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|Giant Squid - Architeuthis dux|
|Tweet Topic Started: Jan 9 2012, 03:39 PM (9,678 Views)|
|Taipan||Jan 9 2012, 03:39 PM Post #1|
Giant Squid - Architeuthis dux
Species: Architeuthis dux
Description & Behavior
The giant squid, Architeuthis dux (Steenstrup, 1857), of the family Architeuthidae, is possibly the largest known cephalopod, the largest known mollusk and, likely, the largest invertebrate ever known to exist (except for possibly the colossal squid, Mesonychoteuthis hamiltoni which may have a mantle length nearly twice the size of the giant squid!). These squid can reach up to 18 m in total length, which includes the head, body, arms, and two long feeding tentacles, which are much longer than the rest of the body reaching 10-12 m in length. Giant squid average 11-14 m, and they are also commonly found 6-9 m in length. They can weigh up to 900 kg, but average 455 kg or less.
The giant squid have the largest eyes out of any animal in the world. They can be as large as a dinner plate. They function to detect the small amounts of light in the deep (including bioluminescent light).
They have 2 rows of suckers on the inner surface of their 8 arms and 2 tentacles. The suckers are sub-spherical cups lined with sharp, finely serrated rings of chitin in four longitudinal rows. These tentacular clubs are divided into three distinct regions: carpus, manus and dactylus. The manus of the giant squid has enlarged suckers along two medial rows. The suckers on the tentacles and arms are typically no larger than about 5-5.5 cm. The carpal region has a dense cluster of suckers, in 6-7 irregular, transverse rows. At the base of the arms, they have a parrot-like beak characteristic of other cephalopods.
The giant squid also has small fins at the rear of the mantle used for locomotion. The gentle, rhythmic pulses of water pushed out of the mantle cavity through the funnel propels the squid through the water; they can also move quickly by expanding the mantle cavity to fill with water then contracting muscles to jet water through the funnel.
Giant squid breathe using 2 large gills that rest inside the mantle cavity.
Like other squid species, giant squid contain dark ink used to deter predators. They have a sophisticated nervous system and complex brain. The circulatory system is closed, which is a distinct characteristic of the squid.
Because of their nervous system and large brain, they are of great interest to scientists, though they have never been observed in their natural habitat until very recently (see the photo above and the National Geographic link under References). Therefore, little is known about their behavior and interaction. They are believed to be solitary hunters; only individual giant squids have been caught in fishing nets.
World Range & Habitat
Giant squid are wide-ranging usually found near continental and island slopes from the North Atlantic Ocean, especially Newfoundland, Norway, northern British Isles and the oceanic islands of the Azores and Madeira to the South Atlantic in southern African waters; the North Pacific around Japan, and the southwestern Pacific around New Zealand and Australia. They are circumglobal in the Southern Ocean. Specimens are rare in tropical and polar latitudes.
Worldwide giant squid distribution based on recovered specimens
Feeding Behavior (Ecology)
Recent studies have shown that giant squid eat deep-sea fishes and in other squid species.
Giant squid capture prey using the 2 feeding tentacles that grip their victims with serrated the saw-like sucker rings, called the tentacle clubs, on the ends. When the prey is in their grasp, they bring it toward the powerful beak, then use the radula with its small, file-like teeth to shred the prey before it reaches the esophagus.
Sperm whales and sleeper sharks such as Somniosus pacificus are the two known predators of adult giant squid. Juveniles are preyed on by deep sea sharks and fishes.
Little is known about giant squid reproduction. Females produce large quantities of eggs, in some cases more than 5 kg, that average 0.5-1.4 mm long and 0.3-0.7 mm wide. Females have a single median ovary in the posterior end of the mantle cavity and paired convoluted oviducts where mature eggs pass exiting through the oviducal glands, then through the nidamental glands. Like other squid species, these glands produce a gelatinous material used to keep the eggs together once they are laid.
It is thought that giant squids reach sexual maturity at about 3 years; males reach sexual maturity at a smaller size than females. Like other squid, it is thought that the two ventral arms are modified to transfer spermatophores to the female. As in most other cephalopods, the single, posterior testis produces sperm that move into a complex system of glands that manufacture the spermatophores. These are stored in the elongate sac, or Needham's sac, which terminates in the penis from which they are expelled during mating. The penis is elongate and extends anteriorly beyond the mantle opening. Mating in the giant squid has not been observed, so the exact role of the penis is uncertain; however, some females have been found with spermatangia (sperm-containing sacs of the spermatophore) embedded in the tissue around the bases of the arms and the head.
