Style (zoology)

Illustrated dissection of the mussel Anodonta, showing the crystalline style ("st") in black
Mussel of the genus Anodonta, with style ("st") shown in black
Illustrated dissection of the mussel Lampsilis, showing the crystalline style ("st") in cross-section
Mussel of the genus Lampsilis, with style ("st") shown in cross-section

A style, sometimes referred to as a crystalline style (though there are no other biological kinds), is a rod made of glycoprotein located in the midgut of most bivalves and some gastropods which aids in extracellular digestion. It consists of a protein matrix coated with digestive enzymes secreted by the style sac in the animal's stomach. When feeding, its projecting end is scraped against the stomach wall and abraded, thus releasing the enzymes.[1]

When subjected to starvation or desiccation, some bivalves have been known to re-ingest this organ.[2]


  1. Ruppert, Edward E.; Barnes, Robert D. (1994). "The Molluscs". Invertebrate Zoology (6th ed.). Saunders College Publishing. p. 436. ISBN 0030266688.
  2. Hameed, P. Shahul (1987). "In vivo dissolution and reformation of crystalline style in certain intertidal bivalve molluscs". Mahasagar bulletin of the national institute of oceanography. 20 (2): 135–138.
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