Am. Nat. doi:10.1086/650725 (2010)

Sexual reproduction weeds out harmful genetic mutations. How, then, have the asexual soil fungi Glomeromycota managed to survive for 400 million years?

The answer may lie in the way that Glomeromycota reproduce, by releasing spores packed with hundreds of nuclei. By contrast, typical eukaryotic cells, including the spores of many other asexual fungi, contain only one nucleus. Teresa Pawlowska of Cornell University in Ithaca, New York, and Jean-Luc Jany, now at the European University of Brittany, Rennes, France, used three-dimensional imaging to watch Glomus etunicatum reproduce on carrot roots.

They found that a stream of nuclei pour into the spores from the fungus's thread-like vegetative branches. They also observed that some nuclei are eliminated and thus never passed on to spores, suggesting a method the fungus uses to screen out mutated nuclei.