RS-like immunoreactivity in the ectoneural part of the radial nerve cord, transverse sections. Dashed line shows the border between the ectoneural (en) and hyponeural (hn) parts of the radial nerve cord. A, B Low-magnification view of the radial nerve cord of H. glaberrima showing (A) Immunofluorescent microscopy with the AFRU antiserum (green) and nuclei stained with Hoechst (blue) and (B) the immunofluorescence combined with a Hoffman DIC image. Note the intensely labelled immmunoreactive material overlaying the apical surface of the ectoneural neuroepithelium. C. High magnification view of the radial nerve cord of H. glaberrima with a locally dilated lumen of the epineural canal (ec). AFRU-positive labelling (green) is clearly associated with the apical surface of the ectoneural neuroepithelim (en) and with the non-neural epineural roof epithelium (re). Note also immunoreactive cell bodies (arrowheads) and dotted labelling in the neural parenchyma. The inset shows a high magnification view of an immunoreactive cell body within the ectoneural parenchyma. D, E. Peroxidase-antiperoxidase immunohistochemistry with the RS-K10 antiserum on paraffin sections of the radial nerve cord of E. fraudatrix. D. Labelling associated with the apical region of the ectoneural neuroepithleium and with epineural roof epithelium (re). Note the deposition of the immunopositive material on the apical surface of the neuroepithelium (arrows). E. Labelled cell bodies (arrowheads) and processes (double arrowheads) within the ectoneural parenchyma. Scale bars = 100 μm in (A) and (B), 50 μm in (C), 10 μm in (C inset), (D), and (E).