May 5, 2008 -- Scientists examining the world's largest known colossal squid this week could find nothing in the cephalopod's stomach, suggesting the large marine animal was starving when it was captured in February of 2007.
That might help to explain why the squid was caught in the first place. The huge, jelly-like animal from Antarctica was voraciously eating an Antarctic toothfish hooked in a New Zealand long-line fishing operation in the Ross Sea when fishermen hauled up their catch, revealing the then half-dead, enormous squid.
View a slideshow of the colossal squid here.
The fishermen netted the squid and placed it in their vessel's freezer. It remained frozen until last week, when scientists at The Museum of New Zealand Te Papa thawed and analyzed the squid. Part of that investigation involved the insertion of an endoscope into the specimen's stomach.
"The endoscope revealed nothing," museum spokesperson Jane Keig told Discovery News. "Its stomach was empty."
Last week, the squid project's director, Carol Diebel, told Discovery News there were plans to remove tissue samples from the squid's stomach, but the researchers instead decided not to cut into the colossal squid, as "any kind of dissection could harm it" before the squid goes on public display in a specially constructed fluid-filled tank.
The Colossal Squid's Favorite Food
Diebel and her team instead focused their dissection efforts on yet another colossal squid housed in the museum. This second squid was laid out on a trough-like table next to the primary specimen for much of the week.
The stomach of that second squid yielded the remains of toothfish. Prior studies of colossal squid remains found in the stomachs of whales also revealed evidence of toothfish consumption, so scientists believe this fish could comprise a large portion of the colossal squid's diet.
The word "toothfish" generally refers to two closely related species: the Patagonian toothfish, popularly known as Chilean sea bass, and Antarctic cod, which is sometimes referred to as Antarctic toothfish. Both species possess a rather toothy, gaped mouth, hence the name, and can grow to around 7 feet or more in length.
Recently it was determined that the Antarctic toothfish possesses special proteins in its body that act like anti-freeze, preventing its blood from freezing into a solid block in the ice-laden, high latitude waters where it lives. Both the toothfish and the colossal squid favor deep water, 3,000 or more feet below the surface, and each has developed special adaptations to live and hunt in the darkness of that environment.
Hunting in the Dark
During this week's colossal squid investigation, the researchers were able to get an up-close look at the squid's tentacles. The tentacle tips -- appropriately called "clubs" -- are armed with two rows of sharp hooks that can swivel in all directions.
While no one has closely observed a colossal squid in hunting action, it's believed the animal moves quickly, grabbing toothfish and other prey with these spiked tentacles, which ironically somewhat resemble long-line fishing lines.
The scientists also discovered the squid has basketball-sized eyes, "the largest known in the animal kingdom," according to Diebel, along with a light organ right near the eye sockets. She believes this organ may function like a searchlight.
Toothfish also possess special eyes, with retinas that are well adapted to low light levels. While the mostly clear squid is nearly invisible in deep water, it's probable that colossal squid and toothfish play a continual hide and seek game of survival, where who spots whom first determines which one could live another day.
The Big Beak's Bite
The defrosted colossal squid's beak suggests the animal was much larger than it is now, a fact that's been supported by the men who witnessed the squid before it went into the freezer. Due to water and temperature changes, the squid shrunk to around 14 feet in length. Despite such alteration of the squid's flesh, its beak remains fully intact.
Among the colossal squid's many mysteries has been: How can an animal the consistency of firm Jell-O bite into prey without tearing itself to pieces?
Another team of scientists at the University of California, Santa Barbara grappled with that issue just a few weeks ago and discovered that squid beaks possess various gradations of stiffness, depending on the amount of a certain type of protein. The protein-filled beak tip is quite stiff and hard, with little water around its molecules, while the area around the base contains more water and less protein. It is therefore more flexible.
"Here you have a cutting tool that's extremely hard and stiff at its tip and is attached to a material -- the muscular buccal mass -- that has the consistency of Jell-O," said co-author Frank Zok.
"You can imagine the problems you'd encounter if you attached a knife blade to a block of Jell-O and tried to use that blade for cutting," he added. "The blade would cut through the Jell-O at least as much as the targeted object. In the case of the squid beak, nature takes care of the problem by changing the beak composition progressively, rather than abruptly, so that its tip can pierce prey without harming the squid in the process.
"It's a truly fascinating design!"
Plans are already in the works to apply the findings to human hip replacements and other medical applications.
Giants Under Human Pressure
Although a colossal squid is thought to be able to sever nerve cords of other animals with a single bite, paralyzing them for later consumption, such skills are little match for the overwhelming pressures brought forth by human activities. Even its recent capture proves that people are encroaching more into its habitat.
No one knows exactly how many colossal squid exist now, but their suspected main predator, sperm whales, are listed as being "vulnerable" on the latest World Conservation Union's IUCN Red List of Threatened Species.
While the New Zealand fishermen who captured the squid were legally approved to fish for Antarctic toothfish in the Ross Sea, the illegal capture and sale of Patagonian toothfish has led to numerous arrests and fines over the years.
Toothfish are very slow-growing. Patagonian toothfish, a.k.a. Chilean sea bass, only reach maturity when they are between 10 and 12 years of age, so recovery from overfishing is difficult to near-impossible. Long-line fishery operations also result in by-catch, killing multiple other species, such as seabirds, whales and other types of squid.
According to the Monterey Bay Aquarium's Seafood Watch Program, people can do their part by avoiding purchase and consumption of Chilean sea bass.
"Scientists estimate that more than half of all the Chilean sea bass sold are caught illegally," said Tim Fitzgerald, an Environmental Defense Fund marine scientist who helps to develop the Seafood Watch list.
He added that Environmental Defense has also "issued a health advisory for Chilean sea bass due to high levels of mercury," so avoiding the fish could potentially benefit humans as well as squid.
Related Links:
Jennifer Viegas' blog: Born Animal