Crabs, lobsters and shrimp now have a family tree dating 500 million years

APRIL 24, 2019

by Chrystian Tejedor, Florida International University

Researchers have for the first time traced the roots of crabs, lobsters and shrimp to create the family tree of crustaceans people love to eat.

The tree shows the 450-million-year evolution of these 10-legged decapods, when lobsters and crabs each diversified from a single evolutionary origin. Groups of shrimpevolved earlier.

The findings are part of a massive family tree project where researchers resolved the deep evolutionary relationships between crabs, shrimp and lobsters. The discoveries made by analyzing more than 400 genes from 94 species could also inform conservation policies to ensure their longevity.

"Understanding the origins of biodiversity across half a billion years in groups that are extremely ecologically and economically important is fascinating," said FIU marine sciences professor Heather Bracken-Grissom, the anchor author of the study. "This is extremely important since studying and preserving biodiversity needs to be at the forefront of our efforts in the biological sciences and across humanity"

The boom of diversification for crabs, lobsters and shrimp may coincide with the spread of modern reef-building corals, Bracken-Grissom said. It is possible the emergence of reef-building corals provided new habits for decapods to colonize and diversify, leading to the emergence of several new lineages after the mass extinction of life on Earth 250 million years ago.

While the study produced the largest amount of genetic information about decapods, more work remains to be done including the addition of more species to better understand species-level relationships. The researchers hope the newly generated genomic resources will be used by others interested in decapod crustaceans for years to come.

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Seeing through the eyes of a crab

New research provides insight into the visual world of a crustacean

Date:  July 16, 2018

Source:  Society for Neuroscience

Crabs combine the input from their two eyes early on in their brain's visual pathway to track a moving object, finds new research published in JNeurosci. This study of adult male crabs from Argentina's Atlantic coast provides insight into the visual world of a crustacean.

The widely spaced eyes and visually guided behaviors of the crab Neohelice granulata suggest this highly social predator may compute visual parameters of moving targets by combining input from both eyes, but it is unclear where and how the two sources of visual information are merged and processed.

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Lobsters and crabs should not be boiled alive, say campaigners

By Paul Rincon

Science editor, BBC News website

More than 50 high-profile campaigners and celebrities have called for stronger protection to prevent lobsters and crabs being cooked alive.

They have signed a letter urging Environment Secretary Michael Gove to categorise the crustaceans as sentient organisms in a new Animal Welfare Bill.

The organisers point to mounting scientific evidence that shows the animals can feel pain.

Signatories include presenter Chris Packham and comedian Bill Bailey.

They also include representatives from the RSPCA and the British Veterinary Association.

Establishing whether some animal groups feel pain can take years of scientific research.

But there has been considerable scientific research on sentience in decapods - the crustacean group that includes lobsters and crabs - since Parliament passed the Animal Welfare Act in 2006.

Maisie Tomlinson, from the campaign group Crustacean Compassion, which organised the letter, told BBC News: "It's really not acceptable to be boiling animals alive, to be cutting them up alive.

"All the evidence out there at the moment points to the notion that they're capable of experiencing pain."

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In Your Face! Male Crabs Gloat with 'Victory Dance'

By Mindy Weisberger, Senior Writer | November 11, 2017 08:50am ET

Some male animals are known for busting a move in elaborate mating dances to woo prospective mates. But some crab males perform a special dance for the males they've just defeated in combat, to discourage them from coming back for more, according to a new study.

Scientists had previously observed that after two male crabs tussled over a female, the victor would perform a type of "dance move" directed toward the defeated male, rather than toward the female. They suspected the motion was meant intimidate the crab that had lost the fight, but they did not know for sure.

Recently, researchers put that idea to the test with observations of Perisesarma eumolpe, a colorful type of mangrove crab native to southeast Asia. They analyzed how rivals responded to dances, and noted that when a victorious crab performed a taunting strut, the loser was more likely to slink away in defeat. [Strange Love: 10 Animals with Truly Weird Courtship Rituals]

Read on  

Two Buddhists fined £15,000 for releasing crustaceans into sea

Saturday 23 September 2017 11.31 BST Last modified on Monday 25 September 2017 09.54 BST

Two Buddhists who released £5,000 worth of crustaceans into the Channel as part of a religious ceremony have been fined almost £15,000 for causing “untold damage” to the environment.

