ELLIOTT, Glen R D; LEYS, Sally P; University of Alberta; University of Alberta: Sponge Coughing: Stimulated contractions in a juvenile freshwater sponge, Ephydatia muelleri

Porifera are multicellular animals that represent the most basal branch of the metazoa and are thought to have diverged from the last common ancestor of the metazoa 600 million to one billion years ago. Within the metazoa sponges are the only phylum that lack a nervous and muscular system, thus they have developed novel systems to compensate. The freshwater sponge, Ephydatia muelleri lives in calm, low flow environments that deal with high levels of debris that clogs its aquiferous system. Digital video time-lapse microscopy, histology and scanning electron microscopy has shown that freshwater sponges display a series of coordinated contractions to remove clogging debris such as ink from the sponge aquiferous system. E. muelleri has contractile cells called myocytes that are organized within a single epithelial layer that surrounds the entire aquiferous canal system and are thought to be responsible for the conduction and propagation of the contraction. The fact that sponge contractions occur in a stereotypical and repeatable manner suggests: 1) that sponges are capable of responding to environmental stimuli, like other metazoan animals; 2) that a coordinated behavioural response to stimuli is possible even in the absence of neurons or junctions that would allow electrical signalling between cells; and 3) that coordination and contractile systems may have first evolved within the Porifera.