Which came first: the chicken or the egg? The question is common and not easy to answer. But one could say that laying eggs (ovaries) has deep roots in evolution and arose before the first animals ventured onto land. But since then there have been many independent transitions to live birth throughout the animal kingdom. Many insects, fish, reptiles and especially mammals now give birth to surviving offspring. The oldest evidence of a live birth to date is a 380-million-year-old fossil of an armored fish. However, it remains unclear what genetic changes are needed to drive this special evolutionary process. An international research team led by Sean Stankowski from the Institute of Science and Technology Austria (ISTA) has now used a marine snail as an example to analyze which regions of the genome contribute to whether individuals lay eggs or give birth to live young. Results Published in the specialized magazine “Al-Ilm”..
Scientists have studied this phenomenon using the example of a marine snail Litorina saxatilis This is because the evolution of saltwater animals into living organisms occurred over a period of only 100,000 years – a very short period in evolutionary terms. Mammals, on the other hand, have been giving birth to live young for about 140 million years. In addition, live birth is the only known trait that… L. saxatelis They differ from their relatives who lay eggs. This makes it easier to look for the genetic cause of the difference. The team focused on about 50 genetic changes spanning the entire snail genome.
“We believe that natural selection was the driving force of the transformation process. In the womb, young animals are better protected from dehydration, predators and physical damage.Sean Stankowski, evolutionary biologist
“We don't know exactly what individual regions are doing,” Stankowski said. According to a press release from ISTA. “However, by comparing gene expression patterns in egg-laying and parturient snails, we were able to link many of them to reproductive differences.” Vivipary evolved gradually through the accumulation of many mutations that arose over the past 100,000 years. This has allowed the snail to spread to new areas and habitats where conditions are not suitable for eggs. “We believe that natural selection was the driving force for this transformation,” Stankowski explained. In the womb, young animals are better protected from dehydration, predators and physical damage.
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