LEYS, SP; TOMPKINS, GJ; University of Alberta; University of Alberta: Glass sponges arrest pumping in response to increased sediment loads

Glass sponges are unusual in having mostly syncytial rather than cellular tissues. This structure allows them (in the absence of a conventional nervous system) to propagate electrical signals that control their feeding current. Here we show that sediment added to a flow through sea water tank causes both cloud (Aphrocallistes vastus) and boot (Rhabdocalyptus dawsoni) sponges to arrest feeding. Single doses (10 – 500mL) of sediment slurry added topically to a sponge in 1 or 2.5 L flow through tanks cause instant arrest of pumping. Typical arrests in both sponges take 2 minutes before full recovery occurs. Both sponges respond to sediment less than 25 um in size, but arrests are shorter than responses caused by whole sediment slurry. Continual application of sediment less than 25 um causes several sequential arrests of 8-10 minutes duration at intervals of 3-15 minutes, and an overall gradual reduction in pumping rate. The rate of pumping remains minimal until application of sediment is stopped, after which recovery to full pumping rate may take up to 12 hours. The data show that glass sponges are physiologically sensitive to increased loads of sediment in their environment.