The giant squid, Architeuthis dux, could be an essential part of the food web as they are preyed on by deep-diving whales (e.g., sperm whales) or a keystone species in their deep habitats.
Myths & Stories
"In 1965, a Soviet whaler watched a battle between a squid and a 40 ton sperm whale. In the case of this battle, neither was victorious. The strangled whale was found floating in the sea with the squid's tentacles wrapped around the whale's throat. The squid's severed head was found in the whale's stomach.
In the 1930's a ship owned by the royal Norwegian Navy called the Brunswick was attacked at least three times by the giant squid. In each case the attack was deliberate as the squid would pull along side of the ship, pace it, then suddenly turn, run into the ship and wrap its tentacles around the hull. The encounters were fatal for the squid as its grip on the ship's steel surface would come loose, and the animal slid off and fell into the ship's propellers."
These stories suggest that giant squid may be aggressive animals, but again because few observations have been made, this is unknown. Deep sea exploration technology will enable researchers to study this animal more closely.
There are many stories, myths, and mysteries about the giant squid, and it has been called the last great monster of the sea. Another story: "One night during World War II a British Admiralty trawler was lying off the Maldives Islands in the Indian Ocean. One of the crew, A.G. Starkey, was up on deck, alone, late at night fishing, when he saw something in the water. 'As I gazed, fascinated, a circle of green light glowed in my area of illumination. This green unwinking orb I suddenly realized was an eye. The surface of the water undulated with some strange disturbance. Gradually I realized that I was gazing at almost point-blank range at a huge squid.' Starkey walked the length of the ship finding the tail at one end and the tentacles at the other. The ship was over one hundred and seventy five feet long."
Edited by Taipan, Oct 27 2012, 05:26 PM.
|Taipan||Jan 11 2012, 01:45 PM Post #2|
|Taipan||Jan 11 2012, 01:45 PM Post #3|
|Taipan||Jan 11 2012, 01:46 PM Post #4|
Gruesome habits of the giant squid
29 July 2005
NewScientist.com news service
ENSHRINED in myth as ferocious beasts that upturned boats to munch on sailors, giant squid could have a diet that is even less palatable in reality: Architeuthis dux may indulge in cannibalism.
Identifying the prey of A. dux has not been easy because the squid finely macerate their food, the digestive systems of most specimens studied have been empty, and none has ever been examined alive.
Now Bruce Deagle of the University of Tasmania, Australia, and his team have analysed the gut contents of a male giant squid caught by fishermen off the west coast of Tasmania in 1999. Among the slurry of macerated prey, they found three tentacle fragments and 12 squid beaks. The beaks could not be unequivocally identified, but all of the squid DNA in the slurry, and the tentacle fragments, was found to be that of A. dux (Journal of Heredity, vol 96, p 417). "This strongly suggests cannibalism," says team member Simon Jarman of the Australian Antarctic Division in Kingston, Tasmania. The only other prey species identified was a fish, the blue grenadier.
Steve O'Shea and Kat Bolstad at the Auckland University of Technology in New Zealand were the first to find evidence of cannibalism in A. dux, in a female caught in New Zealand waters. They published their findings in the New Zealand Journal of Zoology last year. But O'Shea suspected the cannibalism was accidental.
"The male giant squid has to use a puny 15-gram brain to coordinate 150 kilograms of weight, 10 metres of length and a 1.5-metre-long penis," he says. "He physically plunges this penis into the female's arms, which are rather unfortunately right next to her beak. Because he is coordinating so much with so little, I think occasionally bits get chewed off when they inadvertently get too close to the beak."
However, the Tasmanian specimen is male. And other large squid, such as the jumbo squid, Moroteuthis ingens, are known to eat members of their own species, Jarman points out. The team therefore thinks the cannibalism is likely to be intentional. "It is interesting that cannibalism has been documented a second time in A. dux," says O'Shea.
