In this Special Issue, we address the state of the art of the systematics of the main annelid groups and the improvements in the diversity they hold, with special emphasis on the latest discoveries in well-studied areas, expeditions to unsurveyed areas or environments, or the use of novel techniques that allow for the improvement of biodiversity knowledge. We are hoping that this Special Issue will provide a platform facilitating a review of current knowledge on the subject, identifying current research problems, as well as indicating directions and research trends for the future.

Polychaetes are very common marine worms belonging to the Annelid family that are of interest to marine biologists and invertebrate zoologists. The book presents an understanding of the biology of this group with many illustrations.

Annelids (the segmented worms) exist in a remarkably diverse range of mostly marine but also freshwater and terrestrial habitats, varying greatly in size and form. Annelida provides a fully updated and expanded taxonomic reference work which broadens the scope of the classic Polychaetes (OUP, 2001) to encompass wider groups including Clitellata (comprising more than a third of total annelid diversity), Sipuncula, and Thalassematidae (formerly Echiura). It reflects the enormous amount of research on these organisms that has burgeoned since the millennium, principally due to their use as model organisms to address wider and more general evolutionary and ecological questions. Beginning with a clear introduction to the phylum and an outline of annelid taxonomy, this authoritative text describes their collection, the methods to ensure their optimal preservation, and an overview of anatomy with its relevant terminology. The core of the work comprises 77 fully up-to-date taxonomic chapters, informed by anatomy and the latest molecular phylogenomic evidence and carefully organised based on a new, robust phylogenetic hypothesis. Lavishly illustrated throughout with hundreds of previously unpublished high-resolution colour images and SEM micrographs, the sheer beauty and diversity of the annelids is nowhere better presented. Annelida is the definitive reference work for annelid biologists, whilst being of interest to a broader audience of invertebrate zoologists, systematists, and organismal biologists.

The Fourth Edition of The Light and Smith Manual continues a sixty-five-year tradition of providing to both students and professionals an indispensable, comprehensive, and authoritative guide to Pacific coast marine invertebrates of coastal waters, rocky shores, sandy beaches, tidal mud flats, salt marshes, and floats and docks. This classic and unparalleled reference has been newly expanded to include all common and many rare species from Point Conception, California, to the Columbia River, one of the most studied areas in the world for marine invertebrates. In addition, although focused on the central and northern California and Oregon coasts, this encyclopedic source is useful for anyone working in North American coastal ecosystems, from Alaska to Mexico. More than one hundred scholars have provided new keys, illustrations, and annotated species lists for over 3,500 species of intertidal and many shallow water marine organisms ranging from protozoans to sea squirts. This expanded volume covers sponges, sea anemones, hydroids, jellyfish, flatworms, polychaetes, amphipods, crabs, insects, snails, clams, chitons, and scores of other important groups. The Fourth Edition also features introductory chapters on marine habitats and biogeography, interstitial marine life, and intertidal parasites, as well as expanded treatments of common planktonic organisms likely to be encountered in near-to-shore shallow waters.

In July 2001 experts from all around the world met in Reykjavik, Iceland to discuss various issues of polychaete biology. In particular the latest developments in cladistic inference of polychaete phylogeny were presented. Some studies applied recent molecular techniques, revealing unknown genetic relationships between the different families of polychaetous annelids. This volume is of interest to specialists and students seeking an introduction to the latest developments in the field of systematics and ecology of polychaetous annelids. This book is one in a series presenting results from the International Polychaete conferences.