According to a new research report released by Canadian scientists, American lobsters use jet propulsion to gain extra speed as the walk across the ocean floor. The lobster can produce 27 to 54mN of thrust, which is comparable to that produced by the pectoral fins of proficient swimmers like the Bluegill sunfish (Lepomis macrochirus) and Surfperch (Embiotoca jacksoni).

On the abdomen, the American lobster has tiny paddle-like structures, formally known as pleopods, which it can fan to create a wake that propels it forward. To understand why the lobster fans its “paddles”, graduate student Jeanette Lim and Professor Edwin DeMont of St Francis Xavier University in Antigonish built a mechanical model which replicates the moving parts of the lobster belly.

“No one had actually measured how much force the American lobster’s pleopods could produce,” says Lim. “We just took the abdomen of a lobster, emptied out the tissues, and hooked up eight mini servomotors bought from a robotic toy company in California to the pleopods.”

To image and measure how the plepods affected the surrounding water, the researchers used a technique called particle image velocimetry.

“Once we saw the flow visualisations, we were surprised with how large the wake was,” says Lim, now studying for her PhD at Harvard University in Boston, US. “The pleopods on American lobsters (Homarus americanus) are relatively broad and paddle-shaped compared to pleopods on crayfish, for example. But they are still fairly diminutive and rather flimsy appendages when you consider the size and toughness of the rest of the body. So we were surprised their beating produced a sizable wake with thrust that was on par with forces produced by the fins of some swimming fish.”

The results have been published in the Journal of Experimental Biology.