Underwater creature looks like an under-cooked cake
Published: March 19, 2007
OK. I’m thinking of a loggerhead that’s 36 inches wide, and about 2 feet tall. Before you say it’s too easy a riddle to guess, consider this: It’s not a sea turtle and doesn’t even know how to swim. That’s trickier, huh?
It’s grayish to look at, but only because its natural brown color lies concealed under coats of sediment. The largest species of its kind, it’s shaped roughly like a cylinder that narrows around the base.
All right, here’s a better clue. You’ll find it hanging around in underwater colonies from North Carolina south to the West Indies. The loggerhead sponge is actually a virtual metropolis of tinier, colonial creatures that make up the fascinating world of sponges.
If you were diving in search of this loggerhead, what you’d look for would be something stuck fast to the ocean floor resembling an angel food cake, or more accurately, a cake taken too soon from the oven, that fell. But even though this fallen-cake similarity seems a dead giveaway for spotting loggerheads, it’s not so simple.
Seems there’s another sponge in the ocean that fancies to mimic our cake-like sponge, and its nickname is in fact “cake sponge.”
To make matters worse, even its common name, loggerhead sponge, matches ours. Only the scientific names vary. While our loggerhead is Speciospongia vesparia, the cake sponge is known in science circles as Ircinia strobilinia.
But to tell them apart without Latin, simply observe their outer surface. Where ours contains wavy contours like the lunar landscape, cake sponge’s surface has countless little peaks, like a tightly closed pinecone. Loggerhead has a wet-wood texture, and cake sponge is more, um spongy.
Continuing the cake comparison, pretend you’re frosting two similar cakes. On one, smooth your spatula in curvy, flat swirls. That’s our loggerhead. For the other, give your icing swipe an outward flourish, the way you’d pull peaks to finish frosting coconut cake.
Hmm. Are you getting hungry?
When our sponge wants to eat, it’s really a family affair. In fact, loggerhead sponges are so big, they can harbor as many as 16,000 tiny snapping shrimp living within one specimen’s canal system. That’s a lot of mouths under one roof.
Because sponges are the simplest many-celled creatures, they operate under a one-for-all code of house rules.
Each individual cell has its own assigned task. It may not seem a very important job, but all together they comprise a pretty impressive machine.
Basically, it amounts to a fine-tuned plumbing factory. Between cell multitudes, a system of canals runs through it. Sponge pores admit water, which passes through collar cells. These fellows each give the water a whack with a tiny flagellum, or minute paddle, sending it on its way.
The resulting current affords simplistic life-support, complete with oxygen exchange. Some cells glean food from the water, while others digest it.
They may not swim, or frequent our dunes in nesting season, but loggerhead sponges are fascinating critters just the same.
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