Isogamy

Different forms of isogamy: A) isogamy of motile cells, B) isogamy of non-motile cells, C) conjugation (isogamy in the broad sense)

Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), and is found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or female. Instead, organisms that reproduce through isogamy are said to have different mating types, most commonly noted as "+" and "−" strains.