The Largest Known Sponge Is the Size of a Minivan, and Its Species Is Unknown

The largest sponge ever measured sits on a ridge deep in the Pacific Ocean near Hawaiʻi, roughly the size of a minivan, and more than a decade after it was found nobody can say what species it is.

A minivan-sized animal, 7,000 feet down

In 2015, scientists aboard the NOAA Ship Okeanos Explorer were exploring the Papahānaumokuākea Marine National Monument, a protected stretch of ocean in the Pacific. Two remotely operated vehicles, named Deep Discoverer and Seirios, were working 2,130 meters (about 7,000 feet) below the surface when they came across the animal on a ridge.

It measured nearly 3.7 meters (12 feet) long, 2.1 meters (7 feet) wide and 1.5 meters (5 feet) tall. NOAA's own description of it is the one everyone repeats: about the size of a minivan.

Getting those numbers took some care. Two parallel laser beams were projected onto the sponge so the team could measure its height and width. Pictures taken from above by the second vehicle helped them work out its length.

Bigger than the old record, but still nameless

The previous record-holder was a glass sponge called Aphrocallistes vastus, found in shallower water off western Canada. It measured 3.4 meters long, 0.5 meters wide and 1.1 meters high — long, but narrow and low next to the new find.

The researchers did not take a piece of the giant itself. Instead, they collected a smaller sponge from a nearby spot that they believed belonged to the same species. Under the microscope, its tiny skeletal parts, called spicules, showed that it belonged to a family of glass sponges called Rossellidae. The exact species has never been identified.

That makes the find even stranger. The expedition carried out 18 dives, and only two sponges that appeared to be this species were ever seen.

Glass sponges are named for their delicate skeletons, which are made of silica — the same material as glass. Like other sponges, they are animals that pull seawater through their bodies to filter out tiny pieces of food. Their bodies also give shelter to other sea creatures, so a sponge this big can shape the life around it.

The age question has no answer either

How long does it take to grow something the size of a minivan? For this sponge, nobody knows. But other large sponges are thought to live for extraordinary lengths of time. A 2008 study of giant barrel sponges suggested that some individuals could be more than 2,300 years old.

Whether the deep-sea sponge is anywhere near that old is unknown. The researchers' account of the discovery was published in the journal Marine Biodiversity in 2016, and its species and age are still open questions.

NOAA marine biologist Daniel Wagner said in 2016 that "the largest portion of our planet lies in deep waters, the vast majority of which has never been explored." He added that finding such an enormous and presumably old sponge shows how much can be learned from deep, untouched environments like the monument where it was found.

Because most of the seafloor has never been looked at with cameras or vehicles, there may be a bigger one out there still.