Squid that feel lingering pain act with higher vigilance around predators.
What has eight arms with hundreds of suckers, eyes the size of grapefruit and a razor-sharp beak? A giant squid! A team of scientists and the Discovery Channel shot footage of this notoriously elusive creature in action. Click ahead for more squidly fun.
Giant squid have captured, and terrified, the seafaring imagination for centuries. This illustration recreates a giant squid observed off Tenerife in November of 1861.
This giant squid was collected by NOAA researchers off the Louisiana coast in the Gulf of Mexico. The largest invertebrate on Earth, the giant squid is just plain big -- the largest ever found was 59 feet (18 meters) long.
The only squid bigger than a giant is the colossal squid. Captain John Bennett examines the world's first intact adult male colossal squid in 2007 in the Ross Sea, near Antarctica. The squid was about 33 feet (10 meters) long. Check out those suckers!
These two female giant squid were found off Luarca, Spain. For an idea of the size of these creatures, note the gloved hand in the upper-left.
Alien autopsy? Nope. It's one of the Luarca squid from the previous slide, undergoing an examination by Spanish scientists.
Here's a giant squid measuring about 28 feet (9 meters), on display at London's Natural History Museum. This creature was caught in March of 2004, at a depth of 722 feet (220 meters), off the Falkland Islands in the South Atlantic.
A cat strolls past a giant squid in January 2005 in Newport Beach, Calif. That winter hundreds of 3- to 4-foot-long (0.9 to 1.2 meter) squid washed up along the Southern California coast. One theory holds that they ran ashore while chasing grunion.
This is another shot of a squid from the Newport Beach, Calif. wash-up. Giant squid eyes look so human because they’re structured much like human eyes are.
It may look big in the photo, but this larval squid is just 0.4 inches (1 centimeter) long and was photographed through a microscope by Russ Hopcroft, of the University of Alaska Fairbanks.
The humboldt, or jumbo, squid is a carnivorous marine invertebrate with a lifespan of only 1-2 years. But it makes hay while the sun shines on its short life: In that time, it can grow to 4 feet (1.2 meters) long.
We may know it better as calamari, the familiar appetizer, but its proper name is common market squid. This adult market squid was photographed off La Jolla Shores Beach in La Jolla, Calif.
This adult jumbo squid was caught near the Channel Islands by a squid jig aboard an NOAA research ship in 2007. Its tentacles are wrapped around the jig that was used to catch it, which worked by attracting the squid to its glowing yellow plastic.
This is a closer look at the 2007 Channel Islands squid. Its telltale large eyes allow the creature to see in the very low light that permeates its deep underwater habitat.
A squid's razor-sharp beak is a merciless weapon against its prey, allowing it to chomp tasty bites out of its victims. Here we see a close-up of a Caribbean reef squid's beak.
Lasting feelings of pain or anxiety after an injury may seem perplexing, but they serve an evolutionary purpose, research suggests.
Squid that behave more vigilantly after even a minor injury are more likely to survive than their more brazen counterparts, a new study reveals. The findings suggest that persistent pain may be more useful than once thought, according to the study published today (May 8) in the journal Current Biology.
This study provides the first direct evidence to suggest that animals developed heightened sensitivity— which promotes pain in some animals — in response to natural selection, particularly to avoid predators, said study researcher Edgar Walters, a biologist at the University of Texas Medical School at Houston. [5 Surprising Facts About Pain]
No pain, no gain
To study the evolution of lasting pain, Walters and his team studied how squid interact with their predators, black sea bass.
When squid feel threatened, they perform a step-by-step series of defensive behaviors, even if the predator is far away, the researchers said. The scientists observed squid and black sea bass swimming in laboratory tanks, and compared how healthy and injured squid responded to different levels of perceived danger.
The squid could still get around with an injury to one of their arms, but this put them at a disadvantage because the bass would preferentially hunt the injured animals, and from further distances, too. When bass were hunting injured squid, the prey became more vigilant, acting more defensively than their uninjured slimy brethren.
Next, the researchers treated squid with an anesthetic that prevented them from feeling pain when injured, and the animals failed to display defensive behavior that would have kept them alive.
The sensation of pain that made the squid hyper-vigilant could be analogous to the same feelings in humans, the researchers said — although the squid may feel something completely different from human pain. Still, the squids' response to injury offers a new perspective for understanding human responses to pain.
If scientists can understand more about the natural purpose of pain sensitivity, they might be able to find ways to treat pathological pain in humans, the researchers said.
Original article on Live Science.
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