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Giant Squid May Be Cannibals

By Robyn Grace
The Australian, July 28, 2005

GIANT squid may have more on their menu than ill-fated sailors.

Australian researchers have discovered that the mysterious creatures – enshrined in myth as ferocious beasts that attack hapless mariners – may indulge in cannibalism.

The University of Tasmania team used a novel DNA-based approach to test the stomach contents of a 190kg male specimen caught by fishermen off Tasmania's west coast in 1999. Three tentacles and 12 squid beak fragments were found in the stomach of the giant squid.

While the beaks could not be identified, DNA from stomach juices and tentacle fragments all belonged to the giant squid, or Architeuthis dux. The only other species identified was a fish, the blue grenadier, not previously recorded as Architeuthis prey.

The giant squid is the world's largest invertebrate, believed to grow up to 18m in length and weighing up to 900kg. They have eight arms as thick as fire hoses and large and complex brains. But because none have ever been caught alive, mystery still surrounds the species.

They are believed to live at depths of anything between 200m and 700m, and specimens have been found stranded all over the globe.

Identifying the prey of giant squid has also been difficult, due to the scarcity of samples and their tendency to finely macerate their food. To eat, they shoot out two longer tentacles like a bungee cord before drawing their prey into the mouth, where a parrot-like beak chops the meat into small chunks.

PhD student and research leader Bruce Deagle said the DNA results provided a framework for future studies, particularly diet data collection from the giant squid and other rare species such as beaked whales.

Australian Antarctic Division research scientist Simon Jarmon said while the study could not rule out accidental self-ingestion, the Tasmanian research was probably the first time giant squid cannibalism had been demonstrated "reasonably conclusively".

"People for a long time thought that DNA in dietary samples would be too degraded because of all the digestive processes," he said.

Dr Jarmon said scientists would use the DNA technique on marine animals including whales and penguins, but future research of the giant squid was dependent on getting more samples.

"They're such mysterious creatures. You can't really tell anything about them because no one has ever seen one alive, you've got no idea how many there are or what they might be feeding on," he said.

The giant squid's only known enemy is the sperm whale. Whales have been found with squid in their stomachs, and battle scars believed caused by its suckers.