Surface of Freshwater Sponge Gemmules

Surface of freshwater sponge gemmules. Gemmules are encysted spheres of thousands of sponge cells, and have a protective layer around their outside surface. Sponges can slowly move along (1 to 4 millimeters a day) by the amoeboid crawling of the marginal cells. The forces generated at the crawling margin not only move the sponge, but these forces also produce continuous rearrangement of the sponge's internal anatomy, including its skeleton of glassy spicules (thin glassy shards). This form of locomotion may be unique to sponges. Harris and Bond also discovered that the geometrical pattern of flow and propulsion of water through the interior of sponges is much different than previously thought.

Image credit: Professor Calhoun Bond, Greensboro College, North Carolina