Tag Archives: crab

Plastic pollution is killing off the hermit crabs

Over half a million hermit crabs on remote islands were killed by plastic washing off on the beach. The plastic pieces on beaches create physical barriers and traps that the crabs cannot escape.

Marine debris has become a common sight on many of the world’s beaches. Image credits: Susan White/USFWS.

Beaches all around the world are drowning in plastic — quite literally. That’s not a new realization. But as Jennifer Lavers and her research team were looking through the debris, they found something unsettling: crabs — lots and lots of crabs.

“When we were surveying debris on the islands, I was struck by how many open plastic containers contained hermit crabs, both dead and alive,” Dr. Lavers recalls.

It became clear that debris on beaches and in coastal vegetation creates a barrier for hermit crabs — which oftentimes they cannot escape. So Lavers and colleagues decided to do a survey across many islands with significant crab populations.

They analyzed a range of sites, looking at how many containers were on the beaches, whether or not they were open and in a position to be a trap, and how many actually contained crabs.

The findings are disconcerting.

“Our calculations show more than 500,000 hermit crabs died from being trapped in containers on the Cocos (Keeling) Islands and 60,000 on Henderson island.”

“These results are shocking but perhaps not surprising, because beaches and the vegetation that fringes them are frequented by a wide range of wildlife. It is inevitable that these creatures will interact with and be affected by plastic pollution, although ours is one of the first studies to provide quantitative data on such impacts.”

The plastic trap is insidious because it plays into the crabs’ biological signals. When a hermit crab dies, it emits a chemical signal to let others know that a potential shell has become available, explained Alex Bond, a curator of London’s Natural History Museum, which assisted in the study.

Thus, a crab that dies after trying to make a home out of plastic sets off an insidious chain reaction: the smell attracts another who dies, and so on, until a very strong signal is produced, drawing most of the crabs in the area. It’s not as much a domino effect as it is an avalanche, Bond said.

This damage is expected to cascade throughout the environment. Hermit crabs play a crucial role by aerating and fertilizing soil, researchers emphasize. They also disperse seeds and detritus, so the degradation of hermit crabs spills into the entire food chain.

Humans also rely on these ecosystems for fishing and tourism, so there is also direct economic damage. The study also only analyzed a part of the crabs’ habitats, so the global damage might be well higher.

A survey from earlier this year found a disturbing amount of plastic on Cocos Island, which is one of the main habitats of hermit crabs, including 977,000 shoes and 373,000 toothbrushes.

Journal Reference: https://doi.org/10.1016/j.jhazmat.2019.121703

Crabs can solve mazes and find their way out

Dr. Poe and one of the shore crabs used in the study. Credit: Swansea University

Spatial learning is an important cognitive ability in many animals. Often, scientists entice mice to find their way out of complex mazes in order to study their behavior and learn more about how the mammalian brain handles navigation. In fact, this kind of research won May-Britt Moser and Edvard I. Moser the 2014 Nobel Prize in Physiology for their discoveries of cells that constitute a positioning system in the brain.

But, not nearly enough attention has been granted to studying spatial learning in non-mammalian animals. Seeking to bridge the gap, Ed Pope and Ross Davies, both at Swansea University in the UK, investigated whether crustaceans could navigate a complex maze.

They tested 12 shore crabs over a four week period, which had to reach a tasty mussel at the end of the maze. To hit their goal, the crabs had to make five changes in direction and avoid three dead ends.

“Spatial learning is quite complicated, so figuring out how it works in crustaceans gives us a better understanding of how widespread this ability, and learning in general, is in the animal kingdom,” Pope said.

Schematic of the experimental maze that the shore crabs had to navigate. Credit: Swansea University.

After the initial training, the researchers noticed that the crabs showed improvements in the time it took them to find the food and took fewer wrong turns. When they were placed in the maze again two weeks later, this time without any food at the other end to act as a reward, the crabs still reached the other end in under eight minutes.

Clearly, the crabs remembered their way. For instance, new crabs that were totally unadjusted to their surroundings took far longer to reach the end of the maze and some couldn’t complete it at all at the end of the one-hour study period.

