Planet Earth

Shrimp Couples Use Sponges as Gingerbread Houses

DiscoblogBy Joseph CastroAug 1, 2011 10:03 PM

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Up-close views of Typton carneus's shear-like tools.

In Hansel and Gretel

, two ravenous children stumble upon a house made entirely of sugary goodness, and begin to chow down with abandon. But the kids' journey quickly turns sour, as the owner of the house, a wicked witch, tries to cook them for dinner. While the story seems to be a cautionary tale, it turns out that finding and living in an edible house can actually be pretty sweet—at least in the animal kingdom. Researchers in Prague have now learned that some tiny shrimp in the Belize Barrier Reef

dine on fire sponges

, their homes, by first tearing off pieces of tissue with claws not unlike those of Edward Scissorhands

. Scientists have long known that many species of invertebrates

inhabit marine sponges. But in many cases, biologists have little insight on the relationship between host and squatter. Do shrimp and sponge benefit equally from the arrangement, or are the shrimp more like parasites, who take, take, take, and never give back? In the current study, published in the journal PLoS One

, researchers decided to take a closer look at fire sponges and their common inhabitants, the tiny shrimp Typton carneus. The team began by inspecting the appendages of the shrimp with a scanning electron microscope

. Rather than the normal claws you see on other crustaceans like lobsters, the researchers found well-worn "tools," which resembled scissors, on the shrimps' second legs. And when they dug into the shrimps' stomachs, the scientists learned that the crustaceans had been chomping on their spongy shelter and little else. Of course, that's not all that surprising—if you lived in a delicious gingerbread house (without a lurking witch), wouldn't you eat it? But these discoveries don't automatically mean that the shrimp are parasitic; other evidence may actually point to a semi-symbiotic

relationship between the marine animals. For example, the researchers found that only one male and one female T. carneus typically live in each sponge, suggesting that the love birds drive away other would-be squatters, preventing the sponges from being overrun. Males, with their single, large claw, may also fend off predators looking to make a quick snack out of their squishy homes. Aside from this, the researchers pointed out that the shrimps' tiny incisions probably don't leave any lasting damage because sponges can regenerate lost tissue. But if they had a vote, the sponges would likely prefer not to be cut up in the first place. [via ScienceNOW

] Image courtesy of Sandford et. al, PLoS One

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