Annelida is a diverse group of animals, commonly referred to as segmented worms and currently comprising around 14000 described species. Found in most marine and freshwater areas, annelids have also successfully occupied many subterranean habitats. This volume documents annelid reproduction in the context of their phylogenetic relationships. It pre

The fascination of the Annelida to scientists lies in the beauty of their structures and the functionality of their body plan, the tremendous adaptive radiation which has made it possible for these animals to colonize almost all marine, limnic and terrestrial biotopes. In doing so they have evolved a great variety of life forms, and their reproduction and development are correspondingly diverse, with many modes and patterns unique in the animal kingdom. In this special volume recent progress in this broad research area is presented by 26 specialists, in general through surveys or treatments of selected examples. Some of them review important annelid taxa such as the Nereididae, Syllidae, Spionidae, Cirratulidae, Clitellata, and Pogonophora; others analyse reproductive and developmental structures and phenomena in annelids, e.g. segmental organs, sex pheromones, oogenesis, mating systems, sperm types, life cycles, larval settlement, cleavage and symmetry of embryos, or discuss controversial approaches to annelid systematics. The book will be of interest to all zoologists who work with annelids as well as to embryologists and other researchers in reproductive biology.

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.

Embryology and Phylogeny in Annelids and Arthropods ...

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.