Deep under the sea lies a creature that sort of looks like a ghostly tulip. The glass rope sponge has a cup-shaped, filter-feeding top and a thin anemone-covered stem tethering it to the ground. One of these sponges happened to sit in front of a Monterey Bay Aquarium Research Institute camera that captured a photo every hour for 30 years.
While reviewing the time-lapse footage from between June 2013 and April 2014, researchers at the MBARI noticed something surprisingly relatable: the sponge seemed to sneeze.
“Basically, there’s an ‘ahh‘ when the sponge expands and the ‘-choo’ when it contracts those canals,” explains invertebrate zoologist Amanda Kahn in a statement. “Everyone was watching sea cucumbers and urchins snuffling around on the seafloor, but I watched the sponge. And then the sponge changed size.”
The new research, published in the journal Deep Sea Research Part II, details the first time the behavior has been recorded in glass sponges. The deep-sea sponges are made from a silicate-based material, like glass or opal, unlike most sea creatures that make their hard shells out of chalky calcium carbonate.
Sponge sneezes were first observed in 2014 by a research group led by Sally Leys, an invertebrate zoologist and sponge specialist at the University of Alberta. Sponges are some of the oldest and simplest animals on Earth; they lack bones, brains and guts. (But that hasn’t stopped one glass sponge from living for about 11,000 years.) Many sponges, including the glass rope sponge, are filter feeders. They rely on the ocean’s currents and long, microscopic hairs called flagella to push nutritious microbes onto them, which they absorb.
But like any filter, sponges can get clogged up with the muck that they don’t eat. In 2014, Leys and her colleagues found that eight species of sponges could use shorter hairs, called cilia, to sense the level of muck, and then expand and contract to shake it off.
“The sneeze is a delightful behavior,” Leys told National Geographic’s Karl Gruber in 2014, “and one that is a great tool for understanding how coordination systems may have arisen during the evolution of early multicellular animals.”
The fastest sponge sneezes lasted hours, but sometimes required weeks to cycle from start to finish. The researchers note in their paper that sponges are rarely imaged for longer than a few days at a time, and shallow-water sponges have been observed more often than the deep-sea sponges captured by the MBARI camera.
And while sponges are often thought of as immobile, the researchers found that they simply live life at a different pace. Seen in time lapse footage, some sponges moved less than a fifth of an inch per year. The usually-tethered glass rope sponges can survive detaching from the ocean floor and rolling several body-lengths away.
“The deep sea is a dynamic place, but it operates on a different timescale and with different stimuli than our world,” says Kahn in the statement. “We don’t know what they’re responding to yet, but we’re going to study that next.”