Tube sponge (Leucosolenia sp.)
This weird creature looks like the skeleton of a flea, but it's not even closely related. It is a sponge, a primitive animal that has a variety of cousins in the Northwest.
Sponges range in form from upright tubes to balls and encrusting mats. This little fellow (about 2 inches long) was found under a float at the Boston Harbor Marina. It ranges from British Columbia to Southern California. It differs from other sponges in the numerous small tubes that give it a branching appearance. It also tends to be whitish in color.
You probably are familiar with large sponges that are used as household tools for cleaning windows and counter tops and washing cars. Those species were harvested from tropical locations until the resource was depleted. Today, most sponges found for sale are artificial.
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Sponges can be considered the next step up from single-celled organisms. They have several cell types cooperating to form a large, multicell structure. One cell type forms microscopic openings for incoming water and lines the walls of the water-carrying canals. In the canals are chambers that house other cells with two functions: collars that catch plankton and flagella that move the water through the canals.
The water exits from the sponge through large, easily seen openings. Some cells make a supporting material called a spicule whose chemical composition and shape are so varied that they are used to identify sponges. Sponges can reproduce through budding, in which parts of the mass break off and grow another individual, or through sexual reproduction, in which there is a fusion of genetic material between two individuals.
David W. Jamison is a marine biologist and Boston Harbor resident.