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Lack of nervous system not to be sniffed at

Scientists have filmed a sponge sneezing, suggesting that even without a nervous system, these basic animals can sense and respond to their environment.

Sponges are the most basic form of a multicellular animal. They lack the nerves and digestive systems seen in other animals, relying on water flow through their canal system for their food and oxygen. Surprising findings, published in the open access journal BMC Evolutionary Biology suggest that sponges might be more sophisticated than we previously thought.

The researchers were investigating the effect of pharmacological stimuli on cilia found in sponges. These cilia are tiny finger-like projections which line a sensory organ called an osculum. They found that inhibiting or removing the cilia prevented the body-wide sneeze, suggesting that cilia are the trigger for a whole-body signalling mechanism. Further experiments also showed cilia grow before a new osculum, suggesting they may be necessary for the sensory organ’s function.

Danielle Ludeman from the University of Alberta says: ‘When I first began experiments for this study, I was also quite surprised with just how responsive sponges are to their environment - sometimes even the slightest vibration would cause the sponge to sneeze!’

Though sponges do not have traditional sensory or nervous systems, they were able to sense the stimuli applied by the scientists using only a cilium. The cilium appears to transmit signals across the entire sponge body to react to the stimulus, resulting in a coordinated response from the sponge – and this despite not having a nervous system. The authors think this suggests the evolutionary origin of complex sensory systems in higher mammals.

Dr Sally Leys from the University of Alberta says: ‘The sneeze is a delightful behaviour, and one that is going to be able to yield lots of information to us about how sponges respond to the different habitats they are in (shallow coastal, mangroves, deep sea with heavy currents), and we think it is also a great tool for understanding how coordination systems may have arisen during the evolution of early multicellular animals.

The footage was included in research published in BioMed Central’s open access journal BMC Evolutionary Biology. Example films of the sneezing reaction can be found here.

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Notes to Editor

1. Evolutionary origins of sensation in metazoans: functional evidence for a new sensory organ in sponges
Ludeman, DA, Farrar, N, Riesgo, A, Paps, J and Leys, SP
BMC Evolutionary Biology 2014, 14:3

Article available here.

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

2. Videos of the sponges can be found in this Dropbox with explanatory notes by Danielle Ludeman.

3. BMC Evolutionary Biology is an open access, peer-reviewed journal that considers articles on all aspects of molecular and non-molecular evolution of all organisms, as well as phylogenetics and palaeontology. @BMC_Series

4. BioMed Central is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector. @BioMedCentral 

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