10,000 year-old DNA proves when fish colonized lakes

DNA in lake sediment forms a natural archive displaying when various fish species colonized lakes after the glacial period. This according to researchers at the Department of Ecology and Environmental Science at Umeå University in a study published in the journal Methods in Ecology and Evolution. Their analyses of the prevalence of whitefish DNA in sediment reveal that the whitefish came to Lake Stora Lögdasjön in Västerbotten already 10,000 years ago, whereas Lake Hotagen in Jämtland had its whitefish only 2,200 years ago.

Lake Whitefish [Credit: Northwest Territories Tourism]

"It's fantastic news that DNA can be stored for so long in lake sediment. Normally, free DNA molecules break down within days, but certain DNA fragments are preserved because they bind to clay particles," says Professor Göran Englund, one of the researchers behind the study.

The DNA molecules in lake sediment are few and hard bound to particles. This resulted in challenging analyses and required development of new methods, both for extracting sufficiently clean DNA and for the statistical analysis of data. For this work, doctoral student Fredrik Olajos and researcher Folmer Bokma's efforts were of particular importance.

"Being able to map the prevalence of DNA in lake sediments is now opening up a new window into history, which lets us see how nature has developed over a long period of time," says Göran Englund. We have already started a project aiming to study how lake ecosystems are affected by historical climate changes. That can provide important clues to a better understanding of how the current global warming will affect ecosystems."

Researchers chose Stora Lögdasjön and Hotagen for the study since they expected the whitefish to have colonized these lakes at different points in time. Stora Lögdasjön was connected to the Baltic Sea when the inland ice melted around 10,000 years ago. The connection was cut off 9,200 years ago when the land uplift created a waterfall, Storforsen, which the whitefish was unable to travel up.

"Our hypothesis was that the whitefish colonized Stora Lögdasjön immediately after the ice-melt, which turned out accurate. Close to Hotagen, on the other side, there was a waterfall that prevented the whitefish from colonizing the lake after the ice melted," says Göran Englund.

Historic, written sources, however, show that whitefish has been found in Hotagen at least since the 18th century. Furthermore, the researchers were able to see that the speciation process that occur in many lakes -- namely that whitefish populations diverge into large-bodied and small-bodied species, had not developed as far in Hotagen.

"Based on this information, we assumed that the whitefish had colonized the lake long after ice-melt, but before the 18th century. It happening already 2,200 years ago was, however, a slight surprise," says Göran Englund.

"Naturally, we can't know for certain how the whitefish spread to Hotagen. Fish-eating animals like the otter, bear, osprey and dipper may have been involved, but the most likely theory is that hunters and fishermen who resided in the area 2,000 years ago played a part. We can see increasing evidence that fish species were introduced to new lakes by the humans that first colonized Scandinavia," concludes Göran Englund.

Source: Umeå Universitet [September 20, 2017]

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Celebrity fossil reveals all for science

With the help of an artist, a geology professor at Lund University in Sweden has figuratively speaking breathed life into one of science's most well-known fossil species; Agnostus pisiformis. The trilobite-like arthropod lived in huge numbers in Scandinavia a half-billion years ago. Today, this extinct species provides important clues for science in several ways.

Agnostus pisiformis [Credit: Esben Horn]

Despite its small size, Agnostus pisiformis is a remarkable and useful fossil. The extinct animal was just one centimetre in size when adult, but has been found exceptionally well-preserved and in large numbers. And it is not only the outer hard shells -- even the animal's soft tissue has been found so well preserved that it is possible to create extremely detailed sculptures that show what the tiny creature looked like.

"The sculptures have been greatly scaled up and show the animal's complete anatomy down to the smallest detail, including all the extremities and antennae," says Mats E. Eriksson, geology professor at Lund University.

Eriksson's research focuses mainly on microscopic fossils and attempts, among other things, to reconstruct ecosystems that are several hundred million years old.

The sculptures were created in connection with a research article he wrote on Agnostus pisiformis. He was assisted by the Danish artist and designer, Esben Horn, whose company, 10 Tons, specialises in producing lifelike sculptures of both extant and extinct organisms for museums and institutions around the world.

Agnostus pisiformis [Credit: Per Ahlberg]

The ancient Agnostus pisiformis is mainly known from Scandinavia, but it has been recorded also elsewhere, for example in England and Russia. Due to the fact that the species only lived for a limited period of time just over 500 million years ago, it is possible to use the fossilto date various rocks, which explains why Agnostus pisiformis is a celebrity within science.

However, the species is not only useful for researchers as a time reference, as it also gives them valuable insights into ancient life on Earth. This fossil is so well-preserved and occursin such large numbers that it is possible to understand its complete development, from juvenile to adult.

"The incredible degree of preservational detail means that we can grasp the entire anatomy of the animal, which in turn reveals a lot about its ecology and mode of life," says Mats E. Eriksson.

He now hopes that the sculptures of Agnostus pisiformis will become part of a travelling exhibition on the long lost faunas that existed in the oceans more than 500 million years ago. He wants to spread the knowledge about early lifeduring what he regards as a very exciting time in Earth history. He also wants to highlight that palaeontology, that is, the study of fossils, is not just about dinosaurs.

"There were actually ecosystems seething with fantastic and bizarre life forms several hundred million years before the dinosaurs even appeared," concludes Mats E. Eriksson.

The findings are published in Earth-Science Reviews.

