Figure 12

Esophageal pouches which give rise to the juvenile foregut, and provisional nephridia in Micrura alaskensis. Confocal sub-stacks of the juvenile inside the pilidium larva between "complete proboscis" and "hood" stage, stained with phalloidin; juvenile anterior at upper left on A, C and D, and at bottom left on B. A. A z-projection of thirteen 1-μm mid-sagittal confocal sections showing one of the thick-walled pouches (arrowhead) of larval esophagus (es) sandwiched between the cerebral organ (co) and the larval stomach (st). This stack also shows one of the cerebral ganglia (cg), ventral commissure of the brain (vc), and dorsal commissure of the brain (dc). The space dorsal to the proboscis (pb) is the blastocoel (bl), which is traversed by the muscle-retractor of the apical organ (upper right corner). B. A z-projection of ten 1-μm frontal sections through a different larva at a similar developmental stage, showing both of the bilaterally symmetrical esophageal pouches (arrowheads) between the two cerebral organs and the larval stomach. The stack also shows the ventral commissure of the brain connecting the two cerebral ganglia, and one of the nephridioducts (nd). C. Same specimen as on A; a z-projection of ten 1-μm sections slightly more lateral compared to those on A. This stack passes through the cerebral organ (co), cerebral organ canal, the thick nerve (con) which connects the cerebral organ to the cerebral ganglion, and one of the provisional nephridia (in the center of boxed area) sandwiched between the larval esophagus, the larval stomach, and the cerebral organ. D. The boxed area in C magnified to show the three finger-like branches (arrowheads) of the nephridium. See also additional video files 6 and 7 -- Movie 6 and Movie 7.