Chapter 1 - Introduction: Larval Development, Evolution, and Ecology

Abstract

This chapter presents an introduction to larval development, evolution and, ecology. The life history of many organisms includes a larval stage that is morphologically distinct from the adult's and/or that inhabits a different environment from the adult. The aquatic tadpole and the terrestrial frog are prime examples. Some species display indirect development; larvae must metamorphose to transform into, or be replaced by, adults. Larval evolution provides the key to unlocking metazoan evolution and diversification. Yet, because of larval adaptations (caenogenesis), only some larvae have provided useful information for reconstructing phylogenetic histories and evaluating evolutionary relationships. Embryos contain cells and developmental programs for both larval and adult structures. These may be completely separate, as in insects (in which adult cells are set aside in imaginal disks within the larval body), or they may be admixed, as in amphibians. Some larvae, especially those of insects, can enter a phase of dormancy that permits them (and indeed the population or species) to survive what otherwise would be lethal environmental conditions.