Byssus(redirected from Byssal thread)
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(1) An excretion of the byssal gland, found in the so-called feet of many bivalve mollusks. Immediately upon expulsion, byssus hardens and forms durable silky filaments by which mollusks fasten themselves to underwater objects. In antiquity a special cloth, vysson, was prepared from the byssus excreted by the large mollusk pinna.
(2) A roe disease of freshwater fish caused by certain fungi of the genera Saprolegnia and Achy la.