Tag Archives: senses

Curious sponge behaviour

In a little tidy-up of old files, I ran across a paper on sneezing sponges. This is not an April Fool’s joke – today is the 2nd of April. When we sneeze, we fill our lungs and then hold the air in while increasing the pressure on the lung. When we open up and let the air out, it rushes out, moving particles, mucous and irritants as it rushes. Sponges take in water all over their surface but the water exits through one hole. In order to rid themselves of particles and irritants, they close that single hole while continuing to take in water. When the exit is opened, the water inside comes out with some force.

Sponges are such primitive animals that they have no muscles and no nervous system. Until recently it was believed that they also lacked sense organs. But they do have a sense organ and that is how they are able to organize a sneeze. The exit hole (osculum) is lined with cells that have little hairs (cilia) protruding into the water stream. These cilia can sense grit and changes in flow. The cilia are of a type called ‘primary’; they cannot move but can sense being moved. Primary cilia are found in a number of sensory organs in other animals; for example, in our ears and the lateral line of fishes. The general molecular structure of primary cilia is more or less conserved over multicellular animals.

In the same way that the molecules needed for neurons and synapses are seen in organisms that have no nervous systems, this is another component of our nervous system that has a very ancient lineage.

Here is the abstract of the paper ( D. Ludeman, N. Farrar, A. Riesgo, J. Paps, S. Leys; Evolutionary origins of sensation in metazoans: functional evidence for a new sensory organ in sponges. BMC Evolutionary Biology, 2014; 14 (1): 3 ):


