Fig. 1. Acridine orange (red)- and DAPI (yellow)-stained nematocysts in tentacles of Hydra. (A) Overview of distal tentacle stained with AO. (B) High magnification of AO stained tentacle. The small green fluorescent structures are nuclei of the nematocytes. (C) High magnification of DAPI-stained tentacle. (D) High magnification of ethanol fixed AO stained tentacle showing exploded capsules. The matrix of exploded stenoteles and isorhizas is empty and unstained; the matrix and everted tubule of exploded desmonemes is filled with pG and stained by AO. (A-C) fluorescence micrograph; (D) phase contrast and fluorescence micrograph. Bar, 20 µm (A); 10 µm (B-D).