Tag Archives: Shells

‘Penis worms’ invented the hermit lifestyle some 500 million years ago by moving into discarded shells

The “hermit” lifestyle best known from crabs today was first invented 500 million years ago by worms, new research reveals.

Illustration of a Cambrian penis worm inhabiting a hyolith shell. Image credits Zhang Xiguang.

Hermit crabs today are famous for seeking out and taking residence in discarded snail shells. This offers the animals protection against predators while allowing them to avoid the huge energy and nutrient costs associated with building such a shell from scratch. It’s quite an effective strategy for the crabs.

However, they’re not the ones to first think of it. Researchers at Durham University and Yunnan University report that penis worms (phylum Priapulida) were busy taking up residence in discarded shells during the Cambrian period some 500 million years ago. This is the oldest known evidence of the ‘hermit’ lifestyle that we’ve found so far, the team adds.

Renting a place

“Priapulan-like worms were very common in the Cambrian, sometimes forming shallow burrows but often moving along the surface of the sea bed,” said Dr. Martin R. Smith, an Associate Professor in Palaeontology at Durham University and a co-author of the paper, in an email for ZME Science. “Some had little defensive plates or built their own tubes for protection from predators; others even had little claw-like hooks on their underside to help them move about.”

“Today, priapulans are only found in hard-to-inhabit places, such as those with low oxygen, or miniaturized between sand grains — places where predators find it hard to make a living. We used to think that predators struggled a bit in the Cambrian too, but clearly — at least in the Guanshan [area, where these worm fossils vere recovered] — predators were enough of a threat to make priapulans reach for a more ‘modern’ style of defensive mechanism!”

Fossil deposits in the Guanshan, an urbanized area in southeastern Taiwan. The fossil deposits in this area are famous for often preserving soft tissue alongside harder material such as shells, which is quite rare for fossils. Four specimens of penis worms in the genus Eximipriapulus from this area were recovered inside the conical shells of hyoliths, another group of long-extinct animals.

“The worms are always sitting snugly within these same types of shells, in the same position and orientation. My first thought was ‘can I be sure that this isn’t a coincidence’, so we had to look hard at the fossils to be sure that the worms were in (rather than on or below) the shells, that the relationship was consistent, etc.,” explains Dr. Smith for ZME Science.

The findings cast new light on our understanding of the ecosystem relationships during the Cambrian. This was a geological period that was a hotbed of evolution, with many and exotic forms of life appearing all over the planet. The rapid evolutionary changes during this time have earned it the nickname of the “Cambrian explosion”. And some very peculiar lifeforms appeared during this time; in many ways, life on Earth during the Cambrian was quite alien-looking.

It was definitely a valuable time in history. The trial-and-error that happened during this time led to the emergence of what we’d call ‘the modern’ animal body.

But more to the point, the high rates of diversification during the Cambrian led to the emergence of predators in many environments where they were completely lacking before. This, in turn, led to an arms race between predator and prey that still continues to this day.

“The only explanation that made sense was that these shells were their homes – something that came as a real surprise,” Dr Smith adds in a press release. “Not long before these organisms existed, there was nothing alive more complex than seaweeds or jellyfish: so it’s mind-boggling that we start to see the complex and dangerous ecologies usually associated with much younger geological periods so soon after the first complex animals arrive on the scene.”

Hermit crabs today take permanent residence in the shells they find laying on the sea bottom, carrying them around on their backs. The team believes penis worms also carried hyolith shells around, that they “likely dragged the shells with them”, Dr. Smith told me.

“We believe that they dwelt in them permanently (except to up-size when they grew). It’d be lovely to see trace fossils showing the grooves made by dragging the shells, but as the fossils were transported to their resting place, we don’t have definitive evidence,” he told ZME Science.

Hermit crabs today eventually outgrow their shells. Groups of hermit crabs looking for an upgrade will often get together and line up from smallest to largest, then trade shells among themselves. It’s a pretty handy way to make sure that everybody has at least a shell, and that most crabs have a proper shell to live in (some, sadly, are left with shells that are a bit too tiny or defective in some way). I asked Dr. Smith whether there’s any sign that the worms engaged in similar social behavior to find shells to inhabit.

“No evidence, and there seems to have been no shortage of shells in this environment, so it probably didn’t happen in Guanshan – but we don’t have evidence to say either way,” he explaned for ZME Science. “I’d be surprised if they did, as this ‘feels’ like a sophisticated behaviour for this group, and for the Cambrian period  – but then I would have said that about hermiting at all before I saw these fossils!”

Despite their hermiting lifestyle, penis worms were not helpless beasts in their ecosystems. Dr. Smith tells me that shells from brachiopods (lamp shells), trilobites, and hyoliths have been found in the guts of penis worms related to the ones the team investigated here.

“Worth mentioning that ecologically, priapulans were both predators and prey; many fed on organic material within mud, but others scavenged and some may have been active predators themselves,” he told ZME Science.

