At the journal club today (10 April), we were impressed by the thorough study about sex chromosomes in snakes by Vicoso et al. (2013, PLoS Biology). Species representing three snake lineages in different stages of sex chromosome evolution were analysed with genomics and transcriptomics approaches. Main results? Snakes have either hetero- and homomorphic sex chromosomes, females are the heterogametic sex (ZW), heteromorphic species do not dosage compensate and there is rapid rate of evolution on Z - possibly due to a combination of drift and male-driven evolution. So these crawling ZW creatures seem to share many sex chromosome features with the avian ZW system, but not with mammalian XY. A highly recommended read!