Source: Lund University [September 15, 2017]

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A woman warrior from the Viking army in Birka

War was not an activity exclusive to males in the Viking world. A new study conducted by researchers at Stockholm and Uppsala Universities shows that women could be found in the higher ranks at the battlefield.

Illustration by Evald Hansen based on the original plan of the grave by excavator Hjalmar Stolpe, 
published in 1889 [Credit: Uppsala University]

Charlotte Hedenstierna-Jonson, who led the study, explains: "What we have studied was not a Valkyrie from the sagas but a real life military leader, that happens to be a woman".

The study was conducted on one of the most iconic graves from the Viking Age. It holds the remains of a warrior surrounded by weapons, including a sword, armour-piercing arrows, and two horses. There were also a full set of gaming pieces and a gaming board. "The gaming set indicates that she was an officer", says Charlotte, "someone who worked with tactics and strategy and could lead troops in battle". The warrior was buried in the Viking town of Birka during the mid-10th century. Isotope analyses confirm an itinerant life style, well in tune with the martial society that dominated 8th to 10th century northern Europe.

Anna Kjellstrom, who also participated in the study, has taken an interest in the burial previously. "The morphology of some skeletal traits strongly suggests that she was a woman, but this has been the type specimen for a Viking warrior for over a century why we needed to confirm the sex in any way we could."

The drawing is a reconstruction of how the grave with the woman originally may have looked. 
The illustration is made by Þórhallur Þráinsson [Credit: © Neil Price]

And this is why the archaeologists turned to genetics, to retrieve a molecular sex identification based on X and Y chromosomes. Such analyses can be quite useful according to Maja Krezwinska: "Using ancient DNA for sex identification is useful when working with children for example, but can also help to resolve controversial cases such as this one". Maja was thus able to confirm the morphological sex identification with the presence of X chromosomes but the lack of a Y chromosome.

Jan Stora, who holds the senior position on this study, reflects over the history of the material: "This burial was excavated in the 1880ies and has served as a model of a professional Viking warrior ever since. Especially, the grave-goods cemented an interpretation for over a century". It was just assumed she was a man through all these years. "The utilization of new techniques, methods, but also renewed critical perspectives, again, shows the research potential and scientific value of our museum collections".

The findings are published in American Journal of Physical Anthropology.

Source: Stockholm University [September 08, 2017]

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17th century royal flagship found in central Stockholm

Swedish archaeologists believe they have identified a shipwreck discovered in the capital as the more than 400-year-old warship 'Scepter', built in 1615 as one of the flagships in King Gustav II Adolf's fleet.

Harbour side view of the shipwreck [Credit: Jim Hansson, Stockholm Maritime Museum]

It was found in the summer during the renovation of the quayside on the Skeppsholmen islet which Stockholm Maritime Museum experts had been called out to oversee, marine archaeologist Jim Hansson told The Local.

"We were really surprised, because we have some old maps that show some wrecks from the early 1800s, and it seems like the older wrecks don't show up on the map. There were no indications of this wreck on the maps," he said, adding the remains uncovered include a section of the ship two metres up from the keel and parts of the transom.

"It was really well preserved. It is only to the first deck level, but you can still see the cut marks from the axes on the timber, for example. It's been really nice to excavate the parts."

"We took some chronological samples in the summer and we received the results which showed that wood is oak from Sweden, and it was cut in the winter between 1612 and 1613, which is a really good, precise measure. We then looked at the lists of the warships made at that time, and we found there were four big ships that were built then," he said, adding that the process of elimination suggests it is Scepter.

The remains of the ship [Credit: Johan Runer]

Scepter was built by Dutch shipbuilder Isbrand Johansson, weighing 800 tonnes and carrying 36 guns. She had an eventful life, including a journey in 1621 when she was part of a 148-ship fleet attempting to conquer Riga, with the King on board, but only made it to Pärnu, Estonia, after getting caught up in a storm.

In 1639 she was retired and was deliberately sunk at Skeppsholmen to form part of the foundation of a new shipyard being constructed at the islet in central Stockholm at the time – 17th-century recycling methods.

Historic vessels are a fascinating, but not unusual, discovery in the Swedish capital's shipwreck graveyard.

"It is really strange, almost like a mystery that a lot of these warships have just been forgotten, and here they are. When they don't have this dramatic story about how they sank, they are just forgotten. There are probably many more around the waters here, but they have just been forgotten. Which is very unusual for other countries, I think," said Hansson.

Stefan Płużański's painting of the Battle of Oliwa in 1627, in which Scepter may have participated
[Credit: WikiCommons]

"It's a really important find because the ship is from the generation before Vasa, so we can see the technical building methods that were used, and it can help us understand what went wrong with the Vasa as well," said Hansson, referring to Sweden's most famous warship, which sank on her maiden voyage in 1628. It was later salvaged, found to be largely intact and has since become one of Sweden's most popular tourist attractions.

But he emphasized Scepter will not be turned into another attraction in the style of the Vasa Museum.

"Definitely not. It is so expensive to preserve the Vasa, so we would need to find a really spectacular ship down here if we're going to build something like that. We've done some 3D photographs of the wreck, and documented it properly. And with the history, we are able to show so much about this ship already," he said.

The wreck has for now been left in approximately the same place as where it was found, and archaeologists will be on site as the renovation work continues, to be able to salvage any other marine treasures unearthed.

Authors: Emma Löfgren and Eugenia Tanaka | Source: The Local [September 07, 2017]

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