Scallops are hermaphroditic; capable of switching sexes. Both sexes produce roe, whose coloring depends upon the parent's. Red roe is that of a female, and white, that of a male. Spermatozoa and ova are released freely into the water during mating season and fertilized ova sink to the bottom. After several weeks, the immature scallop hatches and the larvae drift until settling to the bottom again to grow. They reach sexual maturity after several years. they are found throughout much of the world's oceans. Like the true oysters, they have a central adductor muscle, and thus their shells have a characteristic central scar marking its point of attachment. However, the adductor muscle of scallops is larger and more developed than that of oysters because they are active swimmers and the sole migratory bivalve. Their shell shape tends to be highly regular. This picture was taken at Finnart Loch Fyne.

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Picture by John Nicolson