What is Parthenogenesis?

by Stella Pfau

Parthenogenesis - say that five times real fast!

Parthenogenesis comes from the Greek root words, parthenos, meaning “virgin,” and genesis, meaning “origin.” The majority of animals need an egg cell and a sperm cell to reproduce, but more than 2,000 species are thought to reproduce parthenogenically, or without the need for sperm cells. This process allows creatures from honeybees and aphids to rattlesnakes and skinks to have so-called “virgin births.” For millions of years, animals have reproduced via parthenogenesis, first emerging in simpler organisms, and later in vertebrates.

There are two types of parthenogenesis. In one version, called automixis, an animal can merge a polar body with an egg, slightly shuffling the mother’s genes, to create offspring that is similar but not an exact clone of the mom. This occurs in vertebrates such as lizards and sharks, but often as a last-ditch effort for species facing adverse conditions. In the other version of parthenogenesis, apomixis, reproductive cells replicate via mitosis, and offspring are genetically identical to the parent. This version often occurs in plants but also in invertebrates such as wasps, ants, and aphids that can switch between sexual and asexual reproduction.

Want to see parthenogenesis in action? If you have a native plant or vegetable garden you may be able to find one of the most prolific asexual reproducers out there - aphids. In our habitat garden, they are particularly enjoying the stems and leaves of the goldenrod. Because aphids are able to reach maturity and reproduce within a week via parthenogenesis, they can create a lot of damage as there can be several hundred on one plant! They are particularly drawn to young plants and budding flowers and consume a large amount of the plant sap, which is mostly sugar and water, to meet their protein requirements. However, their bodies don’t need all of the sugar, so they get rid of it through their behinds in a substance called “honeydew.” This honeydew attracts other insects, such as ants, which have formed a symbiotic relationship with the aphids, harvesting and consuming the sticky honeydew and protecting the aphids from other predators. If ants aren't there, you may find natural enemies of aphids, such as ladybugs and lacewings that find them delicious.

However, these predators aren’t very effective as they usually arrive when the aphid population is relatively large. Most folks don’t love finding aphids on their plants but like any other creature, they sure are interesting, (anyone else an asexual sugar butt?) and a valuable part of our food chain.

Source: Wetzel, Corryn. “How some animals have ‘virgin births’: Parthenogenesis explained.” National Geographic, 25 Aug. 2020.