Animal Without a Brain Can “Sneeze,” Surprising Study Shows

By Karl Gruber

They don’t exactly say achoo, but sponges can “sneeze,” according to a new study that shows the simple aquatic creatures are more complex than previously thought. 

Sponges are stationary animals, found in both marine and fresh water, that lack nervous and digestive systems. The porous invertebrates have a central cavity called an osculum, where wastes are released into water and then washed away. Not much of an exciting agenda. (Watch a video of the sponge sneezing.)

sponge picture
A sponge used in the experiment. Photograph by Sally Leys and Danielle Ludeman

But there’s more there than meets the eye. Scientists have shown that sponges can respond to their environment thanks to a bunch of fixed, fingerlike structures called cilia, located within the osculum. (See “Antarctic Glass Sponges Live Life in Fast Lane.”)

Humans also have cilia that are used in sneezing: When we breathe in foreign particles, sensors in our noses and sinuses detect the particles. The sensors signal the cilia—tiny, hairlike paddles that line our nostrils and sinuses—to move to expel the irritants.

When these “fingers” detect something odd, like chemicals in the water, they send a signal to make the sponge contract its whole body in a sneezelike behavior that jets out water and chemicals.

“When I first began experiments for this study, I was quite surprised with just how responsive sponges are to their environment—sometimes even the slightest vibration would cause the sponge to sneeze!” said study co-author Danielle Ludeman of the University of Alberta.

Rethinking Brain Evolution

The finding is unexpected, experts say, since sponges don’t have a single sensory cell.

“This is a very exciting and comprehensive study that clearly demonstrates that sponges are more sophisticated,” said Gert Wörheide, a sponge-evolution expert from Ludwig-Maximilians University in Munich, Germany, who wasn’t involved in the study, published January 12 in the journal BMC Evolutionary Biology.

In fact, the cilia may serve as a kind of sensory organ for the primitive sponge—possibly the first instance of complex sensory systems in evolutionary history. (See pictures of strange-looking sea creatures.)

Discovering such a sensory system in a primitive animal like the sponge may also shed light on the evolution of the brains of other organisms, scientists say.

“The sneeze is a delightful behavior,” said study leader Sally Leys of the University of Alberta, “and one that is a great tool for understanding how coordination systems may have arisen during the evolution of early multicellular animals.”


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Meet the Author
I am a scientist with a Master of Science from the department of Ecology, Evolution and Behaviour at the University of Minnesota, and a versatile science communicator. Reviewing the primary literature and writing a clear and concise articles is an ability now embedded in me, as I have been doing this since I started working in the research realm, more than 10 years ago. I am comfortable working with strict deadlines and working under pressure. I have experience writing for various audiences, as seen from my articles from National Geographic, Science Now, New Scientist and The Munich Eye, aimed at lay audiences. Then my articles from Lab Times, The Lancet, GEN, and The Pain Research Forum, provide good examples of work aimed at more educated audiences. From these writing experiences you can see I have a strong commitment to meet deadlines and a great capacity to understand complex topics and produce clean, high-quality articles. I have also served as a reviewer for PLoS One and Journal of Heredity, and I currently work as a freelance Academic Editor for Cactus Communications, where I edit articles aimed at peer reviewed journals. I also have experience writing research grants and peer reviewed papers, since my time as a Bachelor student. Finally, I currently work (pro bono) as the Science and Technology Editor for The Munich Eye, where I am in charge of the content of this section. In this role, I identify relevant articles from the primary literature, assign articles and edit the work of freelance writers and publish their work on a daily basis at our online presence at For the print edition, besides the content, I also manage the outline of the articles that go into print. TME is currently on hold due to re-structuring.