Pattern and Diversity in Reproduction and Development
This chapter offers an overview of invertebrate embryology and larval development, outlining a consistent scheme for classifying the diversity of larval development modes. It addresses patterns in larval development, looking to correlates and constraints for further understanding. Patterns during early development historically have been organized into a dichotomous scheme; the results of this organization have been particularly useful in studies of the phylogenetic relationships among invertebrates. The urge to categorize and classify is inexorably tied to man’s wish to understand pattern. The chapter offers a classification scheme for larval development composed of four categories: mode of larval nutrition, location or site of development, the dispersal potential associated with a particular developmental type, and the morphogenesis involved in development. Within most major invertebrate taxa there is a distinct association between brooding and small adult body size. Energetic costs of different larval nutritional modes have been debated extensively through modeling efforts and by collection of empirical data.