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Evolutionary Enigmas, Tiny Tardigrades Strut Their Superpowers

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Looking like squishy plump toys or alien invaders, take your pick, tardigrades are survivors extraordinaire. Also called water bears or moss piglets, these tiny arthropods with eight legs and eyeless faces seem wrapped in heavy survival canvas. But that’s not what gives them their invincibility. 

Tardigrades, found around the world in a wide variety of environments, amaze scientists with their ability to withstand heavy doses of radiation, heat and cold, desiccation, and even the vacuum of space. See past articles at Evolution News on tardigrades, here and here, where evolutionists were struggling to explain why any creature would evolve protections from environmental conditions it had never experienced.

Some progress has been made recently on figuring out how these tiny creatures, less than a millimeter in length, survive conditions that would freeze, fry, or zap other organisms. News from UC San Diego, complete with two delightful color pictures of tardigrades, offers a possible explanation — and it’s about a protein. Dsup, or “damage suppressor protein,” is found only in tardigrades. The researchers found out two things about Dsup: (1) it clamps onto chromatin, the protein-and-DNA structures that wind genetic material into compact structures, and (2) it provides a “protective cloud” around the chromatin, shielding it from damage by hydroxyl radicals. Hydroxyl radicals are formed when X-rays disrupt water molecules, leaving charged OH ions floating that can damage DNA. 

The news is not clear on the nature of this protective cloud, what it looks like or how it works. Live Science quotes one of the team members describing it a little bit:

“We thought, ‘Why don’t we just see if Dsup can protect DNA from hydroxyl radicals?’ And the answer is yes, it can,” [James] Kadonaga explained. High-energy Dsup has a cloud-like structure; the cloud surrounds the DNA’s chromatin envelope, blocking hydroxyl radicals and preventing them from disrupting cellular DNA, the researchers reported. [Emphasis added.]

A Partial Answer

Whatever this “cloud” looks like, or how it deflects hydroxyl radicals, it appears to give only a partial answer to the tardigrade’s robustness. Dsup deflects OH ions somehow, but how does it protect the tardigrade from extreme cold or heat, or from the vacuum of space? Surely other mechanisms are involved that can provide a complete toolkit the organism draws on for a variety of conditions, some of them never encountered in the animal’s natural environment. The authors speculate that tardigrades evolved this protein because they often encounter free radicals in their watery environments, and must survive desiccation when the water dries up. But many other small animals also face such risks without Dsup. Finding a “need” for such a protein cannot explain how it evolved. You might need a pair of wings to fly over traffic to work, but chance is not going to provide them. 

Other questions come to mind: is Dsup found in every cell of the tardigrade? Is it active on all chromatin all the time, or only when the cell is stressed? Is there a downside to its “cloud” formation? For instance, molecular machines need to access chromatin regularly; can they do it when Dsup is bound to the chromatin? Why is Dsup unique to tardigrades, if it is so beneficial? And can humans benefit from Dsup-fortified cells?

On that last question, Live Science notes that an earlier study showed that “when added to human cells, Dsup safeguards against damage from X-rays.” Dsup might be a general-purpose protector of DNA. The UC team believes that their discovery of Dsup’s “cloud” protection could help all kinds of cells survive better.

By piecing together how Dsup functions at ever-more-precise levels, scientists can then use it as a blueprint for building other types of proteins — “better versions of Dsup” — that are even more effective at protecting cells from DNA damage, Kadonaga said. These new proteins probably won’t be used to produce radiation-proof people, but they could improve the hardiness of cultured cells that are used for growing pharmaceuticals, he added.

“You can have more-durable cells, more-longer-lived cells. That might be a case for putting some form of Dsup in that cell,” he said.

Proteins, unquestionably, are highly improbable arrangements of amino acids. Uniprot shows that Dsup is a large protein, 445 amino acids long. That’s way beyond the probability of chance. Moreover, it would be useless if this protein didn’t bind to chromatin at the right time, in the right way, and in the right cooperation with other cellular functions. It will be interesting to learn more about this amazing protein, and see if it can help humans live longer.

New Relative Found in Amber

So that’s the news about moss piglets, but now there’s a mold pig. George Poinar and a colleague at Oregon State University found hundreds of tardigrade lookalikes in amber recently. “Meet the ‘mold pigs,’ a new group of invertebrates from 30 million years ago,” OSU announces. Anyone looking at the photo is bound to think it’s just another tardigrade, but surprisingly, Poinar, an expert in amber fossils, claims it is so different, he needs to classify it in a new family and class, if not a new phylum!

The several hundred individual fossils preserved in the amber shared warm, moist surroundings with pseudoscorpions, nematodes, fungi and protozoa, Poinar said.

“The large number of fossils provided additional evidence of their biology, including reproductive behavior, developmental stages and food,” he said. “There is no extant group that these fossils fit into, and we have no knowledge of any of their descendants living today. This discovery shows that unique lineages were surviving in the mid-Tertiary.

Perhaps other specialists will debate the taxonomy of this new critter he named “Sialomorpha dominicana” (“fat hog shape from Dominican Republic”), but it sure looks like a tardigrade. The news doesn’t say if it uses Dsup and is an extremophile. Poinar holds out the possibility that scientists may discover living examples of it. For now, there’s more to learn. Outwardly, “they share characteristics with both tardigrades” and mites, he says. It doesn’t look like a transitional form. It looks like a functioning member of its ecological niche. Poinar and Nelson’s paper is published in Invertebrate Biology.

Another Survivor

Some soft, squishy extremophiles were announced in Current Biology: a nematode that can survive 500 times the lethal dose of arsenic for humans! It and several other species of roundworms were discovered doing just fine in Mono Lake in California, known for its high salinity and soda that forms eerie towers of tufa rock along its shorelines.

Though Mono Lake has previously been described to contain only two animal species (brine shrimp and alkali flies) in its water and sediments, we report the discovery of eight nematode species from the lake, including microbe grazers, parasites, and predators. Thus, nematodes are the dominant animals of Mono Lake in species richness. Phylogenetic analysis suggests that the nematodes originated from multiple colonization events, which is striking, given the young history of extreme conditions at Mono Lake. One species, Auanema sp., is new, culturable, and survives 500 times the human lethal dose of arsenic.

The lab roundworm C. elegans lacks this kind of arsenic resistance. To keep Darwinists happy, the abstract of the paper calls the amazing trait a “preadaptation”:

This preadaptation may be partly explained by a variant in the gene dbt-1 shared with some Caenorhabditis elegans natural populations and known to confer arsenic resistance. Our findings expand Mono Lake’s ecosystem from two known animal species to ten, and they provide a new system for studying arsenic resistance. The dominance of nematodes in Mono Lake and other extreme environments and our findings of preadaptation to arsenic raise the intriguing possibility that nematodes are widely pre-adapted to be extremophiles. 

Another word for preadaptation is foresight. In evolutionary theory, preadaptation makes no sense, because Darwinian evolution, which only reacts to the immediate environment, has no foresight. 

On the other hand, as Marcos Eberlin argued convincingly in his book Foresight and in several podcasts on ID the Future, foresight is a marker for a designing intelligence.

Photo credit: Schokraie E, Warnken U, Hotz-Wagenblatt A, Grohme MA, Hengherr S, et al. (2012) [CC BY 2.5], via Wikimedia Commons.