How to Make a Hermaphrodite

A 3D image of the nematode C. elegans, taken using a new imaging technique developed at MIT. The scale bar (lower left) is 50 micrometers. Credit: Michael Feld Laboratory, MIT.

A worm called Caenorhabditis elegans has a mating system in which individuals are either males or hermaphrodites (that make both eggs and sperm). However, the mating system in these nematodes arose from a progenitor that had only male and female individuals.

Now scientists have a better understanding of how things changed.

Female nematodes can be turned into hermaphrodites with the modification of just two genes, researchers reported in Friday's issue of the journal Science.

Chris Baldi and colleagues turned females of the C. remanei species into hermaphrodites through the modification of two genes, one involved in making sperm and another involved in activating them, the journal explaiend in a summary.

The authors propose that the evolution of the C. elegans mating system occurred in two steps. First, a mutation in the sex-determination pathways caused individual with two X chromosomes to produce sperm, and then a second mutation allowed the immature sperm to self-activate.