| The studies presented here used live, intact sponges (belonging to several marine and freshwater species) in order to explore relationships between cell behavior and the behavior, morphology, and anatomy of sponges. Intact sponges were studied with time-lapse cinemicrography and scanning electron microscopy. Techniques borrowed from studies on living tissue-culture cells (e.g., flexible rubber substrata, interference reflection microscopy) were also applied to live sponges.; Active locomotion of entire sponges across solid substrata was studied in relation to the behavior of the sponge's component cells. Sequential tracing of sponge outlines on aquarium walls demonstrated that individuals of eight species of sponge can crawl at speeds of up to 160 {dollar}mu{dollar}m/hr. Microscopic examinations (using the techniques mentioned above) of crawling sponges indicate that sponge locomotion is not achieved by the sequential extension, adhesion, and contraction of processes; nor do sponges move by peristaltic contractions. Rather sponge locomotion is achieved by the cumulative, amoeboid locomotion of the cells that compose the sponge's leading margin. This mode of organismal locomotion provides new explanations for the plasticity of sponge morphology, seems not to have been reported from other metazoans, and has significant ecological implications.; In addition to these external changes, sponges were observed to undergo continuous internal changes in their canals and other structures. My observations suggest that this constant, anatomical remodeling, as well as the external changes, can be explained as a result of interactions between moving cells and the physical forces generated in the sponge by water pressure and tension. Internal water pressure, produced by the pumping choanocyte cells, seems to control canal organization. Tension, which is produced mainly by the sponge being pulled by its cells at the leading margin, appears to orient the sponge's external internal structures, and may even stimulate reformation of functional sponges from initially disorganized sponge cell aggregates. |
