Body growth and shape regulation by neuropeptides and other neuroactive peptides in insects

Animals exhibit species- and stage-specific variation in body size and shape. Body size depends on initial size, growth rate, and duration, and is influenced by intrinsic and extrinsic factors such as sex, genetics, nutrition, and temperature. Body shape is further influenced by the mechanical and chemical properties governing morphogenesis at cellular, tissue, and organismal levels. These processes are particularly well understood in insects, where genetic and environmental effects on body growth and shape are largely restricted to juvenile stages, coordinated by networks of local and systemic signals that ensure species- and sex-specific outcomes. Here, we review advances in our understanding of how neuropeptides and other neuroactive peptides regulate body size and shape by controlling tissue growth, feeding behaviors, and stage-specific morphogenetic behaviors. The molecular mechanisms underlying many aspects of body growth and shape plasticity remain unclear, but neuroactive peptidergic signaling pathways are likely to play key roles.