In rotiferland, freshwater bodies around the world, sexual reproduction has come and gone for 10s of millions of years. The question is why. The rotifers pictured have been infected by a parasitic fungus, their mortal enemy.
Typically, sexual reproduction has solved this problem for most other multi-celled organisms; it’s how we’ve kept diseases and parasites at bay for all our existence as a species, but sexual reproduction has inherent dangers too! There’s the problem of choosing and selecting a mate––a time and resource intensive process.
Rotifers took a different tack. There are about 273 different kinds of freshwater rotifers that have all come into existence without benefit of sexual shuffling. When things get tough, they dry up and blow away, and this may explained why they don’t need sex.