Here is a sponge.
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No, a live sponge, not the dish washing kind.
Scientists say it might do something that humans do too. What could a human and a creature scientists rank exceedingly low on the animal kingdom evolutionary totem poll have in common?
Researchers filmed video of sponges sneezing. (Image source: YouTube)
As one might imagine though, a sponge sneeze is very different than a human sneeze.
The ability of a sponge to sneeze when exposed to an irritant is something that surprised scientists because they were not thought to have a sensory organ.
"For a sponge to have a sensory organ is totally new," researcher Sally Leys, a Canada Research Chair in Evolutionary Developmental Biology who co-authored the study, said in a statement. "This does not appear in a textbook; this doesn't appear in someone's concept of what sponges are permitted to have."
The study led by Danielle Ludeman, a master's student at the University of Alberta, found that the freshwater sponges, which do not have conventional muscles or nerves, possess cilia (small hair-like structures) in its excretory structure (the osculum), which are sensory. This then, could show that the osculum is "a sensory organ that is used to coordinate whole animal responses in sponges," as the study published in the journal BMC Evolutionary Biology put it.
Various microscopic images of the sponge and its cilia. (Image source: Ludeman et al. BMC Evolutionary Biology)
From an evolutionary standpoint, scientists think this could "represent the first step in the evolution of sensory and coordination systems" in these basic animals.
"The sneeze can tell us a lot about how the sponge works and how it's responding to the environment," Ludeman said in a statement in the university's news release. "This paper really gets at the question of how sensory systems evolved. The sponge doesn't have a nervous system, so how can it respond to the environment with a sneeze the way another animal that does have a nervous system can?"
Now, you might be picturing the filter-feeding animal squirting out a short burst of fluid and sediment that could have been irritating it, similar to a human sneeze in action. But, Ludeman's observations found that sponge sneezing takes between 30 to 45 minutes and involves the whole body of the sponge expanding and then contracting.
In her experiments, Ludeman and Leys coaxed the sponges to sneeze by putting different stimulants in the water. Ludeman filmed the results in time-lapsed footage. Check out this example:
"[…] the finding of such an organized array of sensory cells in sponges provides new insight into possible mechanisms of evolution of early sensory systems," the study concluded.
“This is a very exciting and comprehensive study that clearly demonstrates that sponges are more sophisticated,” said sponge expert with the University of Munich Gert Worheide, who was not involved with this study, said, according to National Geographic.