The glowing white eyes of a new species of demon catshark that has been discovered in northern Western Australia could lead to a better understanding of the evolution of sharks, a scientist says.
The demon catshark was discovered off the Kimberley coast, about 300 kilometres west of Broome, after researchers found a collection of its eggs.
The senior curator of the CSIRO's Australian National Fish Collection, Will White, said the creature's distinctive white iris was a rare feature for deepwater sharks.
"Normally, they're always very dark — either dark green or just black eyes," he said.
"It has been found only in one other deepwater shark species — a member of a closely related species from New Caledonia and Papua New Guinea."
Dr White said the characteristic could help to establish links between similar species.
"It must have evolved for some particular reason, not just within one species, but within a group of species," he said.
"It has definitely opened up research questions about a different evolutionary pathway that we hadn't considered within this group."
Eggs crack case
In 2011, researcher Brett Human found an unidentified shark egg while he was volunteering at the WA Museum.
Its strong T-shaped ridges had only been found in one other shark species and was unique among egg-laying sharks in Australia.
Mr Human connected the egg to a collection of similar eggs discovered on a marine expedition off the Rowley Shoals in 1989.
He identified them as belonging to the genus Apristurus, but could not determine the species.
Dr White said it was a long process.
"It's interesting, because we often get an idea that something might be a new species, but it can take a long time for us to resolve and compare with other species," he said.
"We very quickly worked out that those cases don't match any other species that belong to that genus in Australia.
"[It was] frustrating, because we didn't have an actual animal to work with."
After looking at the fish collection's databases, Dr White found a specimen that had been identified as a different species.
But when he examined is closely, he found it was a pregnant female.
Dr White and researchers came across the same ridged egg cases inside the specimen and understood the creature was an entirely separate species.
'Still a lot to come'
Dr White said this species of demon catshark was found in water with a depth of more than 700 metres, where it was laying eggs on some coral.
"We don't see a lot of them because of the depth they occur," he said.
"If you look at that coastline, where it's usually quite steep and drops off quickly, they have a relatively narrow depth distribution.
"They're probably following a habitat in which they lay their eggs on a particular coral species."
Dr White said the discovery helped them link it to an animal on the other side of the country.
“We actually uncovered a similar species off the Gold Coast, which is closely related but a very distinct species," he said.
Dr White expected more discoveries in coming years.
"We just know very little about deepwater fauna in Australia," he said.
"As more deepwater surveys continue, I think we'll uncover more species records — there's still a lot to come."
