Departing the Vacuousness
Started by Recusant, February 04, 2016, 11:01:10 PM
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 . . .]
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 . . .]
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.]
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 . . .]
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.