JOIN USAn international team, led by the University of Western Australia, made the discovery while undertaking an expedition to study mesopelagic fish (midwater fish that live at depths of over 100 metres) and how they use bioluminescence (self generated light) to survive at these depths.
Working with teams of scientists from Britain, the US, Japan, Germany and other parts of Australia, 20 trawls were undertaken at depths ranging from 100 metres to 1,700 metres.
"It is suspected that at least three new fish species may have been discovered but this awaits verification by the experts on board from the Australian and Victorian museums," Professor Shaun Collin, who led the team, said.
He added: "But how do these deep-sea fishes manage to migrate upwards nearly 1000 metres every night to feed in the nutrient rich upper water layers when there is little or no sunlight to signal night and day?
"We're interested in what the function of the pineal is in the deep sea and whether these image-forming eyes also play a role in setting their circadian (daily) rhythms."
As depth increases, the selection pressures to retain image-forming eyes is large and although many species have risen to the challenge and possess large specialised eyes, others appear to have become degenerate or at least so small as to render them inefficient.
The seemingly degenerate eyes may take the form of small, aspheric globes or simply patches of light sensitive tissue over the head.
However, very little is known about the extent of visual loss experienced by these small eyes and patches of photo-receptive tissue and the environmental pressures (or signals) that initiate their loss of visual function.
"This research will potentially identify the barely essential neural elements that a simple visual system needs to operate. It is the first time that such a wide array of different methods has been applied as an integrative approach for the investigation of sensory systems in deep-sea fish," Professor Collin said.