PELAGIC DISSOCONCHS OF THE COMMON MUSSEL, MYTILUS EDULIS, WITH OBSERVATIONS ON THE BEHAVIOR OF THE LARVÆ OF ALLIED GENERA

Abstract

At the close of the larval or prodissoconch stage the young of Mytilus edulis which fail to secure immediate attachment may remain pelagic through the secretion of gas into the mantle chamber. Short distances may be covered through the aid of a holdfast secreted on the surface film or through holding the foot or the tentacles of the incurrent siphon in the surface film. The ability to bridge over the critical period of metamorphosis while remaining pelagic has been an important factor in securing the present wide distribution of the black mussel. Absence of a similar adaptation in the larvæ of other bivalves renders them still dependent largely upon chance in securing at the close of the pelagic period a proper substratum for attachment. This dependence upon the substratum is one of the chief barriers to the wide dispersal of the species.