Tag Archives: snail

The California sea hare, Aplysia californica. Credit: Wikimedia Commons.

Scientists transfer memories between snails with RNA implants


The California sea hare, Aplysia californica. Credit: Wikimedia Commons.

The California sea hare, Aplysia californica. Credit: Wikimedia Commons.

An exciting new research study suggests the possibility that some memories can be transferred between organisms. Scientists extracted ribonucleic acid (RNA) from a trained sea snail and implanted it into an untrained snail, whose behavior then matched that of the donor animal.

Where is my mind?

When the brain deems an experience meaningful enough, it will transfer that information from short-term storage — the temporary file cabinet which holds information like where you put your car keys or the phone number of a person you just met — to your long-term memory, where information is stored so that it can be accessed at a later time. Scientists think that this record is made in the brain by strengthening the connections between groups of neurons that participate in encoding the experience a pattern of connections which is referred to as an engram.

In 2012, MIT researchers identified the particular brain cells in the hippocampus that were active only when a mouse was learning about a new environment. They then proceeded to identify which genes were activated in those cells and added the gene for channelrhodopsin-2 (ChR2), a light-activated protein used in optogenetics, into a genetically engineered mouse. Using tiny optical fibers embedded in the animals’ skulls, the researchers could deliver pulses of light to hippocampal dentate gyrus neurons, thereby manipulating their activity. 

The mice were introduced to a new environment and were then left to acclimate themselves with a few minutes of exploration. A mild foot shock was then suddenly introduced, causing the mice to fear that environment. The activated brain cells were tagged with ChR2. Later, the mice were introduced in a totally different environment, with an obviously different maze and smell, and were again left there to explore. A pulse of light was fired onto the neurons involved in the first experience, causing the fear memory to switch on and the mice to quickly enter a defensive, immobile crouch. The rodents had, essentially, been fear conditioned.

“Our results show that memories really do reside in very specific brain cells,” co-author Xu Liu stated at the time, “and simply by reactivating these cells by physical means, such as light, an entire memory can be recalled.”

This landmark research study showed that long-term memories are stored in modified connections between brain cells, which can be recalled on command. However, recent evidence also points to an alternative explanation: memories might be stored in changes in gene expression induced by non-coding RNA (ncRNA) — an RNA molecule that is not translated into a protein.

Credit: Bédécarrats et al., eNeuro (2018).

Credit: Bédécarrats et al., eNeuro (2018).

David Glanzman and colleagues at the University of California, Los Angeles, trained a California sea hare (Aplysia californica) to form a conditioned response by stimulating their tail, triggering an involuntary defensive reflex. The team then proceeded to extract RNA from these trained snails and injected it into untrained animals. The latter group inherited a similar sensitized response.

Researchers also showed that RNA extracted from trained snails increased the excitability of cultured sensory neurons, which were obtained from untrained animals and which controlled the involuntary reflex.

The findings provide evidence that RNA may be involved in memory modification, which suggests that memory storage is far more complex than meets the eye.

Reference: RNA from Trained Aplysia Can Induce an Epigenetic Engram for Long-Term Sensitization in Untrained Aplysia, eNeuro.


Researchers develop very powerful but reversible glue — kind of like snail slime

An international team of snail-envious engineers has found a way to make powerful but reversive adhesives.


Image via Pixabay.

Nobody wants weak glue. It ruins your day. But another side of this sticky situation is reversibility. A strong glue can quickly become a liability when we stick something in the wrong position, for example. With a weak glue, you can un-stick something and try again — but risk it falling apart later when you need it to hold most. With a strong glue, you just have to deal with the mistake or start over from scratch — no adjustments allowed.

Except if you’re a snail. Snails, you see, have epiphragms — that slimy wet layer of mucus lathered all over their body. The epiphragm can harden to protect a snail’s body or to allow it to anchor in place for long periods of time. However, it can quickly be deactivated when the animal needs or wants too. The present study demonstrates a man-made alternative that functions much in the same way as a snail’s epiphragm.

Slime time

“Geckos can put one hand down and then release it, so the gecko’s adhesion is reversible, but it’s very low adhesion,” says Shu Yang, a Professor in the Department of Materials Science and Engineering and in the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania, who led the study.

“A gecko is 50 grams, and a human is at least 50 kilograms. If you want to hold a human on a wall, it’s not possible using the same adhesive. You could use a vacuum, but you have to carry a cumbersome vacuum pump. We’ve been working on this for a long time, and so have other people. And no one could have a better solution to achieve superglue-like adhesion but also be reversible.”