From issue 2510 of New Scientist magazine, 29 July 2005, page
|Taipan||Jan 11 2012, 01:47 PM Post #5|
Predators - Short-finned Pilot Whales
There is also tantalising, indirect evidence that the whales may sometimes chase down giant squid.
During the dives, the acoustic tags revealed that the whales switched from slower echolocation clicks to a fast series of clicks, or buzz.
That allows them to "see with sound" with greater resolution in the darkness, says co-author Peter Madsen of Aarhus University.
"The analogy is like going from snap-shots to video," he says, indicating the whales are trying to capture prey after the sprints.
But "the prey must be large or calorific to reward the deep dives, and they must be able to move rapidly given the top speeds we clocked for the whales," says Aguilar Soto.
One animal fits the bill, the giant squid Architeuthis. "We found a piece of fresh Architeuthis arm floating in the vicinity of diving pilot whales and findings of bitten Architeuthis are common in the area where the whales live," Aguilar Soto explains.
Also, colleague Pablo Aspas recently took a photo of a pilot whale half-breaching with a piece of large squid in its mouth
"Its colour and the shape of the cups indicate it may well belong to Architeuthis and the size of the piece indicates that the full length of the tentacle would be more than two metres, corresponding to a squid 4-5 metres long and some 180kg in weight," says cephalopod expert Angel Guerra of the Institute for Marine Investigations in Vigo, Spain.
"We have imagined battles between sperm whale and giant squid. But it may turn out that it is pilot whales, one-third the size of sperm whales, which are sprinting for the giant squid!" says Aguilar Soto.
|Taipan||Jan 11 2012, 01:47 PM Post #6|
Giant squid netted in Victoria
Posted Mon May 26, 2008 5:27pm AEST
Updated Mon May 26, 2008 5:55pm AEST
The squid weighs 230 kilograms and is six metres long (Fisheries Victoria)
Map: Portland 3305
A giant squid has been found off Portland in Victoria's south-west.
The six-metre long, 230-kilogram squid was still alive when it was netted by commercial fishermen last night.
Fisheries Victoria says the creature is being kept in a freezer and will be transferred to the Melbourne Museum.
The museum is yet to confirm whether it will be used for scientific research or put on display.
Bob McPherson of the local sport and Game Fishing Club says it is not the first squid netted off Portland, but it is the largest.
The giant squid found off the coast of Portland (Fisheries Victoria)
|Taipan||Jan 11 2012, 01:47 PM Post #7|
Museum to display giant squid
Posted 10 hours 21 minutes ago
Updated 10 hours 10 minutes ago
A giant squid caught near Portland in western Victoria on Sunday night will be used for research and then put on display.
Museum Victoria staff examined it yesterday.
The squid will be taken from Portland to Melbourne later this week.
Museum Victoria's Mark Norman says it is exciting to be able to preserve a creature that is six metres long and weighs 230 kilograms.
"What's been exceptional is that it's come up in a trawler net, very gently from, 550 metres deep and the crew of the Zeehaan were fantastic at making sure it was covered in ice and kept in really good condition," he said.
"And the fact that the ice is still on the animal means we probably can find out more about the little know mating behaviour of these animals."
|Taipan||Jan 11 2012, 01:48 PM Post #8|
Scientists probe giant squid sex secrets
Posted Tue Jun 3, 2008 11:27am AEST
Updated Tue Jun 3, 2008 12:38pm AEST
Victorian scientists are preparing to dissect a giant squid caught off the state's south-west coast last week, hoping to find out more about the enigmatic marine creature.
Early this morning staff from Museum Victoria collected a huge block of ice containing the creature, which is Australia's largest discovered giant squid.
The animal has three hearts and blue blood, boasts a donut-shaped brain that surrounds its oesophagus, is six metres long, and weighs 240 kilograms.
Dr Mark Norman, the senior curator of molluscs with Museum Victoria, says the latest discovery provides him and fellow scientists with a unique opportunity.
"This giant squid is really interesting. It is the biggest we have seen in Australia and it is a little bit bigger than some we've seen [worldwide]," he said.
"But the exceptional thing about it is that it is in very good condition in that the eyes are still intact, all the skin is still on it, the fin is still attached."
He says because its food must be swallowed through the ring-shaped brain, the head and mouth has had to adapt.
"They've got this giant beak like a giant parrot with a tongue covered in teeth, and they have to puree the food so they don't get a splitting headache every time they swallow."
