Loggerhead 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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Vase sponge showing skeletal texture
Courtesy of Dr. Anthony R. Picciolo, NOAA NODC, public domain

About Sponges (Phylum Porifera): Skeleton

Sponges have an internal skeleton, but it is not made of bone like ours. Their skeletons are made of stiff, mineral rods called spicules, or a matrix of strong but flexible protein called spongin, or both. Spicules may be loosely scattered in the body tissue of a sponge, gathered into little bundles, or arranged in symmetrical patterns to form a structured skeleton. You can judge a sponge by its spicules. They come in many shapes, from as simple as toothpick-straight to complex, branching stars. The end of each spicule is specialized too; it may be pointed, flat, shovel-like, or even look like a mushroom cap. By using microscopes to look at spicules (which are tiny), scientists are often able to identify the type of sponge they came from. Given that the spicules are often all that remain of a dead sponge, this is quite handy.

Yellow picasso sponges (Staurocalyptus sp.)
Courtesy of NOAA/Monterey Bay Aquarium Research Institute, public domain

About Sponges (Phylum Porifera): Reproduction

Sponges achieve reproduction in a whole variety of ways. All sponges can reproduce sexually, meaning that egg and sperms cells get together for fertilization of the egg. How that happens varies from sponge to sponge. Usually, fertilization occurs outside of the female sponge in a meet-up of egg and sperm cells in the ocean (good luck!). Some sponges have internal fertilization, where the sperm cell swims to fertilize the egg inside the female. She may then lay eggs (oviparity) or release live larvae that have developed inside her body (viviparity). Most sponges are hermaphrodites, able to be both males and females. They might act as both sexes at the same time, or more likely one sex first and then the other. Many sponges sidestep fertilization at times by reproducing asexually. They either pinch off buds of new cells or break off clumps from their body. In either case, the cells reattach attach to a substrate and grow into adult sponges.

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