January 16, 2014
Sneezing Sponges Suggest Sensory-Like Response
[ Watch The Video: Sneezing Sponges Caught On Camera ]
Ranjini Raghunath for redOrbit.com - Your Universe Online
Sponges are marine creatures that don’t have sense organs, a spine, a stomach or a nervous system. All they have is a long, central column called the osculum making up a flexible body that twists and turns to let water, oxygen and nutrients flow in and out. Biologists consider them to be among the most primitive multicellular creatures on the planet.
Yet these immobile ocean-bed creatures can sneeze – a trait which is more characteristic of highly advanced animals – according to surprising new results from a study published in the journal BMC Evolutionary Biology.
Most animals and birds sneeze when tiny, hair-like extensions inside their noses sense foreign particles. It turns out that these sponges also use similar, hair-like paddles to sense debris or chemicals in the water.
These paddles, called cilia, line the inner wall of the osculum. Once they detect a disturbance in the water, they send a signal to the sponge similar to how nerve cells work in other animals. The sponge reacts by contracting its whole body and 'sneezing' out a jet stream of water and chemicals.
“The sneeze can tell us a lot about how the sponge works and how it’s responding to the environment,” said Danielle Ludeman, lead author and University of Alberta graduate student. “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?”
The researchers spent hours using different drugs to irritate the sponges, observe the process using fluorescent dye and capture the sneezes on video.
The discovery raises new questions about how sensory organs evolved in animals, says Sally Leys, senior author and University of Alberta evolutionary biologist.
“For a sponge to have a sensory organ is totally new,” she stated. “This does not appear in a textbook; this doesn't appear in someone's concept of what sponges are permitted to have.”
This type of sensory system may be unique to the sponge or maybe a remnant of a common sensory mechanism once shared billions of years ago by all animals, she added.