Richelia (R) symbiotic within the diatom Rhizosolenia
Richelia symbionts within the diatom Hemiaulus. The upper panel is a conventional micrograph (phase contrast illumination) of part of a Hemiaulus membranaceous chain, and the lower panel is the same specimen, this time using epifluorescent illumination to pick out the N2-fixing symbionts (two per diatom cell). Scale bar = 8 microns. Photographs courtesy of D. Caron. Reproduced with permission from (T Villareal et al, Mar Ecol Progr Ser, 1991, 76:201)