“This study is important because we know that insects, especially ants and bees, have some impressive mental abilities but we haven’t really looked for them in their aquatic counterparts. The fact that crabs show a similar ability to insects is, in some ways, not that surprising but it is great to be able to show it so clearly. This work opens the door to more sophisticated experiments looking at how changing ocean conditions might affect crabs’ ability to learn and adapt to find food in future,” Pope said.

Mary Gagen, a climate change expert at Swansea and co-author of the new study, says that the findings are important in the context of a shifting climate.

“We know so much is changing in our oceans due to human caused climate change. Gaining a baseline understanding of the lives of the animals that are going to actually be impacted by the changes in our future oceans is really important. That doesn’t just mean the big charismatic animals, it means things like crabs that are so important for the food chain.”

The findings appeared in the journal Biology Letters.

Chimps also love to eat crabs, new study shows

While chimps’ diet is mainly vegetarian, they will sometimes supplement it with other types of nutrients. Turns out, crabs are also on the menu.

“Our study is the first evidence showing that non-human apes regularly catch and eat aquatic fauna,” says Kathelijne Koops, one of the study authors.

Chimpanzee fishing for crabs. Image credits: Kathelijne Koops.

Chimps eat a lot of plants, including fruits, leaves, nuts and seeds. They’ll also occasionally eat meat or even honey, which they have advanced methods of accessing. However, they’re still largely vegetarian, with animal products accounting for around 6% of their nutrient intake. A new study, however, found a new entry on the chimps’ menu: crabs.

Koops and colleagues found that chimps in the rainforests of the Nimba Mountains in Guinea searched for streams in the forest. After finding a stream, they scratch its surface, churning the riverbed and looking for crabs to eat.

Chimps ate crabs all ear round, regardless of whether there were ripe fruits available as an alternative. Their preference for crab was also equal in the dry and rainy season, as even during the dry season, there’s still enough water to host some crabs. The one thing that was counterbalanced by crabs was ant consumption: the more insects they ate, the fewer crabs, and vice-versa, suggesting that crabs and ants have similar nutritional value for chimps.

This wasn’t the only surprise, however.

“Female chimpanzees and their offspring fished for crabs more often and for longer than adult males, which we had not expected,” says anthropologist Koops. A possible explanation for this is that the nutrients in the crabs (especially fatty acids) are better for maternal and infant health, but it’s unclear if this is the case. Mothers were also found to teach their children the crab fishing technique.

These findings don’t just shed new light about our closest living relatives, but they could also teach us a thing or two about our own evolution. Anthropological research has shown that for hominins, aquatic fauna has become a more and more important source of nutrition over time, with one theory stating that consuming aquatic fauna helped evolve bigger, more potent brains, as they contain high amounts of unsaturated fatty acids.

“The aquatic fauna our ancestors consumed likely provided essential long-chain polyunsaturated fatty acids, required for optimal brain growth and function,” said first author Dr Kathelijne Koops.

For now, however, this is still a theory. What is clear is that chimps sure love their crab.

Journal Reference: Koops et al. Crab-fishing by chimpanzees in the Nimba Mountains, Guinea. Journal of Human Evolution. Doi: 10.1016/j.jhevol.2019.05.002.

Callichimaera perplexa.

Fossil Friday: newly-discovered Callichimaera perplexa is an adorable, weird crab

A newly-discovered ancient species is forcing scientists to rethink what exactly counts as a crab.

Callichimaera perplexa.

Image credits Oksana Vernygora / University of Alberta.

An international team led by paleontologists from the Yale University announced the discovery of a treasure trove of hundreds of well-preserved crab specimens. The fossils include species of true shrimp, comma shrimp and, most excitingly, a new branch of the evolutionary tree of crabs. The specimens were recovered from Colombia and the United States and date back to the mid-Cretaceous (around 90 to 95 million years ago).

Googly-eyed by design

“Callichimaera perplexa is so unique and strange that it can be considered the platypus of the crab world,” said Javier Luque, who led the research efforts.

“It hints at how novel forms evolve and become so disparate through time. Usually we think of crabs as big animals with broad carapaces, strong claws, small eyes in long eyestalks, and a small tail tucked under the body. Well, Callichimaera defies all of these ‘crabby’ features and forces a re-think of our definition of what makes a crab a crab.”

Reconstruction.

