An elusive species of the "living fossil" nautilus has been spotted for the first time in three decades.
Researchers are concerned that sightings of the incredibly rare animal, Allonautilus scrobiculatus, will become even less frequent as human activity continues to threaten the world's oceans, the University of Washington reported.
The nautilus, which is distantly related to cuttlefish and squid, was discovered in the South Pacific. Its distinctive shell has appeared in the fossil record for over 500 million years, but we still know very little about these mysterious creatures.
"Before this, two humans had seen Allonautilus scrobiculatus," said biologist Peter Ward, who spotted the nautilus last month. "My colleague Bruce Saunders from Bryn Mawr College found Allonautilus first, and I saw them a few weeks later."
The first sightings occurred back in 1984, and the researchers collected Allonautilus scrobiculatus specimens for analysis. The studies showed the "gills, jaws, shell shape and male reproductive structures" were different from what was seen in other known nautilus species.
"Some features of the nautilus - like the shell giving it the 'living fossil' label - may not have changed for a long time, but other parts have," Ward said. "[Allonautilus] has this thick, hairy, slimy covering on its shell. When we first saw that, we were astounded."
To spot the Allonautilus, the researchers set up a "bait on a stick" system in which fish and chicken meat were lowered between 500 and 1,300 feet below the surface on a pole; the activity surrounding this bait was filmed for a period of 12 hours each day.
Footage from a site off the coast of Ndrova Island revealed Allonautilus approaching the bait after its over 30 year absence. Soon after, another species of nautilus arrived and fought to also munch on the bait until a larger sunfish appeared at the scene.
"For the next two hours, the sunfish just kept whacking them with its tail," Ward said.
A bait trap was used to capture a few Allonautilus' at a depth of about 600 feet. The scientists determined the animals' age and genders before returning them to their natural habitat.
The studies suggest most nautilus species are isolated from one another because they can only inhabit a very narrow and specific temperature region of the ocean.
"They swim just above the bottom of wherever they are," Ward said. "Just like submarines, they have 'fail depths' where they'll die if they go too deep, and surface waters are so warm that they usually can't go up there. Water about 2,600 feet deep is going to isolate them."
These findings also suggest that since the different species can only survive under specific conditions, once they become extinct in a region it likely means they will be wiped out for good. Illegal fishing for nautilus shells has already devastated a number of populations. In September, the U.S. Fish and Wildlife Service will decide whether or not they should advocate for the nautilus to become a protected species under the Convention on International Trade in Endangered Species of Wildlife Fauna and Flora treaty.
"As it stands now, nautilus mining could cause nautiluses to go extinct," Ward urged.
