Venus' Flower Basket

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.

Cup-shaped glass sponge (Euplectella sp.)
Courtesy of Brooke et al., NOAA-OER, HBOI.; Florida Coast Deep Corals Expedition 2005 , public domain

About Glass Sponges (Class Hexatinellida): Habitat

Glass sponges live on the bottom of the ocean, as deep as 2,000 meters (about 6,500 feet) or more. They have special structures to anchor them and keep themselves upright. Those that live on sand, for example, have long tufts of fibers sticking out of their bases. Glass sponges are adapted to really cold water and are most abundant in polar regions such as Antarctica. The only time they are found close to the sea surface is when surface waters are chilly, such as below ice or where deep waters are upwelling to the surface. They were found in a Mediterranean cave, for example, only meters from the surface, thanks to a trapped mass of cold water. Glass sponges tend to live in clusters and have formed a reef in British Columbia that towers nearly 20 feet above the seafloor.

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Tube-shaped glass sponge (Euplectella aspergillum) in a yellow sponge
Courtesy of North Atlantic Stepping Stones Science Party, IFE, URI-IAO; NOAA/OAR/OER

About Glass Sponges (Class Hexatinellida): Senses

Sponges do not have nervous systems, but a glass sponge has a unique set-up that allows it to conduct electrical impulses around its body in response to stimuli from outside. As its body cells divide, they do not separate completely. They remain connected by bridges of cell material, resulting in a mega-cell that looks like a spider web. This web of soft tissue (called a syncytial network) is wrapped around a mineral skeleton for support. When the mega-cell gets stimulated by something outside, an impulse travels rapidly from one part of the sponge to another, across the cell-cell bridges. This function is similar to what our nervous system does, and may allow a glass sponge to respond to signals from its environment.

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