Published by the American Geophysical Union as part of the Antarctic Research Series, Volume 3. This handbook, dealing with the Polychaeta Errantia of the Antarctic, is the first of two parts; the second part will deal with the Polychaeta Sedentaria. Together, the two books contain basic information on all Antarctic polychaetes; included are all known records south of the fiftieth parallel, and some farther north into sub-Antarctic areas. Generally, Gough Island, Tristan da Cunha, and some other islands south of New Zealand have not been included.

The species of Myzostomidae consist of small (a few mm long) aberrant polychaetes usually found as parasites on or in crinoid or ophiuroid echinoderms. They may occur far more abundantly than the published records indicate, since they are easily overlooked and may fall from the hosts when disturbed.

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 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.

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.