Zhixiong Li and Ni Li helped throw live crabs and lobsters into the sea off Brighton as part of a “life release” ceremony in 2015, a court has heard.

The pair were part of a group of almost 1,000 people celebrating the visit of the Taiwanese Buddhist master Hai Tao.

Their ritual was performed in the belief that returning animals to the wild is good karma. But because the crustaceans were not native species, they threatened other marine life and government agencies had to spend thousands of pounds in an attempt to recapture the shellfish, offering fishermen a bounty to reel them in.

In the first case of its kind, Zhixiong Li, 30, an estate agent, and Ni Li, 33, a City banker, both from London, admitted wildlife offences and were fined.

Both defendants pleaded guilty to releasing non-native species into the wild at Brighton magistrates’ court this week.

Joseph Miller, prosecuting for the Marine Management Organisation, said the case first came to light after a Brighton fisherman captured some of the foreign shellfish in June 2015.

CCTV footage from Brighton marina showed the group of Buddhists chartering three boats, having also bought more than £2,500 worth of native crabs and lobsters from Brighton and Newhaven Fish Sales at Shoreham harbour.

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Watch cuttlefish apparently pretending to walk just like crabs

31 May 2017


By Sandrine Ceurstemont

Cuttlefish have been caught on film walking like crabs by moving their tentacles in novel ways.

Kohei Okamoto at the University of the Ryukyus in Okinawa, Japan, and his team first spotted pharaoh cuttlefish (Sepia pharaonis) displaying the unusual behaviour while feeding them in the lab.

“We were surprised to see how closely they resemble hermit crabs,” says Okamoto.
  
The molluscs would raise their front arms while they bent their other legs, as if they had joints, while quickly moving them up and down independently. Certain parts of their skin also darkened.

The team later filmed the cuttlefish making the same arm movements during experiments in tanks containing small fish that could be prey (see video below).

Cuttlefish are known mimics. They can change colour, texture, skin patterns and even posture instantly to blend in with their surroundings. They can also make complex movements with their arms, not only to help with camouflage but also to startle or lure prey or grip their partner while mating.



Read more and watch video

Scientists reveal game of thrones in crab world

January 25, 2017 

Crabs that invade smaller crab species' habitat overpower and evict incumbents from their burrows, but the two species ultimately co-exist and join forces against other invading crabs in a game of thrones once they establish territorial boundaries, new research finds. 

Lead researcher Huon Clark from ANU said the finding overturns the theory that interactions between species of fiddler crabs result in the dominant species pushing the weaker ones out of a habitat.

"There appears to be mutual benefits for these different crabs to live alongside each other in the same habitat," said Mr Clark, a PhD student at the ANU Research School of Biology.

"It reduces the competition for mates for the larger crabs, which in turn offer protection to smaller crabs against bigger crabs seeking to take over their burrow.

"We found that while the smaller species of fiddler crab is impacted in a negative way by the arrival of the larger species, they can co-exist quite harmoniously once the larger species settles in."

Mr Clark said climate change and habitat loss may result in more species of fiddler crabs interacting and sharing territories that were previously the domain of only one species.

Read more at: 

New crab species shares name with two 'Harry Potter' characters and a hero researcher

Date: January 23, 2017
Source: Pensoft Publishers

While not much is known about the animals living around coral reefs, ex-Marine turned researcher Harry Conley would often take to the island of Guam, western Pacific Ocean, and dig deep into the rubble to find fascinating critters as if by magic learnt at Hogwarts. Almost 20 years after his discoveries and his death, a secret is revealed on the pages of the open access journal ZooKeys -- a new species and genus of crab, Harryplax severus.

Having dug as deep as 30 m into Guam's coral reef rubble, Harry Conley collected many specimens which stayed in his personal collection until the early 2000's when Dr. Gustav Paulay, currently affiliated with the University of Florida, handed the specimens to the second author of the present study, Dr. Peter Ng, National University of Singapore, which resulted in many discoveries and publications. Among the lot, however, were two unusual specimens which were not studied until much later. Only recently did Dr. Peter Ng and his colleague at the National University of Singapore and lead author of the paper, Dr. Jose Christopher E. Mendoza, discover that they represent not only a new species, but also a new genus.



