A Colossal Squid From Antarctic Waters
The Age
Monday August 13, 2007
Little is known about the world's largest invertebrate animal. Dr Mark Norman examines an extraordinary creature from the deep sea.
IN the era of super science, nothing shows up how little we know of our own planet as finds of massive "sea monsters". The largest single invertebrate animal ever found was captured in February this year by long-line fishermen in Antarctic seas. Known a colossal squid, it weighs 495 kilograms, around twice the weight of the largest squid ever captured.Colossal squid are different from giant squid.They belong in different squid families and look very different. The scientific name of the colossal squid is Mesonychoteuthis hamiltoni. It in the same family as the small transparent glass squids that live in the dark depths of open oceans worldwide (family Cranchiidae). Colossal squid are very impressive animals. The latest discovery is 10 metres long, has eyes larger than blue whale's, a sharp slicing beak as big as a rockmelon and a tongue covered in sharp teeth.eight arms and two thick feeding tentacles are armed with toothed suckers and sharp hooks. It swims with large muscular fins and a big funnel jet propulsion. The undersides of its eyes have rows of lights like truck running lights.In contrast, giant squids are very different animals. There is more than one species and they all belong in the family Architeuthidae. The species found in Australian waters has a scientific name of Architeuthis sanctipauli. They reach more than 15 metres long but are thinner than colossal squid, the heaviest on record being less than 300 kilogram. Two-thirds of the length of a giant squid is a pair of long thin feeding tentacles that can be zipped together to form a single long shaft with a pair of paddle-like pads at the end. Each pad is covered in sharp toothed suckers.The latest discovery was a mature male. In many squid groups, including giant squids, the females are bigger than the males. This means that there are probably even bigger squid swimming around out there.This squid is only the fourth non-juvenile colossal squid ever examined by scientists. This despite this squid species being considered the most abundant Antarctic squid by weight. Their beaks have frequently been found in toothed whale stomachs and juveniles are regularly captured in trawl nets. It is amazing that nothing known of the wild behaviour and biology of this squid, the largest invertebrate animal in the world.In the debate over who is bigger, the colossal squid is by far the heaviest (and scariest) while the giant squids are the longest. Neither spends its time sinking ships and eating sailors. Swimmers don't need to be worried as big colossal squid only occur in freezing Antarctic waters and giant squids only occur in the deep sea, between about 500 and 1500 metres deep.This discovery highlights two points. Firstly, that our knowledge of the most common habitat on our planet - the deep sea - is still in its infancy, and secondly that such scientific discoveries indicate the scale and reach of global fisheries exploitation. There is not a corner of the world's oceans that is not being exploited.Dr Mark Norman is senior currator (Molluscs) at Museum Victoria.
© 2007 The Age