Sexual reproduction

Definition

Reproduction involving the fusion of two genetically distinct gametes—typically a smaller, motile sperm and a larger, non-motile egg—to produce a diploid zygote with recombined parental genomes. In arthropods, sexual reproduction alternates with or replaces asexual modes, generating genetic diversity that underlies adaptation, host–parasite coevolution, and the maintenance of deleterious-allele masking. Most insects and arachnids are obligately sexual, though some lineages have secondarily lost males or recombination (thelytoky, apomixis).

Etymology

Latin sexus (sex, division) + re- (again) + producere (to bring forth)

Example

In Drosophila melanogaster, sexual reproduction involves males transferring sperm via aedeagus to female spermathecae; the resulting zygote undergoes rapid syncytial divisions before cellularization, with recombination shuffling alleles during meiosis I.

Synonyms

• amphimixis
• gametic reproduction

Related Terms

• asexual reproduction
• Parthenogenesis
• Meiosis
• Spermatophore
• thelytoky
• Arrhenotoky
• zygote
• dioecy
• hermaphroditism
• reproductive isolation

Usage Notes

Contrasts with asexual reproduction (cloning, apomixis, parthenogenesis). In entomology, 'sexual' often specifically denotes outcrossing between distinct individuals; hermaphroditic self-fertilization, though involving gamete fusion, is sometimes treated separately. Some authors reserve 'amphimixis' for true syngamy between separate parents to distinguish it from automixis (meiotic parthenogenesis with terminal fusion). The term is process-noun usage; no plural form exists.