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Oysters And Crabs ‘Stuck In The Middle’

May 12, 2014

By Angela Herring, Northeastern University

Northeastern University ecologist David Kimbro claims to have watched a lot of TV growing up, particularly The Brady Bunch. “You could kind of get a flavor for how an episode was going to turn out based on how Jan or Peter were faring—you know, the middle kids,” said Kimbro, an assistant professor in the Department of Marine and Environmental Sciences.

He and his colleagues—associate professor Jon Grabowski and assistant professor Randall Hughes, ecology experts with labs at Northeastern’s Marine Science Center—think a similar pattern shows up in oyster reefs, where the behavior of the “middle child” in the predator-​​prey food chain plays a strong role in determining how the reef as a whole will fare. New research from the team, published online on Tuesday in the journal Ecology Letters, gives that hunch even more support.

The work complicates the evolution of a paradigm that has pervaded ecology since the 1960s, namely that the species at the top of the food web dic­ate the welfare of the entire system simply by eating.

For instance, observations in the Aleutian Islands in the 1970s showed that when sea otters were doing well, the nearby kelp forests below the ocean’s surface also thrived. This was due, theory said, to the fact that the otters’ feeding patterns naturally managed the sea urchin population, which feeds on kelp.

Fast-​​forward four decades and one sees a large body of evidence indicating that predators do more than eat; they frighten too. In the early 2000s, Grabowski showed that having a predatory fish scare the middle child has the same effect as predation itself. Like­wise with the sea otters—just swimming around scares the urchins enough to send them into hiding and stop eating kelp.

Read more at

Crazy Cretaceous Find: Intersex Crabs

DENVER — It's a crustacean conundrum: Why did some Cretaceous crabs sport both male and female characteristics?

The answer is unknown, but new fossil discoveries reveal that intersex crabs were a small but persistent part of the population in South Dakota during the Cretaceous Period — and a parasitic barnacle may have been to blame.

The fossils, excavated in South Dakota shale, are of Dakoticancer overanus, a quarter-size crab that lived about 68 million years ago. At the time, North America was split in half by the Western Interior Seaway, a shallow sea that harbored strange creatures like the toothy mosasaur, an apex predator that evolved from land-living lizards.

Read more

Supersized Crabs Bad News for Seafood Lovers

 Marc Lallanilla, Assistant Editor

Date: 08 April 2013 Time: 03:41 PM ET

The giant crabs are coming. And they're hungry.

Researchers at the University of North Carolina's (UNC) Aquarium Research Center have found that higher atmospheric levels of carbon dioxide — a greenhouse gas that's linked to global warming — are also causing crabs to grow to bigger, faster and stronger, according to the Washington Post.

As the oceans absorb significant amounts of atmospheric carbon dioxide, ocean water becomes more acidic and carbon-rich, and these higher levels of carbon are giving rise to the supersized crabs.

Continued:  http://www.livescience.com/28540-crabs-oysters-carbon.html

Invasive Crabs Help Restore Marsh

Douglas Main, Staff Writer

Date: 04 April 2013 Time: 05:35 PM ET

You may not be able to fight fire with fire, but fighting crabs with crabs may have some merit. 

Researchers studying the imperiled marshes of Cape Cod were recently surprised to discover that a section of the marsh was coming back, sprouting a "veneer of cordgrass," according to a news release describing the study. In the places where this impressive turnabout was seen, the researchers also beheld a most unlikely cause for celebration: invasive green crabs.

Further research found these crabby immigrants were feasting upon the native marsh crab, which has overpopulated the area and eaten massive quantities of marsh grasses, leading to erosion and habitat destruction (silly marsh crabs, destroying their own eponymous environs).

Humans are largely to blame for this explosion of marsh crab, by killing their predators, including fish. And humans are also to blame for the arrival of the invasive green crab. Usually two wrongs don't make a right, but it appears, for now, the invasive greens are helping the marsh come back in two ways: Besides eating the natives, the invasive crustaceans also appear to act like "scarecrows," leading the native crabs to eat less grass.

Find the study here.

http://www.livescience.com/28461-invasive-crabs-help-restore-marsh.html

Crabs and lobsters tagged in Orkney spawning study

Researchers in Orkney are to fit tags to thousands of crabs and lobsters over the next four years as part of a study to ensure stocks remain high.

It will monitor spawning and examine how fishermen and the wave and tidal energy industry can work in harmony.

