Playing Roulette with Seven Sexes


Roli Roberts in the PLOS Biologue:

Have you ever watched “Seven Brides for Seven Brothers”? There are these seven brothers and, well you get the idea… But that was complicated enough with the two sexes that we boring old humans have – what if you had seven? That’s the exotic situation that the ciliate Tetrahymena finds itself in.

We can only speculate as to how these creatures handle their private lives, but thanks to a paper just published in PLOS Biology we now know how they decide which of the seven sexes to be.

PLOS Biology recently published another example of ciliate madness – the bizarre 16,000 chromosomes of Oxytricha. Each generation that creature makes a “working copy” of its genome by a massive cut’n'paste job that results in almost one chromosome per gene. Tetrahymena does a similar thing, though not as spectacularly (a mere 225 chromosomes – as published in another PLOS Biology paper), and that’s where the sex decision is taken.

Marcella Cervantes, Eduardo Orias and colleagues now show how this happens, and it involves playing genomic roulette.