While giant squids periodically wash up on beaches around the world and scientists have studied them in fits and bursts, Dr Norman says there are still huge gaps in knowledge.
Next on the agenda for the frozen body is intensive research.
"Our aim is that we will do a proper autopsy and dissection," he said.
He says the reproductive habits of giant squids are particularly interesting and will be the focus of much study.
"[We will look at] whether it has been mated or not. Whether it is a male or female.
"Giants have very strange sexual behaviour where the male has a metre-long muscular penis that he uses a bit like a nail gun and shoots cords of sperm under the skin of the female's arms and she carries the sperm around with her until she is ready to lay her big jelly mass of a million eggs.
"[We want to find out] whether they gather somewhere together to mass-breed.
"If we get some sperm out of the arms of this animal then we can do paternity studies and see if was multiple males that are mating with her or single males.
"It is very, very strange for the systems going on down there, but because these animals are probably few and far between, we don't know how often they get together to mate."
With the animal in such good condition, the museum has been presented with a rare opportunity to glean knowledge on one of the world's most intriguing creatures.
But the general public will not be forgotten, and the giant mollusc is destined to be a museum piece eventually.
"Once we have done all the times and things we are going to do the 'Frankenstein' job and stitch it all back together and then put it on display at the museum." he said.
|Taipan||Jan 11 2012, 01:48 PM Post #9|
Cannibal squid dissected live on internet
Posted 1 hour 29 minutes ago
Scientists in at the Melbourne Museum have completed a public dissection on a giant squid caught off the coast of Victoria earlier this year.
The giant squid weighs 245 kilograms and in its natural environment would have reached 12 metres in length.
Its large, white body was examined in front of a large crowd at the museum and was shown live on the internet.
Scientists explained that the deep sea creature is a ancestor of the common snail.
They say it is colour blind and has cannibalistic tendencies, with the female often eating the male of the species. They say it is a female squid.
The male of the species has a penis which is approximately 1.5 metres in length and operates like a nail gun, shooting sperm into the arm of the female.
The scientists have taken DNA samples from the skin to try and work out more about the sexual practises of this little understood animal.
Scientists took apart the beak, which is used to rip apart the flesh of its prey.
It is just 30 kilos lighter than the the largest ever giant squid found to date.
The body fills up the pockets of ammonia to help keep the squid afloat.
Sperm whales are the natural enemy of the giant squid. They take six or seven breaths and dive down up to six kilometres under water to find the squid and kill them.
The giant squid weighed 245 kilograms.
|Taipan||Jan 11 2012, 01:49 PM Post #10|
Giant Squid Caught Alive, Briefly, off U.S.
September 22, 2009—For the first time, a live giant squid—shown on the deck of a research ship on July 30—has been caught in the Gulf of Mexico, U.S. officials say. The deep-dwelling squid, however, died during the trip to the surface.
On July 30, during routine test runs for an upcoming whale study, the team dipped their giant net more than a third of a mile (a half kilometer) down and came up with something "really crazy," said Anthony Martinez, a marine mammal scientist with the U.S. National Oceanographic and Atmospheric Administration (NOAA) Fisheries Service.
Measuring about 19.5 feet (6 meters) long and 103 pounds (47 kilograms), the likely juvenile giant squid was alive when netted but didn't survive the ascent to the surface.
The squid's length indicates that it's probably a female and probably was immature, said Michael Vecchione, a squid expert at the Smithsonian Institution.
Adult giant squid are believed to reach about 60 feet (18 meters) in length. Along with their cousins, the colossal squid, giant squid have the largest eyes in the animal kingdom, measuring some 10 inches (25 centimeters) in diameter. These massive organs allow giant squid to detect objects in the lightless depths where most other animals would see nothing.
Like other squid species, they have eight arms and two longer feeding tentacles that help them bring food to their beaklike mouths. Their diet likely consists of fish, shrimp, and other squid, and some suggest giant squid might even attack and eat small whales.
Giant Squid Battle Sperm Whales in the Gulf?
Most captured giant squid—about one or two a year, all of them dead on arrival—are pulled up off Spain and New Zealand, where deep-water fishing is common, Vecchione said.
