The Secret Life of Tiny Parasites: How They Change Over Time

In the vast world of animals, some have taken a different path. Instead of becoming more complex, they've become simpler. This is especially true for parasites. Scientists have been studying a group of tiny creatures called Syndermata. This group includes rotifers, Seisonidea, and thorny-headed worms. Some of these creatures are free-living, while others are parasitic. The researchers looked at the DNA, RNA, and physical traits of 25 different species. They found something fascinating. As these creatures became more parasitic, they lost many things. They lost tiny gene regulators called microRNAs. They also lost protein-coding genes and even physical traits. The most extreme case was the parasitic thorny-headed worms. They lost about 85% of their microRNAs. They also lost 50% of their core genes. They even lost many physical features, like their digestive system. This shows a clear link between losing microRNAs and becoming simpler. The study also found some interesting patterns. Losing one microRNA family often meant losing around 400 protein-coding genes. It also meant losing 10 core genes. Similarly, losing four microRNA families and 34 core genes was linked to losing one physical trait. This suggests that microRNAs play a big role in maintaining complexity. But why does this matter? Understanding how parasites simplify their biology can help us grasp the basics of animal evolution. It shows that becoming a parasite isn't just about losing traits. It's a complex process involving many genetic changes. This can help us understand how life evolves in different ways.