What does digenesis mean?
Digenesis is a biological term describing a life cycle in which an organism alternates between two distinct modes of reproduction across successive generations — most typically between sexual and asexual reproduction. The phenomenon is well documented in certain cnidarians such as Obelia, where a sessile polyp stage produces medusae by budding, and those medusae in turn produce the next polyp generation through sexual reproduction. It is also characteristic of many parasitic flatworms, including flukes, whose generations alternate between sexual stages in a definitive host and proliferative larval stages in intermediate hosts. Digenesis is closely related to, and sometimes used interchangeably with, the broader concept of alternation of generations, though the latter term is more common in botanical contexts. The word derives from Greek roots meaning 'two' and 'origin' or 'birth', literally 'double generation'. Largely confined to zoological and parasitological writing, it remains a precise and useful label for this strikingly cyclical pattern of reproduction.
nounThe alternation of two distinct forms of reproduction or generation in an organism's life cycle, especially the alternation between sexual and asexual (or parthenogenetic) generations, as seen in certain cnidarians, trematodes, and other animals.
- The alternation of sexual and asexual (or parthenogenetic) generations in the life cycle of an organism, chiefly in zoology.
"In many trematodes, digenesis ensures that each generation differs markedly from the one before it."
"Obelia displays classic digenesis, alternating between a polyp generation that buds asexually and a medusa generation that reproduces sexually."
"The fluke's digenesis allows it to multiply rapidly within successive hosts."
Pluralized with -es following standard Greek-derived noun patterns; rarely needed since the word usually appears in the singular when describing a life-cycle type.
"Comparative studies have documented digeneses in several unrelated animal groups."
Some flatworm parasites live double lives so extreme that biologists gave the pattern its own name: digenesis, where one generation reproduces sexually and the next doesn't at all.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of digenesis
Digenesis comes from the Greek prefix di- meaning 'two' or 'double', combined with genesis, meaning 'origin' or 'generation'. The word entered scientific English in the nineteenth century as naturalists sought precise terminology for organisms that pass through two different reproductive modes. It shares its root with a wide family of English words derived from Greek genesis, including genetics, generate, and congenital.
How digenesis is actually used
A technical term used almost exclusively in zoology and parasitology; rare outside scientific literature. In botany, the comparable phenomenon of alternating haploid and diploid phases is usually called 'alternation of generations' rather than digenesis.
Easily confused with digenesis
Diagenesis refers to the physical and chemical changes that sediments undergo after deposition to become rock, whereas digenesis is a biological term for alternating reproductive generations.