Sea Hares Beat Lobsters With Sticky Substance

By Pierre Dumont , Mar 28, 2013 02:06 PM EDT

If you matched a lobster against a sea hare, you'd think the winner would be pretty obvious.

That may not be the case, however, given new research from Georgia State University. The researchers conducted a study revealing that sea hares, sluglike creatures that roam the ocean, foil lobsters by emitting a white, sticky substance called opaline that clogs the lobster's sensory organs. The lobster is often too preoccupied trying to cope with the smell to prevent the sea hare from escaping.

Sea hares, or "Aplysia," are marine mollusks whose name comes from the two long, earlike features on their heads. At their largest, they can grow up to 4.4 pounds.

While the researchers knew that the sea hare's chemical emissions could prevent them from becoming a lobster meal, they didn't know whether the emissions blocked the lobster's sensory organs, located on the antennae, or created signals preventing the lobster from smelling food.

To come to their conclusion, they examined both sea hares and Caribbean spiny lobsters ("Panulirus argus"). They isolated the sticky portion of the sea hares' opaline by removing its water-soluble component, thereby removing the amino acids and other chemicals that may have played a part in dulling the lobsters' chemosensory receptors. They then painted the sticky portion onto the lobsters' antennules. When the lobsters were presented with yummy "shrimp juice," they were uninterested in the food, as indicated by chemosensory and motor neuron response measured by the researchers. They repeated the experiment three times with other substances, ultimately finding that opaline is effective in saving sea hares from the clutches of lobsters.

"Opaline sticks to antennules, mouthparts and other chemosensory appendages of lobsters, physically blocking access of food odors to the predator's chemosensors, or over-stimulating (short term) and adapting (long term) the chemosensors," the study claims. "our results indicate that opaline reduces the output of chemosensors by physically blocking reception of and response to food odors, and this has an impact on motor responses of lobsters."

The study is published in the Journal of Experimental Biology.

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