This book is the fourth in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. It covers the most typical polychaetes, Phyllodocida, together with certain smaller taxa placed incertae sedis. This volume completes the polychaetous Annelida. Phyllodocida are often vagile, possess well-developed parapodia. Due to their broad and flat cirri these parapodia look like leaves in some taxa and leading to the name of the entire group. Many of its members are macrophagous and often predators. Accordingly most species possess elaborate sense structures such as sensory palps, antennae, eyes and nuchal organs. In certain species the eyes comprise thousands of photoreceptor cells and lenses most likely allowing forming true images. Phyllodocida typically possess an axial muscular pharynx called proboscis functioning as a kind of suction pipe allowing them to swallow and ingest their prey or other food. This pharynx may be armed with cuticular jaws and some species even possess venom glands. The probably most popular and important polychaete model organism, Platynereis dumerilii, belongs to this interesting group. Phyllodocida fall into two to three higher clades comprising about 25 families which represent more than one fourth of the polychaete diversity. One of these families, Syllidae, comprises about 700 valid species of mainly small size and may, therefore, represent one of the most complex and somehow difficult polychaete families on Earth.

This book is the third volume in a series of 4 volumes in the Handbook of Zoology series treating morphology, anatomy, reproduction, development, ecology, phylogeny, systematics and taxonomy of polychaetous Annelida. It is devoted to the remaining Sedentaria and the first branches of Errantia. These sedentary polychaetes are Terebellida and Arenicolida, all of which are tube-dwelling and deposit feeders. The tubes may be simple burrows stabilized by mucus or the tubes are highly sophisticated often really aesthetic structures build-up of sediment grains glued together by their secretion. Although the former possess anterior appendages used for collecting food particles, these are likely not modified palps rather than a new acquisition. Many of these species are adapted to occur within environments characterized by low oxygen supply and so many members of these taxa possess elaborated branchiae, usually positioned on a number of anterior body segments except for Maldanidae which look like bamboo sticks and thus earned their common name bamboo worms. Members of Arenicolida and Maldanida may occur in high abundance and as such they create biogenically graded sediment beds. The Errantia part starts with Myzostomida, a group of symbiotic animals associated with echinoderms which have been variously placed within the tree of life. As such they show numerous adaptations to this specific mode of life. The next group discussed within Errantia is Protodrilida, a taxon comprising four families of the former archiannelids which belong to the interstitial fauna. Most likely they evolved by miniaturization from larger ancestors. In contrast to typical errants they do not possess well-developed parapodia and antennae. This taxon is followed by Eunicida characterized by possession of a specific jaw apparatus situated ventrally in the foregut and associated with specific musculature. Also being a species rich group showing various feeding modes some of the smallest and the largest members belong to this taxon.

This book is the second volume in a series of 4 volumes in the Handbook of Zoology series treating morphology, anatomy, reproduction, development, ecology, phylogeny, systematics and taxonomy of polychaetous Annelida. In this volume a comprehensive review of a few more derived higher taxa within Sedentaria are given, namely Sabellida, Opheliida/Capitellida as well as Hrabeiellidae. The former comprise annelids possessing a body divided into two more or less distinct regions or tagmata called thorax and abdomen. Here two groups of families are united, the spioniform and sabelliform polychaetes. Especially Spionidae and Sabellidae are speciose families within this group and represent two of the largest annelid families. These animals live in various types of burrows or tubes and all possess so-called feeding palps. In one group these appendages are differentiated as grooved feeding palps, whereas in the other they may form highly elaborated circular tentacular crowns comprising a number of radioles mostly giving off numerous filamentous pinnulae. Often additionally colourful, the latter are also received the common names "feather-duster worms", "flowers of the sea", "Christmas-tree worms". Opheliida/Capitellida including five families of truly worm-like annelids without appendages represents the contrary. Their members burrow in soft bottom substrates and may be classified as non-selective deposit feeders. Molecular phylogenetic analyses have shown that Echiura or spoon worms, formerly regarded to represent a separate phylum, are members of this group. Last not least Hrabeiellidae is one out of only two families of oligochaete-like terrestrial polychaetes and for this reason received strong scientific interest.

This book is the first in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. This first volume covers members of the so-called basal radiation and the first part of Sedentaria. It is supplemented by chapters on the history of annelid research, their fossil record, and an introduction to the phylogeny of annelids and their position in the tree of life. In the latter chapter the history of their systematic is reviewed giving an almost complete picture of systematic-scientific progress especially in the past years which changed our view on annelid phylogeny dramatically. The most basal annelids, lately united as Palaeoannelida, represent two families of aberrant polychaetes formerly often suggested to be highly derived which now give us a fresh look on how the ancestral annelid may have looked like. These lack certain key characters such as nuchal organs and possess rather simple nervous systems which now likely represent primitive character states. In this basal radiation the first taxon of apparently unsegmented and achaetigerous animals is positioned, the Sipuncula. Most likely another group of platyhelminth-like and unsegmented and even chaeta-lees annelids, Lobatocerebridae falls into this basal radiation. The section of Sedentaria starts with Orbiniida, a taxon characterized by elongated, thread-like worms which do not have anterior appendages like palps and comprises several families representing members of the Meiofauna. These minute worms often inhabiting the interstitial spaces in marine sands are suggested to have evolved by progenesis. The second higher taxon is represented by Cirratuliformia comprising nine families of typical sedentary polychaetes each of which showing a remarkable variation of the annelid body plan. Members of this taxon usually exhibit many annelid characters but certain also lack the most typical prostomial appendages, the palps.

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.

This book is the fourth in a series of 4 volumes in the Handbook of Zoology series about morphology, anatomy, reproduction, development, ecology, phylogeny and systematics of Annelida. It covers the most typical polychaetes, Phyllodocida, together with certain smaller taxa placed incertae sedis. This volume completes the polychaetous Annelida. Phyllodocida are often vagile, possess well-developed parapodia. Due to their broad and flat cirri these parapodia look like leaves in some taxa and leading to the name of the entire group. Many of its members are macrophagous and often predators. Accordingly most species possess elaborate sense structures such as sensory palps, antennae, eyes and nuchal organs. In certain species the eyes comprise thousands of photoreceptor cells and lenses most likely allowing forming true images. Phyllodocida typically possess an axial muscular pharynx called proboscis functioning as a kind of suction pipe allowing them to swallow and ingest their prey or other food. This pharynx may be armed with cuticular jaws and some species even possess venom glands. The probably most popular and important polychaete model organism, Platynereis dumerilii, belongs to this interesting group. Phyllodocida fall into two to three higher clades comprising about 25 families which represent more than one fourth of the polychaete diversity. One of these families, Syllidae, comprises about 700 valid species of mainly small size and may, therefore, represent one of the most complex and somehow difficult polychaete families on Earth.

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.