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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.”

Comments

  1. Anne
    United States
    January 14, 8:25 am

    More evidence of evolution. And more reason for me to be agnostic rather than atheistic. How can you explain all of the life forms on this planet? How can you explain the Universe? I hope that death brings an answer to my questions. I imagine/hope death to be an illumination.

  2. gradstudent
    January 13, 8:02 pm

    Maulise: This finding is surprising to the scientific community because sponges do not have nerves. You’re correct that there are simple animals without brains that detect and respond to stimuli, however they all have nervous systems. Phylogenetically speaking, sponges are basal to cnidarians (anemones), which are in turn basal to all of the worm phyla (basal = “more primitive” or “less derived”). Because sponges are the most basal animals, and thought to be similar to the common ancestor of all animals, this study has major evolutionary implications. P.S. The animals you mentioned do not have “an amalgamation of blood vessels in the general location of the ‘head’”.

  3. Peter Morgenroth
    Australia
    January 13, 7:59 pm

    Not new. There is a reference to it in Barnes, Invertebrate Zoology – 1st or 2nd ed; c.1960s

  4. Maulise
    January 13, 3:59 pm

    I really don’t see why this was found to be so surprising… There are many simple creatures with no brain that are able to actively and very sensitively respond to stimuli, such as the anemone, or even worms, though, granted, they have more complicated structure, however, they do not posses a ‘true brain’, only an amalgamation of blood vessels in the general location of the ‘head’.

  5. Ima Ryma
    January 13, 3:18 pm

    Sponge Bob blew out a great big sneeze.
    All of Bikini Bottom shook.
    Pet snail, Gary, meowed, ” Golly! Geez!”
    And gave Sponge Bob a puzzled look.
    The pineapple house dripped in snot.
    Sponge Bob was so proud of his blow.
    “Humans don’t think us sponges got”
    “The mindset to sneeze, doncha know!”
    “Sandy Cheek squirrel can spread the word,”
    “Next time she heads out of the sea,”
    “That humans again think absurd”
    “About how nature truly be.”

    A sneezing Sponge Bob doll now is
    Blowing away merchandise biz.