"As far as anyone can tell, the bdelloid rotifers are ancient asexuals: they appear to have been living entirely without sex for more than 85 million years. And each time we learn more details of their lifestyle, the wackier it becomes.

Evolving to live without sex is easy; all sorts of organisms do it the whole time. For example: aphids, weevils, snails, water fleas, nematode worms, scorpions, even the occasional lizard, have all been known to evolve asexuality. Instead of reproducing via eggs and sperm, asexuals can reproduce in any number of ways. For instance, some bud off a piece of themselves; the piece grows into a whole new animal. The bdelloids, like many other asexuals, reproduce by means of eggs that don't need to be fertilized.
No, evolving asexuality isn't the hard part. The hard part is making an evolutionary success of it."

From this charming article by Olivia Judson, charming as well.,