Figure 1. Representative choanoflagellates analyzed in this study. ; Choanoflagellates have diverse morphologies, including single cells, multicellular colonies, and the production in some lineages of extracellular structures. (a) Diaphanoeca grandis, within a silica-based extracellular structure called a ‘lorica’. (b) Acanthoeca spectabilis, within lorica. (c) Codosiga hollandica, with a basal organic stalk. (d) A rosette colony of Salpingoeca rosetta; image courtesy of Mark Dayel. (e) Salpingoeca dolichothecata, within an organic extracellular structure called a ‘theca’. (f) Mylnosiga fluctuans, with no extracellular structure. (g) Didymoeca costata, within lorica. (h) Salpingoeca helianthica, within theca. (h’) A rosette colony of S. helianthica. All scale bars represent 5 µm. Prey bacteria are visible in most panels as small black dots. Images of all choanoflagellate species sequenced in this study can be found in Figure 1—figure supplement 1.