The giant squid (Architeuthis dux) may be a cannibal according to analysis of its stomach contents by Bruce Deagle at the University of Tasmania .
Little is known about giant squid - sightings have been few and far between. Early human sightings fostered myths of sea monsters (such as the Kraken) perhaps understably. They are the largest invertebrate at up to 18m (that's the length of a bendy bus), have the largest eye of the animal kingdom (25cm diameter) and weigh nearly a ton. No one really knows what they eat, as their stomach contents are usually pulverised to such a soup that no body parts can be recognised.
The cannibal squid in question was caught by fisherman and Deagle and his team analysed the DNA in the 'amorphous slurry' from the squid's gut. The DNA turned out to be that of A. dux (along with the blue grenadier fish). They also found among the slurry some pieces of giant squid tentacle and possible squid beaks.
They don't know however whether the tentacles belonged to a rival squid or whether they were this squid's own - like us biting our nails when nervous, giant squid have been known to chew off their own tentacles when stressed.
1. Deagle BE, Jarman SN, Pemberton D, Gales NJ: Genetic Screening for Prey in the Gut Contents from a Giant Squid (Architeuthis sp.). J Hered. 2005 96(4):417-23