HANDOUT - Schwämme Credit: Dr. B. Müller - University of Amsterdam ACHTUNG: Frei nur zur redaktionellen Verwendung im Zusammenhang mit der Berichterstattung über die Studie bei Nennung des Credits. Foto: Dr. B. Müller - University of Amsterdam

Sponges are among the oldest multicellular organisms on earth and play an important role in the food cycle of many marine ecosystems.

Sneezing out mucus is probably one of the oldest ways for organisms to rid themselves of unwanted debris. However, this mechanism has remained largely unexplored in sponges. The animals were thought to passively flush out waste products with the flow of water through the main body opening, called the osculum.

However, some studies have observed that when sponges are exposed to heavy debris, they contract their bodies and secrete mucus to remove sediment from their bodies and protect their duct system from clogging. The mucus was not secreted through the osculum, but through smaller pores in the top layer of the sponges, the ostia. However, the exact mechanism behind this phenomenon was previously unclear.

But how do the sponges manage to transport the slime against the inflowing water flow? In other animal species, small eyelash-like structures, the cilia, usually ensure that the mucus flows in the right direction. However, the cilia of the stovepipe sponge appear to be largely immobile.

Without muscles and nerve cells, a sponge also sneezes much more slowly than, say, a human: unlike us, it takes about half an hour to sneeze. It is therefore reasonable to assume that the scientists have discovered a new type of sneezing mechanism. The periodic contraction and relaxation of the sponge, followed by a sneeze, could represent an early step in the evolution of muscle cells, they suspect.

Sneezing doesn’t just help the sponge keep itself clean. Video recordings by the research team also show that secreted clumps of mucus and the waste products they contain are a source of food for various sea creatures such as fish or worms.

The team’s results not only shed light on the metabolism of one of the oldest animal families, but also suggest that sponges most likely play an even greater role in the underwater food cycle than previously thought.