Fig. 3

Experimental design for drug exposure experiments. Diagram depicts the early developmental stages of C. pergamentaceus from zygote to larval stage L2 (larval schematic adapted from [29]). Drug exposures were conducted during multiple time intervals. Exposures to U0126 (orange bars), DMH1 (teal bars), and dorsomorphin dihydrochloride (green bars) were conducted during the 4 cell to late cleavage stage (T1), and the late cleavage stage to early gastrula time intervals (T2). Exposures to SB431542 (purple bars) were conducted during the 4–32 cell (T1); 16–32 cell (T2); 32 cell to late cleavage stage (T3); and late cleavage stage to early gastrula (T4) time intervals. After removal of the chemical inhibitor, embryos were raised in sea water for approximately 72 h to L2 larvae, and then fixed for phenotypic analysis (vertical gray line on right hand side). Horizontal gray lines indicate duration of the experiment. Cells labeled as 2d, 3D, and 4d have been identified as organizers in other spiralians (see text)