BOND, C.; Greensboro College: Time-Lapse Studies Of Propagated Contractions In Sponges

For many years, sponge biologists have occasionally reported on slow �contractile waves� in intact sponges, but these propagated contractions remain poorly understood. Time-lapse microscopy of marine and freshwater sponges, which is reported here, provided an opportunity to re-examine these contractions. Sponge contractions were observed in several species, and they were best seen in the canals near thin margins, as well as in long protruding bud-like extensions. Contractions propagated at speeds of 25-50 µm/minute through the sponge. Contraction frequency varied a lot but appeared to be most prevalent in the long extensions (3-6 times/hour). Propagated canal dilation was the most notable change in the marginal contractions, and this and other evidence suggest that some contractions are linked to changes in water flow in the canals. These internal contractions are followed by significant rearrangement of the involved canals. Propagated contractions also appear to be connected to the lengthening and expansion of the bud-like extensions. These contractions thus could be a major contributing mechanism for the morphological plasticity of sponges.