Reconstruction of Callichimaera perplexa.
Image credits J. Luque et al., 2019, Science Advances.

The team writes that Callichimaera perplexa is one of the earliest species of paddle-legged, swimming anthropods we’ve ever discovered, second only to the group of sea scorpions (which lived more than 250 million years ago). It was named for the chimera, a mythological creature whose body included features from several animals. Its full name translates to “perplexing beautiful chimera.”

The specimen, which Luque describes as “unusual and cute”, is definitely perplexing. The ancient crab was quite tiny, about the size of a quarter. It also had a striking pair of large, compound eyes — but no eye sockets. Bent claws, leg-like mouthparts, and a long body ending in an exposed tail completed its visage.

These latter features are typical of pelagic crab larvae to this day, the team writes. This suggests an evolutionary link tying them to the ancient species. The team believes that these traits were retained and amplified in ‘miniaturized adults’ through changes in the timing and rate of development. This process, called “heterochrony,” is one of the mechanisms through which species evolve novel body parts.

“It is very exciting that today we keep finding completely new branches in the tree of life from a distant past, especially from regions like the tropics, which, despite being hotspots of diversity today, are places we know the least about in terms of their past diversity,” Luque said.

The paper “Exceptional preservation of mid-Cretaceous marine arthropods and the evolution of novel forms via heterochrony,” has been published in the journal Science Advances.

Microplastics.

Microplastics could break down whole ecosystems — they’re making prey unresponsive to predators

Our microplastics are a much more important factor in the health of the ocean than suspected. And they’re up to no good.

Microplastics.

Microplastics.
Image credits Oregon State University / Flickr.

Researchers at the French National Centre for Scientific Research report that microplastics can disrupt predator-prey relationships in the wild. In a new study, the group describes the impact of microplastic consumption on the common periwinkle (Littorina littorea).

Micropastics, macro effects

Periwinkles are a kind of sea snail. They’re not… particularly exciting. They sit on algae-encrusted rocks all day, munching on the plants. They are, however, considered to be a keystone species — they’re prey for many other species, especially crabs (we also eat them sometimes).

The authors wanted to find out what would happen should these periwinkles dine on algae that have absorbed microplastics. Prior research has shown that algae absorbing such products become enriched in hazardous chemicals and metals. Microplastics are porous and soak up these chemicals as they flute around (we’re dumping those chemicals there, too).

Microplastics.

Microplastic beads. They’re quite porous.
Image credits International Maritime Organization / Flickr.

The team’s hypothesis was that when a periwinkle eats the algae, it is also eating the hazardous materials present in the algae. In order to test if this results in any adverse changes for the snails, the team gathered a few periwinkles and brought them into the lab for testing. They also brought along a few crabs to use as predators.

They report that periwinkles which consumed the toxic materials did not react to the crabs in an expected way. Normally, upon spying the predator, the snails pull into their shells or try to hide in the surrounding environment. Those exposed to the toxic materials did not attempt to avoid capture, however, suggesting that they suffered nerve damage of some sort. This is likely due to the ingestion of heavy metals, the team adds.

They note that the levels of toxicity in the microplastics they used for the study were equivalent to those on a typical beach. The findings are thus broadly applicable in real-world conditions — and they point to major changes in the marine environment due to the microplastics we’ve introduced.

The paper “Microplastic leachates impair behavioural vigilance and predator avoidance in a temperate intertidal gastropod” has been published in the journal Biology Letters.

It will be illegal to boil lobsters alive in Switzerland

Swiss chefs will have to find more humane ways to cook lobsters. Officially, as of March, it will be illegal to boil lobsters alive in Switzerland. Instead, they should be stunned first. The decision was made after more and more evidence kept piling up supporting the fact that lobsters can indeed feel pain.

Credit: Pixabay.

Credit: Pixabay.

Local lawmakers voted an article stating “the practice of plunging live lobsters into boiling water, which is common in restaurants, is no longer permitted,” as part of a wider overhaul of the nation’s animal-protection law.

The Swiss take animal rights very seriously, having many laws in place that look after the physical and psychological well-being of animals, wildlife and pets alike. Some laws might even look silly to some, like the fact that it’s illegal to own just one guinea pig or parrot. Such animals are considered victims of abuse if they don’t regularly interact with others of their species. But for the Swiss, it’s a way to ensure an ethical, compassionate behavior towards animals.

