Annelida, a common and diverse group of marine invertebrates, populate habitats all over the world. However, many questions around their evolutionary relationships remain unanswered - AM scientists invited international colleagues to help!

Annelida is a diverse and abundant group of marine invertebrates that populate habitats all around the globe, from the highest mountains to the abyssal depths. The origins of all extant annelids are still being debated, but annelid-like fossils have dated back to the Cambrian period (approx. 543 million years ago). Genomic and transcriptomic studies have been essential in relating Annelida to the molluscs, branchiopods, nemerteans and phoronids.

Annelids exhibit a tremendous diversity in morphology, lifestyles and adaptations to different environments. The evolution of this diversity has occurred over a relatively short geological timeframe – and as such, unravelling the relationships within the annelids has remained difficult.

Coloured plate showing the diversity of annelids

Coloured plate showing the diversity of annelids.

Image: Maël Grosse
© Maël Grosse

Over the past two decades, many studies on the origins of annelids have been undertaken and to date, over 20,000 species of Annelida have been described. Although these studies have radically changed scientists' views on the evolutionary relationships within the group, much remains to be done.

We invited a number of researchers from all over the world to explore these enigmatic relationships, examine the latest discoveries within this group and address the systematics of the main annelid groups. This has culminating in the recent Special Issue: Systematics and Diversity of Annelids. We invited 46 colleagues from 16 countries and 37 institutions, representing researchers at all stages in their careers from graduate students, early career researchers, to senior researchers. This team of researchers truly highlights the international and collaborative nature of annelid research.

All 12 chapters are multi-authored and are international, with Australian Museum scientists and collaborators at the centre of the work. Maria Capa wrote three of the chapters and Pat Hutchings two, and together they wrote an historical overview and highlighted areas of future research. Other AM staff who contributed to this work include Dr Elena Kupriyanova who co-authored a chapter on “Fan worms: yesterday, today and tomorrow”. Chris Glasby, an AM Research Associate, coordinated a chapter on “Annelids, in extreme aquatic environments, diversity: and adaptations and evolution”. Pat Hutchings’s PhD student, Nicolas Lavesque from Bordeaux University, also contributed to one of the chapters on Terebellida.

Front Cover of: Systematics and Diversity of Annelids. Diversity.

Front Cover of: Systematics and Diversity of Annelids. Diversity.

Image: Maël Grosse
© Maël Grosse

Most of the chapters address major groups of annelids and provide an overview of their morphology and a history of their discovery, including the number of species described per decade, their biology and ecology, as well as highlighting their worldwide distribution and identifying geographical areas and habitats where major studies need to be undertaken. Throughout the Special Issue, there is a strong emphasis on the future directions to annelid research.

Importantly, this research highlights that many more Annelida remain to be described; further research needs to be undertaken in unsurveyed biogeographical regions, habitats and depths, and in new techniques of sampling, identifying and analysing biodiversity. Species considerations need to be afforded when studying molecular data that allow for distinction between similarly looking or identical specimens.

We suggest that anybody working on annelids or about to start working on this diverse group, should reach out to the research team and read this Special Issue. It must be stressed the international nature of annelid research must be considered in any future works, and how so much still remains to be done.

Dr Pat Hutchings, Senior Fellow, Marine Invertebrates, Australian Museum.

Dr Maria Capa, Research Associate, Marine Invertebrates, Australian Museum; and Ramon y Cajal Fellow, Departament de Biologia, Universitat de les Illes Balears, Spain.

Meagan Warwick, AMRI Project and Communications Officer, Australian Museum.

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We would like to thank all of the contributors to this volume on the Systematics and Diversity of Annelids many of whom have visited the Australian Museum at some stage in their careers which has built a very strong network of collaboration of annelid workers which greatly facilitated the development of this volume. Some of these were funded by Australian Museum Fellowships, Endeavour Fellowships, others received funding from their home institution. Maria originally worked at the Museum on a Fulbright Fellowship for 2 years and then returned on a 3 years ABRS/AM Postdoctoral Fellowship.