ABSTRACT
To understand the origin and evolution of animals, we need not only model organisms among the earliest-branching animal lineages but also among their closest unicellular relatives. This is not an easy enterprise, since most of the classical model organisms are bilaterian animals, and so the techniques may not work on these unicellular taxa. In the last decade, and despite the challenge, efforts have been made to develop genetic tools among different unicellular relatives of animals. This chapter introduces the four clades of the unicellular relatives of animals (Choanoflagellata, Filasterea, Ichthyosporea and Corallochytrea/Pluriformea) and reviews the current state of their available genetic tools. Importantly, all four of these clades have different developmental modes with temporal multicellular life stages and have genes that were previously thought to be animal specific. The development of genetic tools in these unicellular relatives of animals opens up novel research avenues to understand the evolution from protists to multicellular animals.
