Sea sponge size of a minivan could be one of world's oldest living animals

Christopher Kelly says the researchers called their find 'the folded blanket sponge' because 'it looks as though somebody took a blanket and draped it over a chair'. Photo / NOAA

The deep sea is dark and full of mysteries.

Way below the water's surface north of the Hawaiian islands, a remotely operated vehicle (ROV) has spotted a massive creature hitherto unknown to science.

The ROV captured footage of the spectacularly large sponge during a National Oceanic and Atmospheric Administration (NOAA) deep-sea expedition, and the species was identified for the first time in a study published yesterday in the journal Marine Biodiversity.

According to NOAA, the "sponge the size of a minivan, the largest on record", measured 3.6m by 2.1m.

Prior to this discovery, the largest recorded sponge was one discovered in shallow waters off western Canada in the late 1800s. It measured about 3.3m long and 1m wide.

And there's more to this sponge than its girth: It could also be among the oldest living animals on earth. (Yes, here is your obligatory reminder that, while sponges may look like weird underwater plants, they belong to the animal kingdom.)

Sponges can live for hundreds or even thousands of years.

"While not much is known about the lifespan of sponges, some massive species found in shallow waters are estimated to live for more than 2300 years," the study authors write.

The sponge was discovered last summer in the Papahanaumokuakea Marine National Monument, a 362,600sq km marine conservation area.

"Finding such an enormous and presumably old sponge emphasises how much can be learned from studying deep and pristine environments such as those found in the remote Papahanaumokuakea Marine National Monument," Daniel Wagner, Papahanaumokuakea research specialist, said in a statement.

Wagner told New Scientist that he estimates the sponge to be around 1000 years old.

"Sponges don't have things like growth rings that can be used to estimate age," Wagner said. "We do know, however, that several coral species that live at those depths can live to multiple hundred to even a few thousand years: the oldest one is 4500 years."

Christopher Kelly, NOAA research scientist and co-lead for the expedition, said the sponge "just appeared" on the ROV's high-definition camera, Australia's Pacific Beat radio reported. "We were looking for deep-water corals and sponges, and we had just gotten some close-ups of some corals, then turned away to continue the survey and the sponge appeared out of nowhere," he told the outlet.

And "it looked like a folded blanket", he added. "It looks as though somebody took a blanket and draped it over a chair ... so that's what we called it until we got a better name for it, the folded blanket sponge."

That this deep-ocean sponge doesn't appear to have been disturbed may have allowed it to become so large. "A lot of organisms in deep seas grow very slowly, so they need their habitats to remain stable over a long time to be able to grow larger and larger," Wagner said.

This particular organism wasn't sampled. But a sample was collected nearby during a previous expedition of what researchers believe to be the same species, belonging to the Rossellidae family of sponges.