Arrhenotoky

Definition

A mode of parthenogenesis in which unfertilized haploid eggs develop into males, while fertilized diploid eggs develop into females. This produces a haplodiploid (arrhenotokous) sex-determination system where paternal genome presence determines femaleness.

Etymology

From Greek arrhēn 'male' + tokos 'birth, offspring'

Example

Honey bees (Apis mellifera) exhibit arrhenotoky: queens lay unfertilized eggs that become haploid drones (males) and fertilized eggs that become diploid workers or queens (females).

Synonyms

• arrhenotokous parthenogenesis
• haplodiploidy (in context of sex determination)

Related Terms

• thelytoky
• deuterotoky
• Haplodiploidy
• Parthenogenesis
• sex determination
• Hymenoptera

Usage Notes

Arrhenotoky is the dominant sex-determination system in Hymenoptera, many mites and ticks (Acari), and some thrips, beetles, and scale insects. Contrast with thelytoky (all-female parthenogenesis) and deuterotoky (both sexes from unfertilized eggs). The term is primarily used as a noun; the adjectival form is 'arrhenotokous.' Not all haplodiploid systems involve true parthenogenesis—some arise from chromosome elimination—but arrhenotoky specifically denotes development from unfertilized eggs.