Once the law comes into force, only after the lobster’s brain has been destroyed either with an electric shock or “mechanically” can the animal be boiled.

An urban myth responsible for a lot of suffering

In 2013, British researchers concluded shellfish, like crabs or lobsters, can feel pain.

This raised quite a few questions, as crabs are typically boiled alive. Since the crustaceans have a very primitive central nervous system, it has always been thought that they do not experience pain. The panic and struggle crabs experience when dived in boiled water has always been attributed to a reflex behavior, rather than pain-induced self-preservation.

The team led by Bob Elwood, an animal behavior researcher at the Queen’s University Belfast, devised two clever experiments that showed how crustaceans feel pain.

The scientists took 90 crabs and put them in a tank with two dark shelters. After most crabs selected their shelter of choice, one of the shelters was electrically charged. The scientists pulled out the crabs from the tank and after some rest inserted them back in. Most stuck with what they knew best, returning to the shelter they had chosen the first time around, only this time some unfortunate enough to choose the electrified shelter got shocked. When introduced to the tank for the third time, however, the vast majority of shocked crabs now went to the alternative safe shelter. Those not shocked continued to use their preferred shelter. This, says Elwood, strongly suggests that they learned to hate the shock.

In the second experiment, scientists presented crabs with two types of shell, one of which the animals are known to prefer, and gave them shocks when they chose the favored one. Whenever they were presented with a new shell, even the kind which they didn’t prefer, they chose it over the first one. This yet again suggests pain aversion.

“On a philosophical point, it is impossible to demonstrate absolutely that an animal experiences pain,” lead researcher Bob Elwood of the Queen’s School of Biological Sciences, was quoted as saying in a press release. “However, various criteria have been suggested regarding what we would expect if pain were to be experienced. The research at Queen’s has tested those criteria and the data is consistent with the idea of pain. Thus, we conclude that there is a strong probability of pain and the need to consider the welfare of these animals.”

According to professor Elwood, the most pressing concern are not domestic cooks and resturants but rather major food processing plants where animals are routinely dismembered before being killed. He believes crustaceans should be labeled with relevant welfare information so consumers make more informed choices.

Besides addressing cooking methods, the Swiss law also outlines new guidelines on transporting the animals from the oceans to, ultimately, your dinner table. According to the new law, “live crustaceans, including the lobster, may no longer be transported on ice or in ice water,” say the rules adopted by the government on Wednesday. “Aquatic species must always be kept in their natural environment.”

The new laws in the Alpine country also crack down on illegal puppy farms and automatic devices that punish dogs for barking. Hopefully, other countries will soon follow suit.

If you really enjoy a nice lobster dinner but would like to know what’s the most humane to kill them, the Australian RSPCA has a guide.

NM Museum of Natural History & Science

Scientists name 245-million-year-old Horseshoe crab after Darth Vader

 NM Museum of Natural History & Science

The horseshoe crab (left) and its namesake (right). Credit: NM Museum of Natural History & Science / Youtube.

The force is strong with this one. Paleontologists have discovered an ancient horseshoe crab species that bears an uncanny resemblance to a famous Sith lord. Aptly called Vaderlimulus tricki, this horseshoe crab is so old that dinosaurs and mammals weren’t even a ‘work in progress’ during its day. You could say this thick-headed arthropod was their father.

Horseshoe crabs are amazing animals. The earliest evidence of such creatures dates to a staggering 470 million years ago. Just so you can get an idea of how old these critters are, trees, as we familiarly know them today — a primary trunk, large height, a crown of leaves or fronds — didn’t appear on the planet until the late Devonian period, some 360 million years ago.

