the water bears did not have a specific speed for each speed. Their movement was similar to that of insects and arthropods, with no change to the basic step pattern.
As the tardigrades sped up, they would transition between having five legs on the ground, four on the ground, and three on the ground, just like insects and arthropods, despite a 20-million-year evolutionary gap between them.
There are two leading hypotheses for why this might be the case. Water bears, insects, and arthropods have a common neural circuit. The organisms may have evolved this behavior on their own.
Nirody said that they have a lot to learn if there is an ancestral neural system that controls panarthropods walking. If arthropods and tardigrades converge upon this strategy independently, there is much to be said about what makes this strategy so palatable for species in different environments.
What is the tardigrade of Schroedinger?
One of the co-authors on the recent arXiv preprint said that tardigrades may be capable of unique quantum feats when in their hibernating state. One of the strangest aspects of quantum mechanics is the fact that two particles can be so close together that one can influence the other. Albert Einstein dubbed it "spooky action at a distance" because it was so counter-intuitive.
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Without quantum computers, it would be impossible. Physicists succeeded in achieving a version of the cat in the lab with the help of a record-breaking 20 qubits.
A study done in the summer of 2018 found that certain photosyntheticbacteria could become entangled with light. The conditions arise when the light in a mirrored room syncs with the light in the bacterium's photosynthetic molecule.
It has never been done with a multi-cellular organisms. The three tardigrades were collected from a roof gutter inDenmark and then frozen until they were a third of their normal size. The tardigrades were cooled even further, to just above absolute zero.
In the first season of Star Trek: Discovery, the alien "Ripper" creature who is used to "navigate" through a galactic mycelium network is described as a giant cousin of the tardigrade.
They placed each tardigrade between the two plates of the circuit. When the qubit came into contact with a frozen tardigrade, it formed a qubit-tardigrade hybrid. Verdal and his colleagues combined that hybrid to a second qubit. Several tests showed a shift in frequencies between the entangled qubits and the tardigrade. The tardigrades were revived after the experiments were over.
"While one might expect similar physical results from objects with similar composition to the tardigrade, we emphasize that the entire organisms that retain their biological function after the experiment are the most likely to be entangled," they said. The tardigrade was exposed to the most extreme and longest conditions it has ever been exposed to.
We aren't likely to see quantum computers running on tardigrades any time soon. The conclusion of Verdal et al. was met with skepticism. Ben Bruabker, a former physicist turned science writer, posted a lengthy thread on his social networking site, calling the findings into question.
This isn't meaningful in a meaningful sense. The tardigrade is not a single quantum object with a small number of degrees of freedom.
Verdal defended his team's claim.
The PNAS is published in 2021. About DOIs is 10.1073/pnas.2107289118.
