Scientists have discovered a rare mineral within a chiton tooth

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Scientists have discovered a rare mineral within a chiton tooth, a rare iron mineral called Santabarbarite that has never before been seen in a living organism, according to a paper to be published in the Proceedings of the National Academy of Sciences. Chitons are flattened, bilaterally symmetrical marine mollusks of the class Polyplacophora.

A chiton tooth

These creatures live all over the world, from cold waters to the tropics. Your teeth are one of the hardest materials known in nature. They are attached to a soft, flexible, tongue-like radula. Which burrows into rocks to collect algae and other food.

Lead author Dr. We have been fascinated by chitons for a long time, said Dirk Joster. The mechanical structures are only as good as their weakest link, so it is interesting to learn how chitons solve the engineering problem of how to connect your ultra-hard teeth to the soft underlying structure.

This remains a major challenge in modern construction, so we look to organisms like chiton to understand how it is done in nature, which has taken a few hundred million years to evolve. SEM image of the anterior end of the radula with mature Cryptochiton stelleri teeth.

In the study, Dr. Joster and his colleagues examined the teeth of Cryptochiton stelleri, a giant reddish-brown chiton sometimes affectionately referred to as “hobo meat.” They found a mineral called santabarbarite in a long.

Ultra-hard teeth

Hollow structure that connects the head of the tooth to the flexible membrane of the radula, which runs along the upper needle of the chiton. The pencil is like the root of a human tooth, connecting the cusp of our tooth to our jaw, said Dr. Joster.

It is a hard substance made up of extremely small nanoparticles in a fibrous matrix made up of biomacromolecules similar to the bones in our body. The researchers also tried to recreate this material in an ink designed for 3D printing. They developed a reactive ink that consists of iron and phosphate ions mixed in a biopolymer derived from chitin.

As the nanoparticle builds up in the biopolymer, it becomes stronger and more viscous. This mixture can easily be used for printing, said Dr. Joster. Post air drying results in a hard and rigid final material. We can continue to learn and develop from a material inspired by Chiton’s stylus, which combines ultra-hard teeth with a soft radula, he said.

National Academy of Sciences

Rare rock minerals found in mollusk teeth. A rare type of iron ore has been discovered for the first time in a living organism. Researchers at Northwestern University have discovered for the first time a rare mineral hidden within the teeth of a chiton, a large mollusk found along rocky shores. Before this strange wonder, iron ore, called santabarbarite, had only been documented in rocks.

The new discovery helps to understand how full chiton teeth, not just ultra-hard and durable caudal, are designed to tolerate chewing on rocks for food. Based on the minerals found in chiton teeth, the researchers developed a bio-inspired ink for 3D printing of ultra-hard, hard and durable materials.

“This mineral has only been observed in very small amounts in geological samples and has never before been observed in a biological context,” said Dirk Joster of Northwestern, lead author of the study. It has a high water content, which makes it stronger with a lower density.

We believe it can harden teeth without adding a lot of weight. The study will be published in the week of May 31 in the Proceedings of the National Academy of Sciences. Joster is an associate professor of materials science and engineering at Northwestern’s McCormick School of Engineering.

Linus Stegbauer, a former postdoctoral fellow in Joster’s lab, is the first author of the paper. While researching at Northwestern, Stegbauer is now a Principal Investigator at the Institute for Interfacial Process Engineering and Plasma Technology at the University of Stuttgart in Germany.

One of the hardest materials known in nature, chiton teeth are attached to a soft, flexible, tongue-like radula that scrapes through rocks to collect algae and other food. After studying chiton’s teeth for a long time, Joster and his team recently turned to Cryptochiton stelleri, a giant reddish-brown chiton sometimes affectionately referred to as “hobo meat.”

To examine the Cryptochiton stelleri tooth, Joster’s team collaborated with Erkan Alp, a senior scientist at Argonne National Laboratory’s Advanced Photon Source, to perform the facility’s Mössbauer synchrotron spectroscopy, as well as Paul Smits on the Northwestern Atomic University. Nanoscale Characterization and Experimentation Center (NUANCE).

They found that santabarbarite spans the entire upper style of the chiton, a long, hollow structure that connects the head of the tooth with a flexible radula membrane. “The pencil is like the root of a human tooth, connecting the cusp of our tooth to our jaw,” Joster said.

It is a resistant substance made up of extremely small nanoparticles in a fibrous matrix made up of biomacromolecules, similar to the bones in our body. Joster’s group took on the challenge of recreating this material in an ink designed for 3D printing.

