Figure 6.

Cephalic disc invaginations in a 7-day-old pilidium of Micrura alaskensis. A, A' Confocal images of the pilidium larva stained with phalloidin (white) and hoechst (orange). Anterior up. A. A z-projection of the entire larva, looking into the mouth. A'. A sub-stack (8 μm thick) of the same larva, which highlights the paired cephalic disc invaginations (arrowheads), which originate from the outer epidermis of the pilidium i.e. above the ciliated band. B. A diagram of the pilidium larva in lateral aspect (anterior to the left) illustrating the plane of sectioning (orange line). See also additional file 2 -- Movie 2.