̽��ֱ�� of Cambridge - Virginia Tech

‘Missing’ sea sponges discovered

sc604 — Wed, 05 Jun 2024 12:56:30 +0000

At first glance, the simple, spikey sea sponge is no creature of mystery.

No brain. No gut. No problem dating them back 700 million years. Yet convincing sponge fossils only go back about 540 million years, leaving a 160-million-year gap in the fossil record.

In a paper released in the journal Nature, an international team including researchers from the ̽��ֱ�� of Cambridge, have reported a 550-million-year-old sea sponge from the “lost years” and proposed that the earliest sea sponges had not yet developed mineral skeletons, offering new parameters to the search for the missing fossils.

̽��ֱ��mystery of the missing sea sponges centred on a paradox.

Molecular clock estimates, which involve measuring the number of genetic mutations that accumulate within the Tree of Life over time, indicate that sponges must have evolved about 700 million years ago. And yet, there had been no convincing sponge fossils found in rocks that old.

For years, this conundrum was the subject of debate among zoologists and palaeontologists.

This latest discovery fills in the evolutionary family tree of one of the earliest animals, connecting the dots all the way back to Darwin’s questions about when the first animals evolved and explaining their apparent absence in older rocks.

Shuhai Xiao from Virginia Tech, who led the research, first laid eyes on the fossil five years ago when a collaborator texted him a picture of a specimen excavated along the Yangtze River in China. “I had never seen anything like it before,” he said. “Almost immediately, I realised that it was something new.”

̽��ֱ��researchers began ruling out possibilities one by one: not a sea squirt, not a sea anemone, not a coral. They wondered, could it be an elusive ancient sea sponge?

In an earlier study published in 2019, Xiao and his team suggested that early sponges left no fossils because they had not evolved the ability to generate the hard needle-like structures, known as spicules, that characterise sea sponges today.

̽��ֱ��team traced sponge evolution through the fossil record. As they went further back in time, sponge spicules were increasingly more organic in composition, and less mineralised.

“If you extrapolate back, then perhaps the first ones were soft-bodied creatures with entirely organic skeletons and no minerals at all,” said Xiao. “If this was true, they wouldn’t survive fossilisation except under very special circumstances where rapid fossilisation outcompeted degradation.”

Later in 2019, Xiao’s group found a sponge fossil preserved in just such a circumstance: a thin bed of marine carbonate rocks known to preserve abundant soft-bodied animals, including some of the earliest mobile animals. Most often this type of fossil would be lost to the fossil record. ̽��ֱ��new finding offers a window into early animals before they developed hard parts.

̽��ֱ��surface of the new sponge fossil is studded with an intricate array of regular boxes, each divided into smaller, identical boxes.

“This specific pattern suggests our fossilised sea sponge is most closely related to a certain species of glass sponges,” said first author Dr Xiaopeng Wang, from Cambridge’s Department of Earth Sciences and the Nanjing Institute of Geology and Palaeontology.

Another unexpected aspect of the new sponge fossil is its size.

“When searching for fossils of early sponges I had expected them to be very small,” said co-author Alex Liu from Cambridge’s Department of Earth Sciences. “ ̽��ֱ��new fossil can reach over 40 centimetres long, and has a relatively complex conical body plan, challenging many of our expectations for the appearance of early sponges”.

While the fossil fills in some of the missing years, it also provides researchers with important guidance about what they should look for, which will hopefully extend understanding of early animal evolution further back in time.

“ ̽��ֱ��discovery indicates that perhaps the first sponges were spongey but not glassy,” said Xiao. “We now know that we need to broaden our view when looking for early sponges.”

Reference:
Xiaopeng Wang et al. ‘A late-Ediacaran crown-group sponge animal.’ Nature (2024). DOI: 10.1038/s41586-024-07520-y

Adapted from a Virginia Tech press release.

̽��ֱ��discovery, published in Nature, opens a new window on early animal evolution.

Xiaopeng Wang

Heliocolocellus fossil

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Silent flights: How owls could help make wind turbines and planes quieter

sc604 — Sun, 21 Jun 2015 23:03:07 +0000

An investigation into how owls fly and hunt in silence has enabled researchers to develop a prototype coating for wind turbine blades that could significantly reduce the amount of noise they make.

Early tests of the material, which mimics the intricate structure of an owl’s wing, have demonstrated that it could significantly reduce the amount of noise produced by wind turbines and other types of fan blades, such as those in computers or planes. Since wind turbines are heavily braked in order to minimise noise, the addition of this new surface would mean that they could be run at much higher speeds – producing more energy while making less noise. For an average-sized wind farm, this could mean several additional megawatts worth of electricity.

̽��ֱ��surface has been developed by researchers at the ̽��ֱ�� of Cambridge, in collaboration with researchers at three institutions in the USA. Their results will be presented today (22 June) at the American Institute of Aeronautics and Astronautics (AIAA) Aeroacoustics Conference in Dallas.

“Many owls – primarily large owls like barn owls or great grey owls – can hunt by stealth, swooping down and capturing their prey undetected,” said Professor Nigel Peake of Cambridge’s Department of Applied Mathematics and Theoretical Physics, who led the research. “While we’ve known this for centuries, what hasn’t been known is how or why owls are able to fly in silence.”

Peake and his collaborators at Virginia Tech, Lehigh and Florida Atlantic Universities used high resolution microscopy to examine owl feathers in fine detail. They observed that the flight feathers on an owl’s wing have a downy covering, which resembles a forest canopy when viewed from above. In addition to this fluffy canopy, owl wings also have a flexible comb of evenly-spaced bristles along their leading edge, and a porous and elastic fringe on the trailing edge.

“No other bird has this sort of intricate wing structure,” said Peake. “Much of the noise caused by a wing – whether it’s attached to a bird, a plane or a fan – originates at the trailing edge where the air passing over the wing surface is turbulent. ̽��ֱ��structure of an owl’s wing serves to reduce noise by smoothing the passage of air as it passes over the wing – scattering the sound so their prey can’t hear them coming.”

In order to replicate the structure, the researchers looked to design a covering that would ‘scatter’ the sound generated by a turbine blade in the same way. Early experiments included covering a blade with material similar to that used for wedding veils, which despite its open structure, reduced the roughness of the underlying surface, lowering surface noise by as much as 30dB.

While the ‘wedding veil’ worked remarkably well, it is not suitable to apply to a wind turbine or aeroplane. Using a similar design, the researchers then developed a prototype material made of 3D-printed plastic and tested it on a full-sized segment of a wind turbine blade. In wind tunnel tests, the treatment reduced the noise generated by a wind turbine blade by 10dB, without any appreciable impact on aerodynamics.

While the coating still needs to be optimised, and incorporating it onto an aeroplane would be far more complicated than a wind turbine, it could be used on a range of different types of wings and blades. ̽��ֱ��next step is to test the coating on a functioning wind turbine. According to the researchers, a significant reduction in the noise generated by a wind turbine could allow them to be spun faster without any additional noise, which for an average-sized wind farm, could mean several additional megawatts worth of electricity.

̽��ֱ��research was funded by the US National Science Foundation and the US Office of Naval Research.

Inset image: Close-up view of a flight feather of a Great Grey Owl. Credit: J. Jaworski.

Homepage image: Owl, by Mirko Zammarchi via Creative Commons

A newly-designed material, which mimics the wing structure of owls, could help make wind turbines, computer fans and even planes much quieter. Early wind tunnel tests of the coating have shown a substantial reduction in noise without any noticeable effect on aerodynamics.

No other bird has this sort of intricate wing structure

Nigel Peake

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Flying snowy owl

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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