Meeting Abstract

P2.59  Friday, Jan. 4  Sensory cells in sponges: evidence for flow sensors in the sponge aquiferous system? LEYS, SP; ELLIOTT, GRD*; BENTLEY, AG; University of Alberta; University of Alberta; University of Alberta gelliott@ualberta.ca

Sponges are benthic suspension feeders that are usually considered to lack tissue level organization, epithelia, sensory cells and behaviour. The demonstration that coordinated contractions of the canals function to expel wastes in the freshwater sponge Ephydatia muelleri prompted us to examine the morphology of the contractile canals. Scanning and transmission electron microscopy revealed sealed epithelia lining the sponge outer and inner surfaces. Use of the fluorescent lipophillic vital dye FM 1-43 showed that cells forming epithelia are static � they do not migrate in and out of the layer as is often suggested. Furthermore, a survey of the canal epithelia revealed occasional cells with paired cilia 4�m long, and all cells forming the inner lining of the osculum had paired cilia. Cilia (but not flagella of choanocyte chambers) labeled strongly with FM1-43 and live observations of cilia in canals and the osculum showed they were not motile. A brief survey of several other demosponges also revealed ciliated cells lining oscula epithelia. We propose that these cells may act as flow sensors detecting changes in water velocity and allowing the sponge to contract canals correspondingly.