The new giant squid discovery adds to evidence that a rich and in some cases bizarre variety of squid—including an alien-like squid with "elbows" recently found at an oil-and-gas drilling site—inhabits the Gulf of Mexico.
The newfound giant squid's main scientific significance is as confirmation that sperm whales found in the northern Gulf—often surprisingly near the heavily traveled shipping lanes at the mouth of the Mississippi River—have a local source of their main food.
Bits of giant squid had already been found in the stomachs of sperm whales and other predators from the Gulf of Mexico and nearby waters.
"Finding this specimen in the Gulf of Mexico in the area they were studying confirms the idea [of sperm whales] hanging around there because there's good food," Vecchione said.
Giant Squid Surprise
The research trawls that caught the giant squid about 130 miles (209 kilometers) off the Louisiana coast were a side project for a 60-day marine mammal survey by NOAA scientists, said NOAA's Martinez, who was chief scientist on expedition.
"We knew there was a possibility of catching a giant squid. But it was not something we were banking on," he said.
"We weren't planning on many trawls in the first place. We were really approaching it as a learning opportunity and didn't think we'd score anything really crazy while learning."
As a result, the crew "didn't have anything prepared ahead of time for storage of such a large specimen," Martinez said.
The team lined a big basket with garbage bags. The squid went into the innermost bag, and the whole thing went into the freezer.
Thanks to the MacGyver-esque maneuver, the giant squid may soon spill its secrets. Its DNA can be compared to that of other giant squid around the world, for one thing.
For another thing, the giant squid's little-known menu may become clearer, the Smithsonian's Vecchione said. "If we get a chance to open up the stomach and see what's in it, that can add a lot to" the limited knowledge of giant squid diet.
|Taipan||Mar 16 2012, 02:10 PM Post #11|
Giant squid eyes are sperm whale defence
Richard Black By Richard Black Environment correspondent, BBC News
15 March 2012 Last updated at 17:21 GMT
Artwork of battle between colossal squid and sperm whale Sperm whales are believed to do battle with colossal squid, though such a fight has not been observed
The world's biggest squid species have developed huge eyes to give early warning of approaching sperm whales.
Colossal and giant squid both have eyes that can measure 27cm (11in) across - much bigger than any fish.
Scientists found that huge eyes offer no advantages in the murky ocean depths other than making it easier to spot enormous shapes - such as sperm whales.
Writing in Current Biology journal, they say this could explain the equally huge eyes of fossil ichthyosaurs.
Lead scientist Dan Nilsson from Lund University in Sweden was present at the unique dissection of a colossal squid performed four years ago in New Zealand.
There, he examined and handled the eyes - in particular, the hard parts of the lens.
These alone are bigger than an entire human eye.
"We were puzzled initially, because there were no other eyes in the same size range - you can find everything up to the size of an orange, which are in large swordfish," Prof Nilsson told BBC News.
"So you find every small size, then there's a huge gap, then there are these two species where the eye is three times as big - even though squid are not the largest animals."
The streamlined giant squid (various species of Architeuthis) and the much chunkier colossal squid (Mesonychoteuthis hamiltoni) can both grow to more than 10m long, as measured from the tip of the body to the end of their tentacles.
The colossal squid especially is equipped with a fearsome arsenal of weapons, including barbed swivelling hooks.
Prof Nilsson with core of squid eye lens Dan Nilsson saw the colossal squid's eyes during the dissection in New Zealand in 2008
Scars on the bodies of sperm whales indicate that the two creatures regularly do battle, while colossal squid beaks found in the stomachs of sperm whales indicate that the latter often win.
Though colossal squid are encountered remarkably rarely by people, they are thought to make up about three-quarters of sperm whales' diet in the Southern Ocean.
Whereas the whales can spot squid using sonar, the squid can deploy nothing except vision - which suggests there would be a powerful evolutionary pressure towards developing effective eyes.
Prof Nilsson's team used mathematical models of how different sizes of eye perform at depths up to 1km.
There, moving objects are most detectable through the bioluminescence they provoke from countless tiny creatures in the water.
Squid length graphic
The models showed that in general, there is no benefit to be gained from developing eyes bigger than the swordfish's.
The exception is a really large moving object.
Here, large eyes enable better detection of a pattern of point sources of bioluminescence - light given off by tiny organisms - in low-contrast conditions.
