When the substance was applied to the tips of the lobster antennules, used for smelling, the lobsters were unable to detect an enticing, pungently-scented shrimp juice presented to them.
NEWS: Snot Affects Sense of Smell
To figure out why, the scientists measured electrical activity in the lobsters' chemosensory and motor neurons. These neurons stopped firing in the presence of the snotty gunk.
The researchers next isolated amino acids from the substance, but found that they alone had no affect on the lobsters. In fact, the lobsters' neurons "fired robustly" in reaction to the "delicious shrimpy aroma."
When the scientists mixed the amino acids with the sticky substance carboxymethylcellulose, aka cellulose gum, the lobsters again were fooled. Like sticking a wad of chewing gum on a human nose, it blocks odors from reaching aroma receptors.
The lobsters are usually left in dismay, preening and cleaning themselves while the sea hare slithers away.
Image: A sea hare that just released the inky, mucus-like defense substance; Credit: Colin Brown/Flickr