Parthenogenesis in amphibians

Parthenogenesis is a special way some animals can reproduce without needing a partner. In this process, eggs develop and grow into new individuals all by themselves, without being fertilized by a sperm cell. This means the new baby comes from just one parent.

In the world of amphibians, which includes frogs, salamanders, and caecilians, parthenogenesis has been observed in many frog and salamander species. Scientists have found that these animals can create clones of themselves through this method. However, this interesting process has not been seen in caecilians so far.

Parthenogenesis is closely related to another reproductive method called hybridogenesis. In hybridogenesis, fertilization does happen, but the DNA from the father is not passed on to the next generation. This shows how flexible and diverse nature can be in helping animals reproduce and survive.

Artificial parthenogenesis

Scientists have found ways to make frogs develop without needing to be fertilized by a male. In 1911, a researcher named Oscar Hertwig used special sperm that had been weakened by radiation to help frog eggs start developing. This created almost normal baby frogs. Later experiments showed that mixing eggs from one type of frog with weakened sperm from another could also work.

Other methods, like using a needle to gently prick the eggs, have also helped frogs develop on their own. These experiments have led to fully grown frogs, including some that look different from normal frogs.

Parthenogenesis in nature

Salamanders are the oldest known animals that can reproduce through parthenogenesis, a way of making babies without a father. Scientists think this started between 3.9 million and 5 million years ago.

Many frogs and salamanders that reproduce this way come from mixing between two very similar species. For example, the edible frog is a mix of two other frog species. Some salamanders also come from mixing between different salamander species. Even though their moms come from one species, these salamanders don't have DNA from a specific old salamander species called Ambystoma barbouri.

Some of these special salamanders have extra chromosomes, which are like tiny packages of DNA. Having extra sets of chromosomes is common in these animals and can happen when different species mix. For instance, some salamanders have three sets of chromosomes, while others have four. This mixing affects how their bodies develop and can make it harder for their eggs to hatch. Hatching success for these salamanders can be low, possibly because of problems when their chromosomes try to pair up during egg development.

Modes of parthenogenesis and parthenogenetic-like reproduction in amphibians

Parthenogenesis is a special way some animals can have babies without needing a partner. In amphibians like some frogs and salamanders, this means eggs can grow and develop all by themselves. One way this happens is called gynogenesis, where an egg starts to divide after touching a sperm cell, but the sperm’s genes aren’t used. This has been seen in some salamander species.

Another way is hybridogenesis, where females mate with males from related species. The females use the male’s genes to help make eggs, but the male’s genes aren’t passed to the next generation. This is common in some European water frogs. There is also a process called kleptogenesis, where genetic material from both parents mixes, helping to keep genetic diversity in some salamander species.