This would give the squid warning of a sperm whale approaching at a distance of about 120m, the researchers calculate - potentially allowing it to take evasive action and avoid being eaten.
"It's the predation by large, toothed whales that has driven the evolution of gigantism in the eyes of these squid," commented Soenke Johnsen, a biologist at Duke University in Durham, US, who was also part of the research team.
They speculate that eyes of the same size might have enabled ichthyosaurs, large marine reptiles that died out about 90m years ago, to avoid the fearsome jaws of the even larger pliosaurs.
|Taipan||Jan 10 2013, 02:08 PM Post #12|
Mysterious Giant Squid Finally Caught on Film
by LiveScience Staff
Date: 08 January 2013 Time: 01:00 PM ET
This image of the long sought-after giant squid is part of a Discovery Channel documentary on the largest deep sea creatures.
The notoriously elusive giant squid has been filmed for possibly the first time in its natural habitat after a Moby Dick-style hunt for the deep-sea beast.
A Japanese-led team filmed the silvery cephalopod last year off the Ogasawara Islands, about 620 miles (1,000 kilometers) south of Tokyo, according to news reports. The footage is to be broadcast in the United States this month.
"It was shining and so beautiful," team leader Tsunemi Kubodera, a zoologist at Japan's National Museum of Nature and Science, told AFP. "I was so thrilled when I saw it first hand, but I was confident we would because we rigorously researched the areas we might find it, based on past data."
Kubodera and his colleagues also captured the first live videos of the deep-sea eight-armed squid (Taningia danae) in its natural environment, finding the biolumescent beast to be a fast, aggressive predator. The squid's light flashes may serve to blind prey or even woo mates, the team found.
In the new achievement, Kubodera, along with a team from Japanese public broadcaster NHK and the Discovery Channel, used a submersible vessel in their search for the legendary creature. After about 100 descents, the three-man crew finally spotted a 10-foot (3-meter) giant squid (formally called Architeuthis) at a depth of around 2,066 feet (630 meters) and followed it down to 2,950 feet (900 m) as it swam with a bait squid in its arms, according to AFP.
The 10-foot (3-meter) squid was filmed off the coast of Japan.
"Researchers around the world have tried to film giant squid in their natural habitats, but all attempts were in vain before," Kubodera told the news agency. "With this footage we hope to discover more about the life of the species."
The giant squid has razor-toothed suckers and basketball-sized eyes and it's believed to be able to grow to more than 32 feet (10 meters) in length. The enormous and elusive creature has been steeped in mystery and legend, possibly inspiring the Norse legend of the sea monster the Kraken and even the Scylla from Greek mythology.
|Taipan||Mar 20 2013, 04:58 PM Post #13|
Squid genes crack secrets of the 'Kraken'
Wednesday, 20 March 2013 Genelle Weule
One of the samples analysed came from a tentacle of a giant squid filmed by Japanese scientists earlier this year
The giant squid has inspired legends about sea monsters, now a new genetic analysis reveals some of the enigmatic creature's secrets.
Although the giant squid Architeuthis is the second-largest invertebrate in our oceans, remarkably little is known about the animal that inspired the legend of the ship-devouring Kraken and the fiction of Jules Verne and Herman Melville.
Growing up to 18 metres in length, giant squid live in all the world's oceans except in polar regions.
Most of what is known about this elusive animal has been gleaned from remains that have been found in the stomachs of whales, washed ashore or caught in fishing nets. It has only recently been glimpsed alive in its natural habitat.
To delve into the secret life of the giant squid, an international team of researchers led by Thomas Gilbert and masters student Inger Winkelmann from the Centre for GeoGenetics at the University of Copenhagen has analysed the mitochondrial DNA of 43 specimens collected from around the world.
The samples included a five-metre tentacle from a squid that was captured on film earlier this year swimming off the coast of Japan.
The team's findings, reported in today's Proceedings of the Royal Society B show all the specimens belong to just one species - Architeuthis dux.
Cephalopod expert and Museum Victoria head of science Dr Mark Norman says the findings are very exciting.
"We're all blown away talking about a common species worldwide," says Norman who collected some of the tissue samples for the study.
"For quite a while we suspected there were three species of giant squid because their body shapes seemed a bit different between North Pacific, right round Antarctica and then in the Atlantic Ocean.