The research will also help establish that supplies are sustainable.
Crabs and lobsters caught in the cold, clean waters around Orkney are renowned for their quality and are popular with consumers across Europe.

The study is being conducted by The Crown Estate, along with Marine Scotland and Orkney Sustainable Fisheries Ltd.

It will be undertaken by local fishing fleets and marine researchers, under the guidance of scientists at Heriot-Watt Orkney Campus.

The information gathered will also prove valuable to the developers of wave and tidal energy schemes, helping them to avoid the most sensitive sites when installing their devices.

Ronnie Quinn, The Crown Estate's head of energy and infrastructure for Scotland, said: "Knowledge is essential in understanding existing marine users and emerging energy industries.

"The Crown Estate is committed to working with the fishing industry and we are delighted to be embarking on this work, which will be vital in aiding our understanding of how the Pentland Firth and Orkney waters marine energy projects can be progressed in a way which gives a maximum benefit to the local communities of Caithness and Orkney."

Read on:  http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-21270461

Further evidence crabs and other crustaceans feel pain

Scientists have found further evidence that crustaceans feel pain.

A study has revealed that the shore crab, a close relative of the species we use for food, responds to electric shocks and then goes on to avoid them.

Previous research has shown that prawns and hermit crabs also react to painful situations.

The scientists say the findings suggest the food and aquaculture industry should rethink how it treats these animals.

The work is published in the Journal of Experimental Biology.

Professor Bob Elwood, from Queen's University Belfast, told the BBC's Science in Action programme: "I don't know what goes on in a crab's mind.... but what I can say is the whole behaviour goes beyond a straightforward reflex response and it fits all the criteria of pain."

Shell shocked

Pain is a subjective experience and studying it in animals - especially invertebrates such as crabs - is not easy.

The researchers placed the crabs in an arena and studied how the responded to electric shocks

But Prof Elwood designed an experiment to assess how crustaceans respond to potentially painful situations.

Continued:  http://www.bbc.co.uk/news/science-environment-21044077

Sea food – and eat it! Fish rain in Vladivostok

Typhoon Bolaven led to significant disruption in the Far East of Russia this week - closing bridges, downing power cables, halting ferries, briefly causing delays on the Trans-Siberian Railway, and damaging some property.  

But then - as these extraordinary pictures showed - it washed up a feast of delicious sea food on beaches in Lazurnaya Bay. 

On the morning of 31 August the popular Shamora beach close to Vladivostok was literally teeming with thousands upon thousands of molluscs and crabs, most of them very tasty ones. 

'Now we know what 'manna from heaven' means,' wrote a local girl Svetlana in her blog. 

'And this is at Shamora where for the last 30 years there was nothing else edible but shashlyk ( barbecue ) .'

Dozens of beach-side cafes now had something else to cook. Swarms of locals hurried to the beach to collect tasty seafood for the weekend. 

Almost all the shellfish were alive but it was useless to carry them back to the sea - the storm-powered waves threw them back on the beach again almost immediately. People had nothing else to do but to collect them to cook for a free lunch - or take nice pictures with beautiful big crabs. 

Some locals brought their rubber boats and entertained their children making pools with live molluscs.

Continued:  http://siberiantimes.com/weird-and-wonderful/news-and-features/news/sea-food-and-eat-it-fish-rain-in-vladivostok/

Strange Deep-Sea Crabs May Color-Code Their Food

What good is color vision in the dark of the deep sea? For some crabs, an ability to see blue and ultraviolet light may mean the difference between chowing down on a good meal versus a toxic one.

A new study published today (Sept. 6) in the Journal of Experimental Biology finds that some seafloor, or benthic, crabs can see in color. But the crustaceans live in darkness of the deep Caribbean where sunlight does not penetrate, making their sensitivity to blue and ultraviolet light mysterious.

The reason for the color vision, however, may be explained by the concurrent discovery of bioluminescent deep-sea plankton in this environment, which glow blue when they bump against objects along the seafloor. It's possible that the crabs see this blue glow as a sign of a hearty meal, said study researcher Tamara Frank, a biologist at Nova Southeastern University in Florida.


Continued:  http://www.livescience.com/22974-deep-sea-crabs-vision-bioluminescence.html

'The Hoff' crab is new ocean find

UK scientists have found prodigious numbers of a new crab species on the Southern Ocean floor that they have dubbed "The Hoff" because of its hairy chest.

