Chaetognatha

This chapter describes the taxonomy of Chaetognatha, a small phylum of exclusively marine organisms with approximately 150 species currently recognized, of which about 70 are pelagic. Chaetognatha are also known as arrow worms because of their shape and quick darting movements in the water. The chapter covers their life cycle, ecology, and general morphology. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.