Yang and her team have a background in adapting nature’s creations to human technology and know-how. Among others, they have worked on nanoscale structures inspired by the structure of giant clams, butterflies, and pollen. Yang herself is also the director of AESOP, the Center for Analyzing Evolved Structures as Optimized Products, which looks at biology to solve design and architecture problems.

The geckos‘ adhesive toes aren’t strong enough to adapt to human use, she explains, although her team focused a lot of effort on making it work. However, the team had a breakthrough when Gaoxiang Wu, a Penn Engineering graduate student and co-author of the current paper, worked with a hydrogel made of a polymer called polyhydroxyethylmethacrylate (PHEMA) and noticed its unusual adhesive properties. PHEMA is rubbery when wet but becomes rigid as it dries — just like an epiphragm.

When PHEMA is wet, it can squish thoroughly into a surface texture, be that visible or microscopic. This part of the process makes it ‘sticky’. But what makes it a good adhesive is that when PHEMA begins to dry, it becomes very rigid — about as rigid as a plastic bottle cap, the team reports — but doesn’t shrink at all. This last step is the real meat and potatoes of the whole ‘adhesive’ thing. As the material hardens inside the cavities, it becomes securely tied to it.

“[PHEMA] is like those childhood toys that you throw on the wall and they stick. That’s because they’re very soft. Imagine a plastic sheet on a wall; it comes off easily. But squishy things will conform to the cavities,” says Yang.

“When materials dry, they usually shrink. If it shrinks from the surface, it no longer wants to conform to the microcavities and it’ll pop out. Our PHEMA adhesive doesn’t pop out. It stays conformal. It remembers the shape even when it’s dry and rigid.”

PHEMA works much like a snail’s epiphragm. This biological material, initially wet as it covers the snail’s body, sticks to any surface the animal moves over and eventually hardens. Snails often use their epiphragm to anchor them in place when they retreat into their shell. The material hardens into a solid ‘barricade’ around the shell’s opening, keeping it in place and insulating the snail from the dry, warm air during the day.


Which is why you see these hanging around.
Image credits Ulrike Leone.

At night, when temperatures drop and humidity rises, the epiphragm softens and the snail goes along its merry way.

The team tested both wet flexibility and dry adhesion for the PHEMA hydrogel in the lab, also evaluating its ability to hold weight and how long it needs to rehydrate and reverse its adhesive properties. The material was 89 times stronger than gecko adhesion but was easily broken after being rehydrated, the team reports. To showcase just what the material can pull off, the study’s co-first author Jason Christopher Jolly volunteered to suspend himself from a harness held only by a postage-stamp-sized patch of the PHEMA adhesive.

The glue held. The team says that although PHEMA may not be the strongest adhesive in existence, it is currently the strongest known candidate available for reversible adhesion.

“When it’s conformal and rigid, it’s like super glue. You can’t pull it off. But, magically, you can re-wet it, and it slips off effortlessly,” says Yang. “Additionally, PHEMA doesn’t lose its strong adhesion when scaled up. Usually, there’s a negative correlation between adhesion strength and size. Since PHEMA is not dependent on a fragile structure, it doesn’t have that problem.”

On the one hand, PHEMA could a huge development for scientific, industrial, and household applications. On the other hand, it’s also quite limited, since its activation is mediated by water. For example, a car glued together with PHEMA would, in other words, fall apart in the rain. So Yang acknowledges that it’s just a starting point.

“Car assembly uses adhesives, and, you can imagine, if there are any mistakes putting parts together, the adhesive is set and the parts are ruined,” she says.  “A car is pretty big. Usually they don’t glue things together until the last step, and you need a room-sized oven to host the car and cure the adhesives. An adhesive that’s strong and reversible like PHEMA could completely change the process of car assembly and save money because mistakes wouldn’t be so costly.”

“[However], with a lot of things you don’t want to use water. Water takes time to diffuse. In the future, we want to find the right material that can switch the property like that.”

The researchers hope to eventually find or engineer adhesives that could respond to cues like pH, specific chemicals, light, heat, or electricity, to broaden the potential applications of reversible adhesion.

The paper “Intrinsically reversible superglues via shape adaptation inspired by snail epiphragm” has been published in the journals Proceedings of the National Academy of Sciences.

