According to recent concepts, the intervals of ontogeny in fishes are divided into four periods: embryo, larva, juvenile, and adult periods (Balon 1985; Youson 1988). Youson (1988) proposed three pathways of ontogeny between the embryo and the adult (Fig. 1). Direct development from the embryo period leads to a juvenile period (type 2) or an adult period (type 1), whereas indirect development (type 3) involves a larval period that has a metamorphic phase (first metamorphosis) leading to the juvenile period. The (first) metamorphic phase is obligatory during indirect development, beginning with the initiation event and ending with the completion of the climax event, at which time the juvenile form and behavior are present (Youson 1988). The initiation and climax events involve the morphogenetic processes of transformation, regression, and differentiation from primordia. A second metamorphosis may occur between juvenile and adult periods.
KeywordsEarly Life History Otolith Growth Otolith Microstructure Metamorphic Phase Conger Myriaster
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