S1-1.10 Jan. 4 In situ measurements of glass sponge pumping: testing the current-induced flow hypothesis LEYS, S.P.*; YAHEL, G.; Univ. of Alberta; Univ. of Victoria email@example.com
Flow through sponges (Porifera) is thought to be enhanced by ambient current due to Bernoulliís principal, pressure differential, viscosity entrainments, or a combination of the three mechanisms. Vogelís test of this phenomenon suggested that current augmented by fanning live and inactivated (by killing in freshwater) sponges increased flow through the sponge. Glass sponges are an ideal subject with which to re-examine the hypothesis. Individuals are large (up to 1m tall), chalice-shaped animals, with a cavernous atrial cavity and a body wall less than 1cm thick that houses the flagellated chambers. We used Accoustic Doppler Velocimeters (ADVs) to measure flow velocities from 3 sponges and ambient water at 165m depth on a glass sponge reef near Vancouver, British Columbia. Week-long ADV records illustrated that exhalent flow corresponded to local tidal rhythms (measured with a nearby current profiler). However, at times the sponge pumping pattern deviated from the ambient flow suggesting that glass sponges do control excurrent flow velocities independently of ambient flow, and at the same time can take advantage of Vogelís principal of current-induced flow. However, glass sponges are syncytial and can arrest pumping following mechanical stimulation, regardless of ambient flow, as was shown in both lab and field experiments. Furthermore, fluorescent dye applied to dead sponges was not drawn through the inert skeleton, as would be implied by Vogelís hypothesis. Evidence from other sponge classes (Calcarea and Demospongiae) suggests that cellular sponges can also control flow through the animal by constriction of incurrent openings (ostia) and canals. Our experiments imply that while sponges can take advantage of current-induced flow, flow through these animals is largely controlled by their complex physiology.