Fig. 2

Stylized sequences of inversion processes in different multicellular volvocine species. Schematic representation of midsagittal cross sections of embryos of (a) Gonium pectorale [18, 38], (b) Pandorina morum [37, 38] and Eudorina elegans [16, 38], (c) Pleodorina californica [20], (d) Volvox carteri [38, 39, 51] and (e) Volvox globator [38, 53]. It should be noted that the overall deformation of the cell sheet of P. californica in (c1-c8) has been described previously by Kikuchi [20]. However, Kikuchi mentioned pre-inversion movements in stage (c2), which have never been observed in our studies (see main text). a-e The side of the cell layer that is outside in the adult configuration and from which the flagella will emerge is presented in brown, and the side of the cell layer that is inside in the adult configuration and where the reproductive cells are located, is presented in green. Light micrographs of several volvocine species at adult stages are shown in Fig. 1 and in Additional file 1. Scale bars: (a-c) 10 μm; (d, e) 20 μm