(Left) Radula of the deep sea limpet, Neomphalus fretterae, Family Lepetidae
     (Right) Radula of the slit shell mollusc, Scissurella crispata, Family Scissurellidae
Scanning electron micrographs; reprinted courtesy of  Dr. Carole S. Hickman,
Museum of Paleontology, University of California, Berkeley CA.                  .

The deep sea limpet's tongue, or radula (above, left) is used to scrape algae off rocky surfaces, and it is strong enough to bore a deep-set scar into the rock to which the limpet attaches (see the superfamily, Patellacea). The recurved tooth is hardened with iron and silicon oxides at its tip, in effect a sharp rasping tool. By comparison (above, right), the feathery structure of the slit shell mollusc's radula lacks hardened teeth. It is more suited to sweeping and filtering fine organic debris from the soft sands along the bottom, where this mollusc normally lives --a   mode of living like that of the other slit shell molluscs (see, for example, the Pleurotomariidae family).

 

(Right) The array of horny teeth shown belong to the radula of the Oyster Drill, Urosalpinx, a member of the Murex family noted for boring drill holes into heavy shells of mussels and other molluscs. The left and right ranks of teeth are hooked, and the middle tooth shows three cusps. Like all gastropods, the radular teeth are continually renewed from top to bottom, as they are worn away. In the case of Urosalpinx, rather than depending on silicon- or iron-hardened radular cusps, drilling is facilitated by secretions of an accessory salivary gland used to soften shell materials.

Scanning electron micrograph reprinted from an article by M. R. Carriker, American Zoologist 9:917-933, 1969; courtesy of the Society for Integrative and Comparative Biology.

 

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