"The deep sea is the most common habitat on Earth and this genetic study shows it's all connected."
Ocean highways and bottlenecks
The researchers suspect part of the squid's low diversity may be due to the animal's lifecycle.
After they hatch, juvenile squid are carried along with plankton by shallow currents, then they move deeper as they age, says Norman.
"They are all swimming on highways between those huge ocean masses," he says.
"Either as juvenile stages or free swimming adults they're covering an enormous geographic range within the one species. So maybe it's like an albatross that covers the world in its lifetime."
Another factor that may have contributed to low diversity is revealed by a comparison of the squid's DNA markers to the fossil record of other molluscs, says another co-author Dr Jan Strugnell from La Trobe Institute for Molecular Science.
"There are no known fossils of giant squids," says Strugnell, who helped with the molecular analysis. "The way that fossils come into this study is to enable us to see when dates have occurred in the past."
Strugnell says the analysis shows the squid population went through a bottleneck followed by a rapid expansion between about 32,000 and 115,000 years ago, which coincides with the last ice age.
"If you compare the genetic diversity of this [squid] species with lots of other species, the genetic diversity is extraordinarily small," she says.
"We can't be sure, but [the ice age] may have changed the abundance of some predators that were competing with the squid.
"So the population has increased in size, but the genetic diversity perhaps hasn't recovered from that time."
|coherentsheaf||May 6 2013, 10:58 AM Post #14|
The original paper has been called into question: http://www.biomedcentral.com/content/pdf/1471-2148-13-45.pdf
|Taipan||Oct 5 2013, 02:41 PM Post #15|
Elusive Giant Squid Washes Up on Spanish Beach
By Jeanna Bryner, Managing Editor | October 04, 2013 09:05am ET
This giant squid called Architeuthis dux and measuring 30 feet long washed ashore in the Spanish community of Cantabria on Oct. 1, 2013.
A giant squid, whose oversized eyes and gargantuan blob of a body make it look more mythical than real beast, washed ashore Tuesday (Oct. 1) at La Arena beach in the Spanish community of Cantabria.
The beast measures some 30 feet (9 meters) in length and weighs a whopping 400 pounds (180 kilograms); and according to news reports, it is a specimen of Architeuthis dux, the largest invertebrate (animals without backbones) on Earth.
The giant squid is currently at the Maritime Museum of Cantabria, according to El Diario Montanes.
Perhaps fortuitously, an underwater photographer happened to be in the area at precisely the time the squid washed ashore. "I felt privileged to be among a few, these animals rarely can be seen, because they live at great depths and very few appear on the coast dead," Enrique Talledo told LiveScience in an email. "Its appearance is similar to a sea monster, well-adapted to life in the depths."
Tsunemi Kubodera, a zoologist at Japan's National Science Museum in Tokyo, and his colleagues, captured the first live footage of an Architeuthis giant squid in its natural habitat in 2012. The video revealed the elusive creature off the Ogasawara Islands, about 620 miles (1,000 kilometers) south of Tokyo at a depth of around 2,066 feet (630 m); the three-man crew aboard a submersible followed the giant squid down to 2,950 feet (900 m).
This giant squid called Architeuthis dux and measuring 30 feet long washed ashore in the Spanish community of Cantabria on Oct. 1, 2013.
"It was shining and so beautiful," team leader Tsunemi Kubodera, a zoologist at Japan's National Museum of Nature and Science, told AFP at the time. "I was so thrilled when I saw it first hand, but I was confident we would because we rigorously researched the areas we might find it, based on past data."
In addition to boasting record-large size, the giant squid also sport the animal kingdom's largest eyes, which can be as big as a human head, according to the University of Michigan's Museum of Zoology. These enormous peepers likely allow the squid to see in the deep-sea where minimal light is available. Though little is known about where these squid live, scientists say the giants likely reside in cooler waters, as research has shown their blood doesn't carry oxygen well at high temperatures.
Like other cephalopods, a group that includes squid, octopuses, cuttlefish and their relatives, Architeuthis is thought to have an extensive nervous system and complex brain.
Steeped in mystery and legend, the deep-sea giant is said possibly to have inspired the Norse legend of the sea monster the Kraken and even Greek mythology's Scylla, a sea monster said to live in a narrow channel of water opposite its monster counterpart Charybdis.
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