RS-like immunoreactivity in the epidermis of sea cucumbers. A. Peroxidase-antiperoxidase immunohistochemistry with the RS-K10 antiserum showing strong immunolabelling of the apical region of tentacle epidermis in E. fraudatrix. B. Immunofluorescent microscopy with the AFRU antiserum reveals intense immunolabelling (green) of the apical surface of the podial epidermis in H. glaberrima. Nuclei are stained with Hoechst (blue). C. Immunoelectron (RS-K10 antiserum) micrograph of an epidermial cell of E. fraudatrix showing strong labelling of the apical surface (double arrowhead) and less prominent labelling of the lateral surfaces (arrowhead) of the cell. er, cisternae of the endoplasmic reticulum. Scale bars = 50 μm in (A) and (B), 1 μm in (C).