Oh. My.

'They are very evil little animals, which is why they are so fascinating to work with,' Dr Johnston said. 'They squirm around these communities [of creatures which live on hard surfaces and cannot move] and attack the barnacles. They squirt digestive juices into them and suck their flesh out.'

At less than two centimetres long the new flatworm has proven extremely hard to study and categorise.

'They're very difficult to describe because if you try and pick them up with anything other than a very fine paintbrush they break in half,' Dr Johnston said.

The new flatworms are all hermaphrodites, meaning they have both male and female parts. To reproduce they try to stab each other with their genitals. The first to penetrate inserts sperm and then goes on to spar with another flatworm, while the 'loser' lays and broods the eggs.

Sydney Morning Herald :: What lurks beneath - flesh-sucking sex fiends