Neurohormonal Regulation of Metamorphosis in Decapod Crustaceans

Crustaceans are a subphylum of arthropods that comprise a diverse group of species classified into six classes. We will focus on the commercially important order Decapoda which includes crabs, crayfishes, krill, lobsters, prawns and shrimps. In this chapter, we will cover neuroendocrine regulation in metamorphosis, with particular attention on the recent advances in the Eastern spiny lobster Sagmariasus verreauxi. However, neuroendocrine pathways regulating metamorphosis are generally similar in decapod species and could be used interchangeably. Key biomolecules used in metamorphosis, the crustacean hyperglycemic hormone and methyl farnesoate, also regulate other critical physiological process in decapods, such as reproduction and sex differentiation. Many gaps in our knowledge can be highlighted and some will be covered in this chapter, in particular concerning metamorphosis. Metamorphosis is a complex process accompanied by extensive re-structuring of cells and tissues and is facilitated by extensive changes in the genetic constituents that are being expressed as the process unfolds. ‘Omics’ tools that have become widely available nowadays, enable taking snapshots of different stages through the process in order to identify key factors with expression, which could suggest involvement in the process. The procedure to identify the genes and annotate their function is cumbersome and is hindered by the lack of a genome in decapods; up to 70% of the gene lists that are generated in decapods using omics tools are unknown. Since many of these unknown factors change through metamorphosis, one could argue that we know far less about the process than what we don't know. With this regard, metamorphosis represents an exciting area to better understand complex biological processes and through that to decipher the function of unknown factors.