Amazingly, there are four species of horseshoe crabs still alive today. They haven’t changed in the last couple millions of years, which is why we call them living fossils. Another strange thing about them is that the crabs’ blood is a bright blue instead of the familiar red for vertebrates, since the arthropods use copper-based hemocyanin to transport oxygen instead of iron-based, red hemoglobin

A lot of people don’t know this but horseshoe crabs save millions of people every year. Instead of white blood cells that fight infections in our bodies, many invertebrates like the Atlantic horseshoe crab (Limulus polyphemus) employ amebocytes. A horseshoe crab’s amebocytes coagulate only one part per trillion of a bacterial contamination. The reaction also takes only 45 minutes instead of the typical two days in the mammalian equivalents. The chemical that enables this speedy coagulation is called — you’ve guessed it — coagulan, and it’s extremely important for testing medical equipment and vaccines. Without horseshoe crab-sourced amebocytes, many people would die from infections.  

Vaderlimulus tricki might not save lives like modern horseshoe crabs, but its presence looks like it caused a disturbance in the crab’s lineage. At least as far as appearance goes.

“Vaderlimulus, (unlike modern horseshoe crabs) has unusual body proportions that give it an odd appearance,” said lead author Allan J. Lerner from the New Mexico Museum, in a statement.

The ancient crab was found in Idaho, buried in rocks dated to around 245 million years old, which corresponds to the first period of the Mesozoic era, the Triassic. It belonged to the now extinct Austrolimulidae family, which included members that ventured beyond marine environments, expanding into freshwater ecosystems as well. This leap of faith might explain the bizarre appearance of Vaderlimulus tricki and its cousins, which had to adapt to new conditions.

Vaderlimulus tricki isn’t the only species, extinct or otherwise, named after Darth Vader. In 2003, Fernando Fernández dubbed a Colombian ant Adelomyrmex vaderi, perhaps because, like Vader, it towers over others of its kind, being one of the largest ants in its genus. The Dark Lord of the Sith lends his name to the Australian mite Darthvaderum greensladeae, named in 1996 by G.S. Hunt. Thricops vaderi is a species of housefly named by Jade Savage in 2003. Yes, entomologists seem particularly fond of Darth Vader. At least there’s a jellyfish named after Vader, too. Bathykorus bouilloni, where Bathykorus is Greek for “deep helmet”, sets itself apart by its tentacles, which are the biological equivalent of lightsabers.

Findings appeared in the journal Neues Jahrbuch für Geologie und Paläontologie.

Henderson Island was once regarded as one of the most pristine landscapes in the world. This makes this desolate sight from Henderson even more hurtful. Every day, some 27 new pieces of junk wash up on the island according to a new study. Credit: Jennifer Lavers/University of Tasmania.

Remote Island in the middle of the Pacific is the most plastic-littered place on Earth

Henderson Island was once regarded as one of the most pristine landscapes in the world. This makes this desolate sight from Henderson even more hurtful. Every day, some 27 new pieces of junk wash up on the island according to a new study. Credit: Jennifer Lavers/University of Tasmania.

Henderson Island was once regarded as one of the most pristine landscapes in the world. This makes this desolate sight from Henderson even more hurtful. Every day, some 27 new pieces of junk wash up on the island according to a new study. Credit: Jennifer Lavers/University of Tasmania.

Thousands of miles away from the nearest city, smack in the middle of the South Pacific Ocean, lies the Henderson Island. This island, part of the Pitcairn Islands and a UNESCO World Heritage Site, has never been permanently inhabited and only a few humans have ever made the trip by ship to set foot on it, usually scientists on research expeditions. Knowing this, Henderson ought to be one of the most pristine places on this planet. The sad reality, however, is that Henderson Island has the highest density of plastic trash ever reported in nature.

No escaping plastic pollution

“What’s happened on Henderson Island shows there’s no escaping plastic pollution even in the most distant parts of our oceans,” lead author Jennifer Lavers from the University of Tasmania said in a statement. “Far from being the pristine ‘deserted island’ that people might imagine of such a remote place, Henderson Island is a shocking but typical example of how plastic debris is affecting the environment on a global scale.”

According to the University of Tasmania team, huge quantities of plastic waste in all shapes and sizes have washed up along the years on Henderson. Every day, thousands of new tiny bits of plastic are thrown by tides on the white-sand beaches of the island.

Henderson Island is polluted with the greatest density of plastic in the world. The situation is so bad that hermit crabs use plastic debris for homes. Credit: Jennifer Lavers/University of Tasmania.

Henderson Island is polluted with the greatest density of plastic in the world. The situation is so bad that hermit crabs use plastic debris for homes. Credit: Jennifer Lavers/University of Tasmania.