Why snails coil in one direction — and how to change it

Many things in nature are symmetrical — think of your own body, for instance. Two arms, two legs, two eyes, and so on. Many creatures have some sort of natural symmetry, but nature and symmetry don’t always go together. You have a heart, and that’s (usually) on your left side, the liver is on your right, and for most people, one side of the body is handier than the other. Snails feature an even more impressive asymmetry: they coil to one side, and it’s almost always the right side. In a new study, Japanese researchers show why snails coil to the right, and how they can be edited to prefer the other side.

A shell of Lymnaea stagnalis, the snail used in the study. Image credits: Aung / Wikipedia.

If an object or a creature is distinguishable from its mirror image, its asymmetry is called chirality. All of the known life-forms show specific chiral properties, and animals such as gastropods (snails and slugs) exhibit remarkable chiral properties. They twist and produce coiled shells, but the direction of the coil isn’t random: in the vast majority of cases, gastropods twist to the right.

Researchers have previously suspected a gene Lsdia1 to be responsible for this, but until now, there was no practical confirmation. So Masanori Abe and Reiko Kuroda (working at Tokyo University of Science, but recently relocated to Chubu University, Japan) set out to explore how mutations of this gene might affect chirality.

They used CRISPR gene editing technology to tweak the gene — the first time this technology was applied to mollusks. From the earliest stages of development, even when the snail embryo was a single cell, there were signs of changing chirality. When the mutant snails grew as adults, they produced exclusively left-coiling offspring, showcasing that Lsdia1 was indeed responsible for chirality.

“It is remarkable that these snails with reversed coiling are healthy and fertile, and that this coiling can be inherited generation after generation (we now have 5th-generation leftward-coiling snails). Further, these results may have an implication for snail evolution and speciation — given that left- and rightward-coiling snails probably wouldn’t interbreed,” says Kuroda.

It’s not exactly clear how and why the gene controls chirality, however. Researchers know that Lsdia1 encodes formin, a group of cells found in all eukaryotes which are involved in a number of functions, including regulating cellular structure. Researchers believe that further studies of this gene could help us understand the mechanisms for controlling left-right asymmetry in all species — including our own. For instance, some babies are born with their heart on the right, which is commonly associated with life-threatening heart defects of the heart and other related abnormalities. Lsdia1 could hold the key to detecting and preventing these deformations.

“Although diverse mechanisms have been proposed for different animals, we think a unified mechanism, involving formins and cellular chirality, is probable,” Kuroda concludes.

The study has been published in the journal Development.

Scientists find the smallest snail

As far as titles go, ‘smallest snail’ isn’t really the one you’d like, but that’e exactly what Acmella nana will have to settle for. The tiny mollusk measures only 0.033 inches (0.86 mm) on average.

A tiny snail from Borneo is the smallest ever found, smaller than a period on a printed page. Identifying the shells in the wild required a microscope, researchers say.
(Photo : Menno Schilthuizen, Naturalis Biodiversity Center

When the biologists set out to find small snails, they knew exactly where to go; the limestone hills of Borneo area ideal because the shells of snails are built from calcium carbonate, the main component of limestone. The collection process is actually pretty crude.

“When we go to a limestone hill, we just bring some strong plastic bags, and we collect a lot of soil and litter and dirt from underneath the limestone cliffs,” said co-researcher Menno Schilthuizen, a professor of evolution at Leiden University in the Netherlands.

They sieve the contents, throwing away the larger objects into a bucket of water.

“We stir it around a lot so that the sand and clay sinks to the bottom, but the shells— which contain a bubble of air — float,” Schilthuizen said.

They then scoop the floating shells and sort them by size, using a microscope; usually, there’s a lot of them.

“You can sometimes get thousands or tens of thousands of shells from a few liters of soil, including these very tiny ones,” he said.

Researchers hand’t observed the species in the wild, so they don’t know what they eat or their breeding habits. However, they likely do many of the things that other small snails do – foraging on thin films of bacteria and fungi that grow on wet limestone surfaces in caves.

Due to its favorable conditions, Borneo boasts a large mollusk diversity, with over 500 snail species, but they are all very vulnerable to external influences, especially human influences. For example, a species can be limited to one limestone massif, and this limestone is quarried intensely. Scientists have already documented at least one species destroyed because its entire habitat was mined.

In addition to Acmella nana, researchers discovered another 47 snail species.

The research is published in Zoo Keys.



