Annelida Basal Groups and Pleistoannelida, Sedentaria I

This book is the first in a series of three volumes in the Handbook of Zoology series which cover morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. Annelida, the segmented worms, comprise one of the most important invertebrate taxa in the marine environment, but they also can be found in fresh water and terrestrial environments. Annelids constitute important members of the respective food chains. Although only comprising approximately 16,500 species they show a remarkable diversity comparable for instance with that observed in crustaceans. This diversity could only be achieved by the plasticity of their bauplan constituting prostomium, followed by a number of primarily identical modules, the segments, and the pygidium. Species are usually of median size and do not exceed a few cm in length. However, their size range is much wider some of the smallest adult metazoans known with body dimensions of less than 0.2 µm belong to this group as well as species exceeding body lengths of more than 3 m. The number of segments varies accordingly from less than ten and several hundred. Primarily their life cycle comprises a planktonic larva, the trochophore, and a benthic adult. In this first volume special emphasis is laid on morphology and anatomy as well as development and other topics and will give a modern synthesis of our knowledge about this important taxon.