Figure 7
Development of the posterior two trunk ganglia in Hypsibius dujardini. Maximum CLSM projections of embryos labeled for acetylated α-tubulin in lateral view of successive stages (in (A-C)) and ventral view (in (D-E)). Solid arrowheads (in (A-D)) indicate longitudinal pioneering axons. Arrows (in (E)) point to neurons that may be associated with the hindgut or cloaca (cf. ref. [11]). (A) Development of the fourth trunk ganglion, which is delayed relative to that of the third trunk ganglion. (B) Beginning of pioneering axon growth in the fourth trunk ganglion anlage. Notice the proximity of the anteroventral cells to the fourth trunk ganglion due to the curved position of the embryo inside the egg. (C) Longitudinal pioneering axons (arrowheads) reach the anterior adjacent segment. (D) Detail of the developing central nervous system in the posterior region of an early-stage embryo. The fourth trunk hemiganglia anlagen are initially spaced far apart. (E) Late-stage embryo with peripheral nervous structures already present. The developing central fiber mass of the fourth trunk ganglion consists of several distinct commissures and fibers (open arrowheads). Abbreviations: av, anteroventral cells; lg, leg ganglion; g3 to g4, anlagen of trunk ganglia 3 to 4; pn, peripheral nerve. Scale bars: (A-C), 3 μm; (D), (E), 5 μm.