Figure 4

(a) Relative abundance of the [M-H]⁻ ions of the different molecular species of phosphatidylethanolamine (PE) present in embryos of Carcinus maenas and Necora puber at stage 1 and (b) at stage 3. (c) General structure of PE. (d) Major molecular species of PE identified by liquid chromatography – mass spectrometry in negative-ion mode in the embryos of C. maenas and N. puber. Error bars represent standard deviation of three independent samples. P values for each significant statistical test performed are represented in the figure with a number, with significant differences between crab species being represented on the top of the graph bars and significant differences between stages of the same crab species being represented within the bar of stage 3 embryos. Significant interaction between species and stage is represented with an i on the top of stage 1 bars. (Post hoc Tukey HSD, 1: P = 0.0061; 2: P = 0.0045; 3: P = 0.0441; 4: P = 0.0133; 5: P = 0.0237; 6: P = 0.0003; 7: P = 0.0109; 8: P = 0.0346; 9: P = 0.0181; 10: P = 0.0440; 11: P = 0.0099; 12: P = 0.0074; 13: P = 0.0389; 14: P = 0.0167; 15: P = 0.0003; 16: P = 0.0032; 17: P = 0.0089). Interaction species vs stage (i): m/z 736.4 (P = 0.0274); m/z 774.4 (P = 0.0146); m/z 776.4 (P = 0.0310); m/z 792.4 (P = 0.0389); m/z 798.2 (P = 0.0466).