For three months since May 2015, Lavers and colleagues lived on Henderson Island and documented all of the man-made trash there. Their estimates suggest there are over 37,661,395 pieces of anthropogenic trash which amount to 17.6 tons of plastic waste. This mass, however, represents only “1.98 seconds’ worth of the annual global production of plastic,” researchers wrote in the Proceedings of the National Academy of Science.

These stats are extremely worrisome and scary for a number of reasons. The report gives to show there’s no escaping human influence, i.e. trash, even in the remotest places on Earth. The oceans, like the land and atmosphere, is a unified environment which is why trash from San Francisco can wind up in the ocean and, eventually guided by currents, on a remote island such as Henderson. By some estimates, there may be some 5 trillion pieces of plastics and microplastics swirling around the world’s oceans. These wash up on shores across the planet where they litter and pollute the environment. Animals, both marine and land-based, eat these plastics causing them to suffer or die. Ultimately, humans can end up ingesting these plastics too since we’re at the top of the food chain.

Most of the items found on Henderson were largely disposable or single-use; things like razors, cigarette lighters, toothbrushes, etc. All of this trash doesn’t bode well with the island’s unique ecology, which includes ten endemic plant and four bird species. The image above with the hermit crab that uses a plastic container for a shell is most telling in this respect.

So, who’s to blame? Everyone basically. The paper doesn’t explicitly say this, but the millions of plastic debris on Henderson come from all over the world.

New study finds a myriad of applications for crab sugar

A review of recent research found that an unexpected mixture could do wonders for bone regeneration and wound healing.

This little guy could hold the future medical grafts within his shell. Image in Public Domain.

Chitosan is a type of sugar derived from shrimp and crab shell waste. It’s quite an amazing substance, used for its biocompatible, biodegradable, antibacterial, antifungal, analgesic and hemostatic (stops bleeding) properties. There are a number of potential applications which have researchers excited, but this review focuses on one thing in particular: medicine.

In a paper published in the journal Science and Technology of Advanced Materials, Duarte Moura from the Minho University in Braga, Portugal, found that combing chitosan with “nanofillers” makes the resulting material much stronger, without taking any medicinal properties away. They also found some success in combining bioactive glass nanoparticles with chitosan to develop synthetic bone grafts. Bioactive glass is a glass-ceramic biomaterial that binds well to physiological structures such as bone. Bone cells were found to grow relatively quickly and cover grafts made of bioactive glass and chitosan. Adding silver nanoparticles as nanofillers also gives the wound dressings antibacterial properties.

Graphene also came into the mix. In combination with chitosan, researchers can develop “nanocarriers” that can deliver drugs to target tissues, avoiding the negative side effects that conventional drugs can have on other tissues of the body.

Of course, this is pretty much the state of the art at the moment and a lot of research is still required. In particular, researchers still don’t fully understand how these composite materials degrade, which is particularly significant for medical applications. Also, more research is needed to understand how these composite materials interact with host tissues in the body and whether these materials can be sterilized using conventional methods. If this is not the case, then implementing them to medical treatment becomes much more complicated. But this is, without a doubt, an exciting field of research and one that holds great promise for the future.

“The vast opportunities shown by these materials, allied with their incredible nanotechnology potential, is expected to revolutionize the biomedical field in the near future,” the researchers conclude.

Journal Reference: Duarte Moura(*), Joao Mano, Conceicao Paiva, Natalia Alves — “Chitosan nanocomposites based on distinct inorganic fillers for biomedical applications”, Science and Technology of Advanced Materials Vol. 17. http://dx.doi.org/10.1080/14686996.2016.1229104
http://tandfonline.com/doi/full/10.1080/14686996.2016.1229104

 

 

 

Antarctica Yeti Crab Grows and Harvests its Own Food

Scientists have discovered and described the only known species of Yeti Crab that resides in Antarctica’s Southern Ocean. The crab, which has white fur-like bristles all over its body, survives in an extremely inhospitable environment, close to the hydrothermal vents that spew hot water in the freezing ocean.

Image via NOAA.

