Archerd Shell Collection > Shell Classes > Gastropoda > (Fissurellidae)

Family: Fissurellidae (Keyhole Limpets)

Despite a very similar shell, which permits them to strongly resist wave attack on exposed rocks, the keyhole limpets differ internally and externally from their cousins, the true limpets, or Patellacea. In both cases, a flattened foot acts like a strong suction disk, which adheres them to rock surfaces. Both move about in search of food, drawing in water around the foot, and they live either as scrapers of small detritus or as herbivores. In fissurellas, the volcano top is the exit port for waste products, rather than a mantle opening below the shell, as in the patellas. The internal organs of keyhole limpets are also modified to permit an exit channel through the body for waste products leaving at the top.
Megathura crenulata, whose shell is shown (below right) is one of the largest known keyhole limpets. As can be seen in the linked site (below)  a grayish mantle completely covers the shell in the live mollusc, leaving only the keyhole visible.
Of considerable interest is the commercial aquaculture of Megathura crenulata for the extraction of its hemolymph. The purified product, Keyhole Limpet Hemocyanin (KLH) has a long history of biomedical use as an immune potentiating molecule and carrier protein in the making of vaccines for cancer and other immunologic disuorders.
Class: Gastropoda
Clade: Vetigastropoda
Superfamily: Fissurelloidea
Family: Fissurellidae
Major Genera
  • Genus: Clypidina
  • Genus: Diodora
  • Genus: Emarginella
  • Genus: Fissurella
  • Genus: Hemitoma
  • Genus: Lucapinella
  • Genus: Macroschisma
  • Genus: Megathura
  • Genus: Puncturella
  • Genus: Rimula
  • Genus: Tugali
  • Genus: Zeidora
Diodora_aspera.JPG (74751 bytes)
Diodora aspera (Rathke, 1833) 
Rough Keyhole Limpet


Megathura_crenulata.JPG (62267 bytes)
Megathura crenulata (Sowerby, 1825)
Great Keyhole Limpet


(8th picture down):

Megathura crenulata
Great Keyhole Limpet

Archerd Shell Collection > Shell Classes > Gastropods > (keyhole limpets)