The findings are valuable as they represent the earliest known case of an animal engaging in a hermit lifestyle. It gives us context to better understand the ecosystem dynamics of the Cambrian period, and of the emergence of wide-scale predation on Earth.

The paper “A ‘hermit’ shell-dwelling lifestyle in a Cambrian priapulan worm” has been published in the journal Current Biology.

Scientists develop memory chips from egg shells

Eggshells might become the data storage of the future. A Chinese team showed that the material can be used to create greener RAM storage for out computers.

Image credits Steve Buissinne / Pixabay.

You’ve heard of eggplants, but what about eggcomputers? Seeking to bring the term about, a team from the Guizhou Institute of Technology hatched a cunning plan: they went to the market, bought a few random eggs, and ground their shells for three hours to make a homogeneous, nano-sized powder. After it was dry, the team mixed this powder into a solution and poured it onto a substrate.

They thus ended up with the part of a memory chip through which electricity actually flows — the electrolyte. But eggshells are not an item you tend to see in chip factories, so how could it function as RAM? Well, the team tested the egg-paste to see if it changes its electrical resistance when a voltage flows through it. This property can be used to create memory chips of the ReRAM, or resistive random access memory, variety. There’s a lot of interest in ReRAMas it could be used to create faster, denser, and more energy efficient storage media than traditional RAM or flash memory.

And it worked. The team was able to encode 100 bits of binary information into the eggmemory before it failed. It doesn’t stack up to the billions of cycles regular materials can take, but as a proof of concept it’s incredible.

It’s ground eggshell. That can store binary data.

Still, we’re a long way off from seeing one of these devices on the market. But if they do show promise for future applications and, with enough developement, could provide a clean, sustainable, and very egg-y alternative to the electrolytes in use today.

The full paper “A larger nonvolatile bipolar resistive switching memory behaviour fabricated using eggshells” have been published in the journal Current Applied Physics.

Fossil Friday: the earliest known shells from 809 million years ago

The oldest evidence of biomineralization has been discovered 200 million years earlier than previously thought.

These structures might be the oldest known evidence of organisms building shells to defend themselves. They take many shapes, including this honeycomb pattern.
Image credits P. Cohen.

Talking at the Geological Society of America’s annual meeting on September 27, paleobiologist Phoebe Cohen described the oldest known fossilized eukaryotes. The “apatitic scale microfossils”, discovered in the Fifteenmile Group in Yukon, Canada, are layered out in armor-like sheets of mineral plates which formed about 809 million years ago — making them the oldest evidence we have of organisms using biomineralization for protection.

This new date of the shift towards biomineralization reflects changing ecosystems — there’s little point in building a shell if no one tries to eat you — coinciding with the end of a period known as the “boring billion” (the Mesoproterozoic era in science-speak). It also shows changing chemical conditions in the oceans at the time. Shelled creatures today trap a lot of carbon, forming an important part of the modern carbon cycle — as the critters die, their shells sink to the bottom of the ocean, removing this element from the atmosphere.

“We have been able to identify specific conditions that facilitated the evolution of the first eukaryote to biomineralize in Earth’s history,” Cohen, who studies ancient ecosystems at Williams College in Williamston, Mass, said.

“It paints a beautiful picture of the ecology and evolution and environmental conditions that led to this dramatic innovation.”

Previous evidence suggests eukaryote biomineralization appeared around 560 million years ago in primitive coral-like animals. But in those times, organisms built their shells very differently than how they organisms go about it today. The discovery of these fossils thus offers insight into how shell building first evolved, Cohen added.

The fossils were first retrieved in the late 1970s, and even then many paleontologists believed that they hinted at an earlier start for biomineralization. But the dating techniques of the day couldn’t pinpoint their age very accurately, and scientists couldn’t rule out the possibility that the minerals they were dating were there before the organisms died. Cohen and her team revisited the fossils — by dating shale rich in organic material a few meters below the fossil in the rocks, they determined their age at 809 million years old.

Using an electron microscope, they determined that each plate was weaved out of elongated mineral fibers. This structure is too orderly not to have been made by living organisms, Cohen said. They’re made of calcium phosphate, unlike modern shells which are built from calcium carbonate. Today, phosphate is scarce in the environment and it’s too valuable for microbes to waste it.

An electron microscope let researchers see that each plate is a weave of elongated mineral fibers. This intricate, orderly design had to have been purposefully built by life manipulating mineral formation, Cohen said. But 809 million years ago, oxygen levels in the water fluctuated wildly, an analysis of the surrounding rocks showed. This pulled phosphates from the sediment into the waters, so it was in plentiful supply.

Together with the emerging threat of predators, this abundance of phosphate drove eukaryotes to bunker up, Cohen said. Environmental changes eventually lead to these intrepid shell-builders going extinct.