Heterogamy

Definition

A reproductive condition characterized by the production of dissimilar gametes or the occurrence of distinct mating types within a species, encompassing both anisogamy (morphologically different gametes) and functional heterogamy (distinct sexes or mating strains). In arthropods, heterogamy underlies the evolution of separate sexes (gonochorism) and diverse mating systems, contrasting with isogamy where gametes are similar.

Etymology

Greek heteros (different) + gamos (marriage, union)

Example

In Drosophila fruit flies, heterogamy is expressed through anisogamy—small, motile sperm fertilizing large, nutrient-rich eggs—and through chromosomal sex determination (XY males, XX females), producing functionally distinct mating types.

Synonyms

• anisogamy (narrower, when emphasizing gamete size/shape difference)

Related Terms

• isogamy
• anisogamy
• oogamy
• gonochorism
• hermaphroditism
• Sexual dimorphism
• Parthenogenesis

Usage Notes

In modern usage, heterogamy often specifically denotes anisogamy (gamete dimorphism), but historically and in some contexts it refers more broadly to any system with distinct mating types. Contrast with isogamy, typical of many algae and some basal eukaryotes. In population genetics, heterogamy can also describe outbreeding or mating between unlike individuals; this sense appears in social science and plant breeding literature and should be distinguished from the reproductive-biology meaning.