Soft underlying structure

Steigbauer developed a reactive ink in which iron and phosphate ions were added to a biopolymer derived from chitin. In Mark Hersam’s lab, along with Northwestern graduate student Shay Wallace, Stegbauer found that ink printed well when mixed just before printing.

As the nanoparticles form into a biopolymer, it becomes stronger and more viscous. This mixture can easily be used for printing. Post-air drying results in a hard and rigid final material, Joster said. Joster believes that we can continue to learn and develop from a material inspired by the Chiton stylus, which combines ultra-hard teeth with a smooth razor.

Rare mineral within a chiton tooth
Rare mineral within a chiton tooth

“We have been fascinated by chitons for a long time,” he said. Mechanical structures are only as good as their weakest link, so it is interesting to learn how chitons solve the engineering problem of connecting your ultra-hard teeth to the soft underlying structure.

This remains a major challenge in modern construction, for what we look for organisms like chitons to understand how this is done in nature, which has taken a few hundred million years to evolve.

National Science Foundation (award number DMR-1508399 and DMR-1905982), National Institutes of Health (award number NIH-DE026952), Air Force Research Laboratory (award number FA8650-15-2-5518) and Deutsche Forschungsgemeinschaft (award number STE2689) / 1-1).

Eurasian horses
Eurasian horses

Eurasian horses a million years earlier than North American horses, DNA studies show. In new research, an international team of scientists sequenced and analyzed the mitochondrial and nuclear genomes of living and extinct horse horses (Equus spp.) To explore the possible effects of the Bering Land Bridge on genetic diversity and connectivity between a unique population. broad group.

Eurasian horses a million years ago

They found that the Eurasian horse population initially separated from North America, their ancestral continent, about 1 million years ago; After this division, he identified two long-distance bi-directional spans of the Bering Land Bridge 875,000–625,000 and 200,000–50,000 years ago.

Many times during the Pleistocene, ancient horses crossed the Bering Land Bridge in both directions between North America and Asia. Many times during the Pleistocene, ancient horses crossed the Bering Land Bridge in both directions between North America and Asia.

The horses that lived in North America

Image credit: Julius Cissotoni. Paleontologists have long known that horses evolved and diversified in North America. One lineage, the cabaline horse (which includes domestic horses), spread to Eurasia over the Bering land bridge about 1 million years ago, and the Eurasian population began to deviate genetically from the horses that lived in North America.

The new study suggests that after the split, there were at least two periods in which the horses moved from continent to continent and interbred, such that the North American horse genome acquired Eurasian DNA segments and vice versa. “This is the first comprehensive look at the genetics of ancient horse populations on both continents,” said Dr. Alisa Varshina, a postdoctoral researcher at the University of California, Santa Cruz.

“With data from both mitochondrial and nuclear genomes, we were able to see that horses were not only spreading between continents, but were also swapping and swapping genes.” Dr. Varshina and her colleagues sequenced 78 new mitochondrial genomes from ancient horses found in Eurasia and North America.

Eurasian horses in North America

Combining those with 112 previously published mitochondrial genomes, she reconstructed a phylogenetic tree, a branch diagram showing how all the samples are related. With a location and approximate date for each genome, they were able to trace the movements of different ancient horse lineages.

We found a lineage of Eurasian horses in North America and vice versa, suggesting population movements between continents, Dr. Varshina said. With dated mitochondrial genomes we can see when the location changes occurred. The analysis showed a span of two periods between continents, both coinciding with the period in which the Bering Land Bridge would have been open.

In the Middle Pleistocene, shortly after the divergence of the two dynasties, the movement was mainly from east to west. The second period of the late Pleistocene saw an impulse in both directions, but mainly from west to east. The researchers also sequenced two new nuclear genomes from well-preserved horse fossils recovered from the Yukon Territory, Canada.

These were combined with 7 previously published nuclear genomes, allowing the team to measure the amount of gene flow between the Eurasian and North American populations. “The general opinion in the past was that horses differentiated into different species as early as they were in Asia, but these results suggest that there was continuity between populations,” said Dr. Ross McPhee said.

Journal Molecular Ecology

“They were able to interbreed independently, and we see results in fossil genomes on both sides of the split.” The new findings help redefine the question of why horses disappeared from North America, said Dr. Grant Zazula, a paleontologist for the Yukon government. “It was a regional population loss rather than an extinction.

We still don’t know why, but it tells us that conditions in North America at the end of the last ice age were dramatically different. If horses didn’t cross Asia, they would have been. lost everyone on the world stage. ” The results were published in the journal Molecular Ecology.

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