Sven Thatje from the University of Southampton first discovered the species in 2010, thanks to footage from a remotely-operated submersible vehicle (ROV). The ROV dove 8,500 feet (2,500 meters) below sea level and found that the yeti crab is the dominant species in the environment created by the hydrothermal vent. After that, they gathered specimens and studied them using genetic sequencing and computed tomography (CT) scanning. Their description of the creature’s strange morphology is published today (June 24) in the journal PLOS ONE. They named it Kiwa tyleri, after respected British polar and deep-ocean biologist Paul Tyler from Southampton University.

The Yeti Crab. Image via University of Southampton.

Thatje explains why this discovery is significant:

“Crabs and lobsters are very rare in Antarctic/Southern Ocean waters because of the unusually low seawater temperatures,” Thatje said. “A physiological limit to maintaining activities required for survival (ventilation, molting, mating) appears to exist at around 0.5 degrees C [32.9 degrees F].”

In other words, even though the crab is adapted to a cold environment and developed a stark white color and “hairy body”, it still can’t survive in very cold waters – that’s why they are so crowded together around the hydrothermal vent. A hydrothermal vent is a fissure in a planet’s surface from which geothermally heated water pumps up into the ocean, creating a hot pocket of water. In 2012, an expedition found hundreds of crabs clumped up one over another.

“They’re literally, in places, heaped up upon each other,” Alex Rogers, a professor of zoology at Oxford University who led the expedition to the East Scotia Ridge, said in 2012. Photographs taken by Rogers’ team show 600 crabs per square meter.

It seems like the entire species inhabits only a few cubic meters, which raises the question: if so many crabs are clumped up together, what do they eat? The answer was surprising: the yeti crab uses its “fur” to harvest bacteria, which it grows and then relies on for nutrition.

“The Antarctic Yeti Crab is trapped in its warm-water hydrothermal vent site by the cold polar waters of the surrounding deep-sea. The species has adapted to this very limited sized habitat — of a few cubique metres in volume — by occurring in highly-packed densities and by relying on bacteria they grow on their fur-like setae [stiff bristles] for nutrition,” Dr Thatje said in a press release.

boiled crab feel pain

Crabs and other shellfish feel pain. Opens ethical discussion

boiled crab feel painA new study from researchers at Queen’s University Belfast, UK, found that indeed shellfish, like crabs or lobsters that are typically cooked alive in horrid conditions, feel pain as well. The findings raise significant ethical discussions, warning the food and fish industry of its ill ways of killing live seafood.

“On a philosophical point, it is impossible to demonstrate absolutely that an animal experiences pain,” researcher Bob Elwood of the Queen’s School of Biological Sciences, was quoted as saying in a press release. “However, various criteria have been suggested regarding what we would expect if pain were to be experienced. The research at Queen’s has tested those criteria and the data is consistent with the idea of pain. Thus, we conclude that there is a strong probability of pain and the need to consider the welfare of these animals.”

Crabs are typically boiled alive in a tank, however since the crustaceans have a very primitive central nervous system, it has always been thought that they do not experience pain. The panic and struggle crabs experience when dived in boiled water has always been attributed to a reflex behavior, not at all to pain-induced self preservation.

“In contrast to mammals, crustaceans are given little or no protection as the presumption is that they cannot experience pain. Our research suggests otherwise,” Professor Elwood said.

“More consideration of the treatment of these animals is needed as a potentially very large problem is being ignored.”

To distinguish between reflex and actual pain the researchers devised a simple, but ingenious experiment. The scientists took 90 crabs and put them in a tank with two dark shelters. After most crabs selected their shelter of choice, one of the shelters was electrically charged. The scientists pulled out the crabs from the tank and after some rest inserted them back. Most stuck with what they knew best, returning to the shelter they had chosen first time around, where those that had been shocked on first choice again experienced a shock. When introduced to the tank for the third time, however, the vast majority of shocked crabs now went to the alternative safe shelter. Those not shocked continued to use their preferred shelter.

“Having experienced two rounds of shocks the crabs learned to avoid the shelter where they received the shock,” Professor Elwood said.

“They were willing to give up their hideaway in order to avoid the source of their probable pain.”

With this in mind, crabs, lobsters and other shellfish and crustaceans may experience the world more like us than we might have thought. Findings were reported in a paper published in the Journal of Experimental Biology.

via Discovery

Wrapped in a free for all tug of war, the hermit crabs stack as each is looking to displace its shell for a more spacious one.

