Context: Recently female crocodile in a Costa Rican zoo laid a clutch of eggs. That was peculiar: She’d been living alone for 16 years.
How does a virgin birth happen?
- As an egg cell matures in its mother’s body, it divides repeatedly to generate a final product with exactly half the genes needed for an individual.
- Three smaller cellular sacs containing chromosomes, known as polar bodies, are formed as byproducts. Polar bodies usually wither away.
- But in vertebrates that can perform parthenogenesis, one polar body sometimes fuses with the egg, creating a cell with the necessary complement of chromosomes to form an individual.
- This process of Vergine birth (offspring containing only genetic material from its mother) is known as parthenogenesis
Parthenogenesis can be seen in the following creatures
- King cobras
- California condors
- Some birds
Why parthenogenesis occurs?
- It’s possible that parthenogenesis gives a species the ability to survive extended periods when no mate is available.
- A fresh individual, bearing largely the same genes as its parent, might live long enough for a mate to arrive, thus allowing sexual reproduction, which tends to produce hardier offspring.
- But it is also possible that parthenogenesis is simply a trait that doesn’t have enough downsides for evolution to weed it out.
- It is not necessarily a response to stress or even a lack of mates. In 2020, scientists discovered that lizards can mate and then lay clutches of eggs where some are normal offspring and some are parthenogens.
- It’s an ability that can be switched on or off, and it is perhaps controlled by a single gene.