Parthenogenesis

Definition

A mode of asexual reproduction in which embryos develop from unfertilized eggs without genetic contribution from a male parent. In insects, parthenogenesis occurs through several cytological mechanisms—automixis (restoration of diploidy via meiotic recombination) and apomixis (mitotic, clonal development)—and may produce exclusively female offspring (thelytoky), exclusively males (arrhenotoky), or both sexes (deuterotoky). Thelytokous parthenogenesis is common in aphids, phasmids, and some hymenopterans, often alternating with sexual generations in response to seasonal cues.

Etymology

From Greek parthenos (virgin, maiden) + genesis (origin, creation)

Example

The Indian stick insect Carausius morosus reproduces by obligate thelytokous parthenogenesis: all populations are female, and unfertilized eggs develop into genetically identical daughters that perpetuate the lineage indefinitely without males.

Synonyms

• virgin birth
• asexual reproduction by oogenesis

Related Terms

• thelytoky
• Arrhenotoky
• apomixis
• automixis
• cyclical parthenogenesis
• obligate parthenogenesis
• facultative parthenogenesis
• oviparity
• adenotrophic viviparity

Usage Notes

Distinguish parthenogenesis (development from an egg) from other asexual mechanisms such as fission, budding, or fragmentation. In entomology, 'cyclical' or 'heterogonic' parthenogenesis refers to the seasonal alternation of asexual and sexual generations seen in aphids and some gall wasps, whereas 'obligate' parthenogenesis describes species that have lost sexual reproduction entirely. The term is sometimes misapplied to hermaphroditic self-fertilization, which involves gamete fusion.