by Amanda Kahn
First things first, what is a sponge? Check out one of my former blog posts that introduces you to a few important background facts: 1) sponges are animals, and 2) sponges are filter feeders. They can grow up as big masses, taking on the shape of spheres, blobs, vases, tubes, or plates. Alternatively, they can encrust, or grow over, rocks or sediments. One group of sponges follows a different strategy.
In the picture below, these animals are growing on what looks like an old abalone shell, and overgrowing that shell is Ophlitaspongia pennata (the orange sponge). There is another, yellow, sponge in this picture, but it has tubes that project out while the rest appears to be below the surface of the substrate. What’s going on here?
The answer is: the yellow sponge is a boring sponge (Cliona californiana, to be precise). Let me clarify what I mean by “boring sponge.” I do not mean that this is a snoozer of a sponge (One of Urban Dictionary’s definitions of boring is, “Like sleeping but with eyes open. When your [sic] tired and everything’s quiet and not fun.” Instead, I mean the OTHER definition of boring:
“Boring – to form, make, or construct (a tunnel, mine, well, passage, etc.) by hollowing out, cutting through, or removing a core of material.” —Dictionary.com
Boring sponges are known from back in the 1800’s, when New Jersey fishermen called them Bay-pumpkins (Leidy, 1889). Fishermen and scientists at the time observed that boring sponges excavated the shells of oyster and scallops, and later research found that boring sponges secrete chemicals that eat away at calcium carbonate over time. They can bore through mollusc shells, coralline algae, and even non-marine substances! In an article from 1879, John Ryder wrote:
“In 1871 a vessel laden with marble was sunk in Long Island sound, and according to Prof. Verrill, the boring sponge has penetrated the exposed parts of the blocks for a depth of two to three inches from the surface.”
The sponges tunneled two to three INCHES–about the length of a credit card–in solid marble! In spite of boring into calcium carbonate, these sponges are filter feeders like most other sponges. Boring sponges are found throughout the world, and are a common sight on the shells of live and dead molluscs in and around Bamfield. Keep an eye out for their bright yellow oscula protruding from tiny pores in the shells they grow on!
To learn more about boring sponges, check out this webpage from the Chesapeake Bay Program, and if you have questions or have more fun facts to share about boring sponges, leave them in the comments section below.
Leidy, J., 1889. The boring-sponge, Cliona. Proceedings of the Academy of Natural Sciences of Philadelphia 41, 70-75. Accessible at: http://www.jstor.org/stable/4061579
Ryder, J.A., 1879. On the destructive nature of the boring sponge, with observations on its gemmules or eggs. The American Naturalist 13, 279–283. Accessible at: http://www.jstor.org/stable/2449456