Moving snails at least 20m away reverses homing instinct


Photo: scribol.com

For the casual nature enthusiasts, snails are a infinite source of joy whenever people come across them. People like to study them and revere how beautiful they are in their own microcosmos – for a while at least, until they get bored that is; it’s a slow paced microcosmos after all. For others, snails are nothing more than pests; slimy critters who wreck havoc in gardens. Instead of using chemicals or messy beer traps, like some gardeners employ, it’s better maybe to simply throw away the snails out of your backyard. A new research found that a safe distance for moving snails so they lose their homing instinct and can’t naturally return to the original spot you found them is about 20 meters. No snails were hurt during the course of this study.

The snail wars…

A famous experiment from 2010 proved that snails have a homing instinct over short distances, returning to their original spots. While this is true, according to researchers at Queen Mary, University of London and the University of Exeter this homing instinct can be overcome for many snail populations. If the pests are removed by at least 20 meters from their home patch, they will largely be unlikely to return.

[ALSO READ] Snail venom inspires powerful pain reliever without any addiction 

Does this mean we can expect hundreds of hurling snails tugged from one garden to another by bothered neighbors? Might be the case for a while if the right people read this article, but even if you manage to remove a large proportion of the blighters, they are likely to repopulate your herbaceous borders alarmingly quickly. This is because there are two distinct populations of snails: the kind who show little affinity to the garden itself (these comprise the bulk of snails) and the kind who stick to the local garden exclusively and regularly return to their home if removed. It’s the latter the can be thrown away never to come back.

[MORE] Getting across: how snail travel through birds’ bellies

The 20 meter margin was chosen after researchers marked snails with correction fluid and checked the plants to see whether they returned if lobbed away. Then statistical analysis of the empirical data showed that removing snails by distances of more than 20 metres is usually sufficient to nullify their homing instinct.

David Dunstan, professor at Queen Mary University of London and co-author of the research study published in the journal Physica Scripta, said: “We showed that the number of snails regularly or irregularly visiting a garden is many times greater than the number actually present at any one time in the garden. As such, gardeners shouldn’t be setting out to eliminate snails from their gardens. To achieve such a feat would require the gardener to rid the whole neighbourhood of snails, which would be a slow process. Gardeners should be setting out to minimise the damage done by snails, which our results showed could be quickly achieved by simply removing the snails over 20 metres away.”

A tornatellides boeningi. Image credit: rakuten.co.jp

Getting across: how snails travel through birds’ bellies

New York to Paris – 8 hours. Who in their right minds would’ve thought 100 years ago that you could span more than 3600 miles in this kind of time span? Aviation has changed the way we view time and distances forever, and consequently the world is a much smaller place now. Humans aren’t the only non-winged beings, however, to travel great distances by flight, as scientists have shown that snails are able travel long distances via birds’ bellies.

A tornatellides boeningi. Image credit: rakuten.co.jp

A tornatellides boeningi. Image credit: rakuten.co.jp

At first, the researchers from Japan, were curious whether or not snails could indeed do this after they found snail remains in bird feces. Seeds are widely known to get spread by fruit-eating birds, and with this in mind they believed some snails could survive digestion and come out alive.

To validate their point, they chose a certain snail species called Tornatellides boeningi and began running tests. As such, the researchers fed 119 adult snails to Japanese white-eyes and 55 snails to brown-eared bulbuls – 15% of the snails came out alive. Well, alive and covered in poop that is, but alive nevertheless.

The biggest factor, scientists noticed, that helped snails stay alive was their size – the smaller the size, the bigger the chance they had of surviving was. The researchers think that T. boeningi may be able to produce mucus that protects them from the birds’ digestive fluids, but this is a topic for future research. Actually, in a curiour turn of events, one of the snails gave birth to offsprings not long after exiting its aviary means of transportation. The researchers believe that passing through the gut of birds may be a cue for pregnant snails to give birth, as this would enhance the snails’ probability of colonizing new areas.

Are the snail naturally dispersing this way though or did scientists just prove that they can survive inside a bird’s tummy? Well, researchers reckoned that if the snails didn’t move around in this way than the genes of snail populations living in condensed areas should be very similar. This was not the cased, as researchers noticed a high level of variance in the gene flow. This means that the genes of isolated communities communicate with one another, despite the relatively large distances between them. Seeing how we all know how fast a snail can be, the aviary airline explanation seems to be vast enough.

An added bonus - presenting the Birdsnail!

An added bonus - presenting the Birdsnail!