Scientists have concluded that bdelloid rotifers have likely been asexual for 100 million years. what evidence supports this conclusion?

The evidence that supports the conclusion that bdelloid rotifiers have likely been asexual for 100 million years is the comparison of the DNA of bdelloids and that of sexually reproducing rotifer species.
Based on this comparison, the scientists could clearly see the difference between the reproduction cycle of rotifier, and that of bdelloid, or rather the lack of it.