Scientists were amazed when an 18-year-old American crocodile at a zoo in Costa Rica produced an egg that had a foetus inside it without mating with a male. The foetus was almost a perfect clone of its mother, as it had no father. This is the first time this phenomenon has been observed in crocodiles.
The crocodile was captured in 2002 and has been living alone since then. She laid 14 eggs in January 2018, but only one of them seemed to be alive and was kept warm by the zoo staff. After three months, the egg did not open but showed a fully formed but dead foetus inside.
The zoo officials asked for help from a group of researchers led by Dr. Warren Booth, an evolutionary biologist at Virginia Tech, who is an expert in studying virgin birth. Virgin birth is a type of asexual reproduction in which an egg grows into an offspring without being fertilized by sperm. It has been seen in many species of birds, fish, reptiles and insects, but never before in crocodiles.
Dr. Booth and his team tested the DNA of the foetus and confirmed that it had no father. The foetus was more than 99.9% genetically identical to its mother, with only minor differences due to mutations. The researchers also found that the foetus was male, which is expected in virgin birth because crocodiles have temperature-dependent sex determination.
The researchers shared their findings in the journal Biology Letters on June 7, 2023. They suggested that virgin birth might be more common in crocodiles than previously thought, but it has been missed because most crocodiles live in groups and mate regularly. They also speculated that virgin birth might be an ancient trait that goes back to the dinosaurs, who were the ancestors of crocodiles.
Virgin birth is usually considered to be a backup plan for reproduction when mates are rare or missing. It can help a species survive in tough conditions or spread to new places. However, it also has disadvantages, such as reduced genetic diversity and increased risk of genetic defects. Virgin birth can also affect the sex ratio and population dynamics of a species.
The researchers hope that their discovery will inspire more studies on virgin birth in crocodiles and other reptiles. They also hope that it will raise awareness and conservation efforts for these endangered animals, who face threats from habitat loss, hunting and climate change.