(Image courtesy of Sally J. Bensusen/Visual Science Studio and Natural History Magazine, copyright 2001)

Many spiny lobster species make sound by rubbing a plectrum (an extension off of the base of each antenna) over a file which is located on each side of a plate below the eyes. Surprisingly, the plectrum is made of soft tissue and the file is macroscopically smooth. This means that spiny lobsters don't make sound like most arthropods, which rub a hard pick over a series of bumps to make sound. Instead, spiny lobsters use the friction between the soft plectrum and sticky-smooth file to make sound pulses. The use of frictional, "stick and slip" properties to generate sound vibrations is similar to the way that stringed instruments make sound. Spiny lobsters are the first animals to be described that use a "stick and slip" mechanism of sound production.

The image to the left is a light microscope image which shows the soft tissue of the plectum's surface. This plectrum is about 4 mm wide.

The image to the right is is a file, approximately 14mm long, with a macroscopically smooth surface. The plectrum has a knob that sits in the long groove visible on the file. The plectrum thus rubs over the file using the knob to guide its path, just like a sliding door.

A stringed instrument generates sound when the bow rubs over each elastic string (see below). As the bow rubs over the string, the bow periodically sticks to the string due to frictional forces. In spiny lobsters, the elastic, soft-tissue plectrum rubs over the file's surface. Just like the stringed instrument, the plectrum periodically sticks and slips to make sound.

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 Publication links:

• Patek, S.N. 2002. Squeaking with a sliding joint: mechanics and motor control of sound production in spiny lobsters. Journal of Experimental Biology 205: 2375-2385.
• Patek, S.N. 2001. Spiny lobsters stick and slip to make sound. Nature 411: 153-154.

Press Links:

• BBC
• Natural History Biomechanics Column by Adam Summers
• Duke Research