Glass Sponge

Associated Smithsonian Expert: Klaus Ruetzler, Ph.D.

Dr. Klaus Ruetzler examines sponges maintained in a running-seawater system at the wet lab in Carrie Bow Cay, Belize.

Photo credit: Molly K. Ryan

Dr. Klaus Ruetzler is a research zoologist and curator of sponges in the Department of Invertebrate Zoology at the Smithsonian National Museum of Natural History. His current research focuses on the diversity and ecology of sponges from submarine caves on the Mesoamerican Barrier Reef of Belize (Central American Caribbean). He is also working on a book describing 40 years of Smithsonian research on this coral reef ecosystem for which he founded the Smithsonian Carrie Bow Marine Field Station in 1972. He grew up in Austria and first became interested in sponges when he explored submarine caves, using self-made scuba gear, in Croatia, Adriatic Sea, where sponges make up most of the colorful fauna. He turned his early observations into a dissertation and earned a doctorate at the University of Vienna. He was hired by the Smithsonian Institution when a position for a sponge specialist became available.

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This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Holding a glass sponge (Euplectella sp.)
Courtesy of Islands in the Stream Expedition 2002. NOAA Office of Ocean Exploration, photographer Bruce Moravchik, public domain

About Glass Sponges (Class Hexatinellida): Skeleton

The glass sponges get their name from their skeleton that is made of small rods or long, bristle-like fibers (spicules) made of silica, or glass. The sponge makes the glass with silicic acid it extracts from the seawater. Each spicule is a little spiny cluster consisting of four or six rods at right angles to each other, like a shape you could build with Tinker Toys. The fused spicules create a lattice structure that forms the vase-like shape of a glass sponge. The regular arrangement of the symmetrical spicules makes a glass sponge more symmetrical than most other sponges. The clusters can be highly ornamented with additional branching, creating beautiful skeletal lattices. The arrangement is also functional; it turns out a glass sponge skeleton is 100 times as stiff as an aluminum tube of the same size.

Rope sponge in a ball (Aplysina sp.)
Courtesy of NURC/UNCW and NOAA/FGBNMS, public domain

About Sponges (Phylum Porifera): Locomotion

Sponges do not move around much; they are considered to be sessile or fixed in one place. However, research has shown that some sponges can move slowly by shifting their cells in a coordinated fashion. They can reshape themselves to crawl along the seafloor or other surface. They extend parts of their bodies and contract others to achieve locomotion. However, if you attempt to watch a sponge moving, you will likely be disappointed. At best, they move tiny distances, like a couple of millimeters per day. Juvenile sponges are much more mobile. A sponge larva is a little ball of cells with hair-like extensions (cilia or flagella) that allow it to paddle around for a few days until it finds a place to settle down. Once settled, its cells transform to be more appropriate for a sessile organism.