ABSTRACT
Early postlarval stages may differ from larval and adult phases of the life cycle in such characteristics as body size, morphology, molting frequency, growth rate, nutrient requirements, behavior, and habitat. Primarily by way of recent studies, information on these qualities in early postlarvae has begun to accrue, information which has not been previously summarized.
The change in form (metamorphosis) that occurs between larval and postlarval life is pronounced in some decapod groups but subtle in others. However, in almost all the Decapoda, some ontogenetic changes in locomotion, feeding, and habitat coincide with metamorphosis and early postlarval growth. The postmetamorphic (first postlarval) stage, herein termed the decapodid, is often a particularly modified transitional stage; terms such as glaucothöe, puerulus, and megalopa have been applied to it. The postlarval stages that follow the decapodid successively approach more closely the adult form. Morphogenesis of skeletal and other superficial features is particularly apparent at each molt, but histogenesis and organogenesis in early postlarvae is appreciable within intermolt periods. Except for the development of primary and secondary sexual organs, postmetamorphic change in internal anatomy is most pronounced in the first several postlarval instars, with the degree of anatomical reorganization and development decreasing in each of the later juvenile molts. Anatomical change during metamorphosis and the next few postlarval stages usually consists of degeneration of some anatomical features, redirection of some existent structures, and addition of some new structures. Examples of such processes can be seen in the early postlarval development of neurosecretory organs, musculature, muscle innervation, digestive organs, and even pigmentation patterns.
Comparative studies of early postlarvae may be of use in further resolving relationships between decapod taxa. To date, such relationships have been based primarily upon morphological comparisons of larvae or adults.