Hermit crabs socialize in order to back stab their neighbor and steal their ‘homes’

There are around 800 hermit crab species living in the ocean. These crustaceans like to mind their own business and are rarely seen alongside one another, hence their species’ name. The dozen or so terrestrial hermit crab species, however, are forced to engage socially in order to survive. Their social pattern reveals a selfish agenda, though, after a recent study by biologists at Berkeley University found a vicious behavior – the land hermit crabs gather and kick other crabs out of their shell, in order to move in it.

Wrapped in a free for all tug of war, the hermit crabs stack as each is looking to displace its shell for a more spacious one.

Wrapped in a free for all tug of war, the hermit crabs stack as each is looking to displace its shell for a more spacious one.

These hustling hermit crabs have been forced to adapt this way, though one might suggest that evolution could have brought them down a more altruistic path. Typically, ocean hermit crabs use empty snail shells that are abundant through out as shelter and egg deposits. On land however, the only empty snail shells available are the few that happen to wash ashore. Pushed by scarcity, the terrestrial hermit crab adapted and developed a unique trait, distinct from their ocean dwelling cousins – they’re the only ones that hollow out and remodel their shells, sometimes doubling the internal volume.

Even with this impressive skill, however, the hermit crab still winds up in trouble since sooner or later it will outgrow its shell. In order to survive, the hermit crabs developed a sort of sacrificial social gathering. Thus, as three or more crabs gather around, others flock by the dozens as well, eager to trade up. Curiously, they first line up in a sort of conga line, smallest to largest by the shell, each holding on to the crab next to him. As they trade shells, most of the time the largest of the group gets more than he bargained for when he first joined, as he gets wrenched from its shell .

“The one that gets yanked out of its shell is often left with the smallest shell, which it can’t really protect itself with,” said Mark Laidre, a UC Berkeley Miller Post-Doctoral Fellow, who is in the Department of Integrative Biology. “Then it’s liable to be eaten by anything. For hermit crabs, it’s really their sociality that drives predation.”

Hermit crab shell

A marine snail shell newly vacated by its gastropod owner (left) and a shell that has been remodeled by a hermit crab.

If they can modify shells themselves, why trick their brethren in such a despicable manner? Well, in an experiment in which Laidre and colleagues pulled crabs from their homes and instead offered them newly vacated snail shells, the researchers found that only the smallest hermit crabs took advantage of new shells, as they’re the only ones to fit in and thus begin the remodeling process. The rest perish.

Laidre believes this behavior to be an excellent example of how niche construction leads to unusual traits, like this out of the ordinary socialization in an otherwise solitary animal.

“No matter how exactly the hermit tenants modify their shellters, they exemplify an important, if obvious, evolutionary truth: living things have been altering and remodeling their surroundings throughout the history of life,” wrote UC Davis evolutionary biologist Geerat J. Vermeij in a commentary in the same journal.

Findings were documented in the journal Current Biology.

source: Berkeley Newsroom

120 million crabs hit the streets

Image by Lilolebob.

Every year, around this time of year, more than 100 million determined crabs take to the streets in a massive attempt to get to their spawning grounds as soon as possible; as a result, they literally flood the streets in Christmas island, covering the streets and forcing rangers to divert traffic and use some quite creative methods of protecting the crustaceans.

Photo by Ian Usher.

However, despite the absolutely huge number of crabs, there have been no reports of violence, from any one of the islands 1200 inhabitants. “It is difficult to see crabs in the houses,” one local resident told BBC Brasil. However, the efforts local rangers have been sustaining are nothing short of laudable; they constructed plastic bridges and fences to keep them from more populated areas and even help them across difficult areas (I don’t know, but I’m guessing difficult urbanized obstacles).

At 135 square km and located 370 km off of Indonesia, this Australian territory is often called the “Galapagos of the Indian Ocean” for its diversity of both plant and animal life. It’s also home to 14 different species of crabs, including the coconut crab, the largest invertebrate in the world. The efforts I mentioned earlier are even more impressive taking into account the 1.5 million people who come to see the amazing wildlife display each year.