Conjugating protozoa. Light micrograph of two sexually-reproducing (conjugating) protozoa, Blepharisma undulans. Conjugation occurs when the two protozoa come together to swap or donate genetic material in their nuclei, the cells sometimes fusing into one. B. undulans is a ciliate protozoa, a type of creature which has two different types of nuclei. Only one of these, the micronucleus is involved in conjugation. Magnification: x125 at 35mm size.