ABSTRACT
Through the course of evolution by natural selection, annelid larvae have well adapted to their particular niches and may little resemble the adults of their own species, neither morphologically nor physiologically. Larvae and adults — although they share the same genome — show distinct biological and ecological differences — often using different habitats and food sources. Despite their ecological dissimilarity, the success of the one form as the early phase of the life cycle determines the existence and reproduction of a later phase (Hadfield 1998). These sorts of reproductive patterns comprising two or more ecologically distinct phases are termed complex life cycles (Strathmann 1990).