The animal was discovered living around volcanic vents off South Georgia.

Great piles of the crabs were seen to come together.

The creature has still to be formally classified, hence the humorous nickname that honours the often bare-chested US actor David Hasselhoff.

It is, however, a type of yeti crab, said Professor Alex Rogers who led the research cruise that found the animal, and it will be given a formal scientific name in due course.

Yeti crabs were first identified in the southern Pacific and are recognised for their hairs, or setae, along their claws and limbs that they use to cultivate the bacteria which they then eat.

But the new species found around the vents that populate the East Scotia Ridge are slightly different in that they exhibit long setae on their ventral surface - on their undersides.

"Their nickname on the cruise ship was the 'Hasselhoff crab', which gives you some idea of what they look like," explained Dr Rogers from Oxford University's Department of Zoology.

"The crab occurs in staggering densities. It is just incredible to see these animals literally lying in heaps around the diffuse flow of these vents.

"In places, they reached as many as 600 individuals per square metre."

The Hoff crab is just one of a number of species new to science to come out of the cruise, which also included researchers from the University of Southampton, the National Oceanography Centre and the British Antarctic Survey.

The team reports novel types of starfish, barnacles, sea anemones, and even an octopus - all living some 2,500m down.

The cruise employed the UK deep-diving robotic submersible, Isis, to investigate the slowly spreading ridge near Antarctica.

It is dotted with hydrothermal vents - cracks in the volcanic rock where mineral-rich, hot waters gush from below the seabed to sustain an extraordinary array of organisms.

By Jonathan AmosScience correspondent, BBC News

Read more at:  http://www.bbc.co.uk/news/science-environment-16394430

How Crabs Avoid Getting Eaten

Despite their simple compound eyes crabs have evolved a smart way to tell the difference between friend and foe, new scientific research has revealed.

Scientists from The Vision Centre have found that fiddler crabs quickly learn to recognize if an approaching creature is a threat, a mate or a harmless passer-by – according to its direction of approach.

“Fiddler crabs have extremely poor sight, with no depth perception and no ability to see in detail,” says Ms Chloe Raderschall, a researcher from The Vision Centre and The Australian National University. “In a situation where every ‘blob’ that moves in the environment can be a threat, they have to strike a balance between succumbing to paranoia – and ending up as bird feed.

“Crabs achieve this through a process called habituation where they learn from repeated events to differentiate threats from harmless objects. Humans too use habituation: for instance we learn to ignore the sound from an air conditioner once we grow accustomed to it.

‘We found that crabs have a very selective and finely tuned habituation response – instead of relying solely on the physical appearance of an object, they associate the object with its past behavior in their living environment, such as its direction of approach.”

In the study, the researchers used dummy predators to approach groups of fiddler crabs from two different compass directions.

“We did two dozen runs of a dummy approaching from direction A without attacking the crabs, and within five runs, the crabs started to ignore it,” Ms Raderschall explains. “When we switched to another dummy coming from direction B, the crabs were scared witless and headed straight to their burrows.”

When the researchers switched back to direction A, they found the crabs did not attempt to escape, indicating that they clearly distinguish between the dummies approaching from the two directions, she says.

“As both dummies were identical and there was no difference in the timing of their movements, we conclude that the crabs used the direction of approach to determine whether an approaching object was a threat or not.”

Ms Raderschall explains that this finding confirms that crabs have an extremely specific habituation response. This contradicts previous assumptions found in most text books that habituation is a simple learning mechanism based mostly on physical appearances.

“Their identification of a dangerous or harmless object is closely associated with their memory of how the object behaves, rather than how it looks.

“Apart from very simple visual cues, they don’t really have other ways to detect predators, and this study provides clues as to how animals with relatively poor vision can adapt and survive over time.”

The paper ‘Habituation under natural conditions: model predators are distinguished by approach direction’ by Chloe A. Raderschall, Robert D. Magrath and Jan M. Hemmi was published on 23 November 2011 in The Journal of Experimental Biology.

The study was conducted in the Research School of Biology at The Australian National University.

The Vision Centre is funded by the Australian Research Council as the ARC Centre of Excellence in Vision Science.

Source: redOrbit (http://s.tt/14ewu)
http://www.redorbit.com/news/science/1112429177/how-crabs-avoid-getting-eaten/index.html