An unfertilized egg is an egg cell that has not fused with a sperm cell. For an egg to develop into a new organism and hatch, it typically requires genetic contributions from both a male and a female. However, there are exceptions where an unfertilized egg can develop and hatch.
The Necessity of Fertilization
For most species, an egg develops into an embryo through fertilization. This process involves the fusion of a male gamete (sperm) with a female gamete (egg). The sperm contributes its genetic material, which combines with the egg’s genetic material.
This union forms a single cell, a zygote, containing a complete set of chromosomes from both parents. The zygote’s formation initiates cell division and differentiation, leading to an embryo. Without this genetic combination and activation, development cannot proceed.
When Unfertilized Eggs Develop: Parthenogenesis
Despite the general requirement for fertilization, some organisms can develop an unfertilized egg into an embryo. This phenomenon is called parthenogenesis, from Greek words meaning “virgin creation.” It allows offspring to be produced without genetic contribution from a male, often by the egg restoring its diploid (two sets of chromosomes) state through mechanisms like automixis or apomixis.
Parthenogenesis is a natural reproductive strategy seen in many animal species. Invertebrates commonly exhibit this, including insects like aphids, water fleas, bees (where unfertilized eggs develop into male drones), wasps, and some stick insects. Among vertebrates, certain fish species (e.g., bonnethead and zebra sharks) and some amphibians can reproduce this way.
Reptiles also offer examples, with certain lizards like the New Mexico whiptail and some Caucasian rock lizards relying solely on parthenogenesis. Snakes, including the Brahminy blindsnake, and larger reptiles such as Komodo dragons, have demonstrated this ability, sometimes facultatively when males are absent. Parthenogenesis has also been documented in some birds, such as turkeys and quails.
Why Common Eggs Don’t Hatch
Eggs purchased from grocery stores do not hatch because they are unfertilized. Hens produce eggs as part of their natural reproductive cycle, even without a male bird or mating.
These eggs contain only the hen’s genetic material and lack the sperm contribution needed to initiate embryonic development. They are an ovulated cell intended for potential fertilization, not a pre-existing embryo. Even if incubated, these unfertilized eggs would not develop into a chick because the biological trigger for growth is absent.