Origin and Evolution of Metazoan Cell Types

The evolution of animal diversity is strongly affected by the origin of novel cell and tissue types and their interactions with each other. Understanding the evolution of cell types will shed light on the evolution of novel structures, and in turn highlight how animals diversified. Several cell types may also have been lost as animals simplified – for example did sponges have nerves and lose them? This book reveals the interplay between gains and losses, and provides readers with a better grasp of the evolutionary history of cell types. In addition, the book illustrates how new cell types allow a better understanding permitting the discrimination between convergence and homology.

Sally Leys is Professor and Canada Research Chair in Evolutionary and Developmental Biology at the Department of Biology, University of Alberta in Edmonton. She has authored or co-authored dozens of peer reviewed scientific journal articles. Her lab studies sponges to understand how key features of animal body plans — including polarity, gastrulation and tissues, the germ lineage, nerves and muscle — may have arisen during evolution. This work takes a whole organism approach, from ecology to physiology and molecular biology. In the lab they use a practical and tractable model system, sponges hatched from gemmules, with which they can look for genes expressed, manipulate phenotype, and study behaviour and signalling in the petri dish.

Andreas Hejnol is the Research Group Leader for "Comparative Developmental Biology of Animals" at Sars International Centre for Marine Molecular Biology at the University of Bergen in Norway. He has also authored or co-authored dozens of peer reviewed scientific journal articles. His group studies a broad range of animal taxa using morphological and molecular tools to unravel the evolution and development of animal organ systems. Besides established morphological methods like confocal microscopy they use 3D timelapse microscopy (4D-microscopy) and single blastomere injections of cell tracers to study the cell lineage of embryos of mainly marine invertebrates. Molecular approaches used in his lab include the study of gene expression patterns and experimental methods to unravel the genetic framework underlying the formation of different organ systems, such as the CNS, the alimentary canal and other organs. Large scale sequencing approaches are used for gene discovery and are also used for the phylogenetic placement of the specific species. Research focuses on the description of the development regarding cell lineage and gene expression includes understudied taxa such as local bryozoans, brachiopods, nematomorphs, aplacophoran molluscs, platyhelminthes, priapulids, polyclad flatworms etc. Molecular functional approaches are used to study the development of acoels, rotifers and gastrotrichs. Further collaborative approaches address the use phylogenomics to resolve metazoan phylogeny.