Over a decade ago, Christine Grossen and colleagues raised an interesting hypothesis that the two versions of chromosome 1 in Triturus newts, 1A and 1B – responsible for the balanced lethal system – used to be distinct versions of a former Y chromosome. The exact scenario is too complicated to reproduce here, but suffice to say it persuaded us to test if 1A and 1B correspond to what is the Y chromosome in Lissotriton newts (the sister lineage of Triturus). In a paper out in Genome Biology and Evolution, my PhD student James France determined which chromosomes in Lissotriton newts correspond to the Y chromosome and which correspond to Triturus’ 1A and 1B. These are clearly not the same: a finding that does not bode well for Christine’s elegant hypothesis. Interestingly, the actual Y chromosomes of Lissotriton and Triturus are also not the same. This means that, on an evolutionary timescale, newts must have switched between Y chromosomes. How often has this happened? That is an exiting question to be addressed in future research.

Oh yeah, we can now also genetically determine the sex of Triturus newts, using the same approach as James previously perfected in Lissotriton newts.

Reference: France, J., Babik, W., Cvijanović, M., Dudek, K., Ivanović, A., Vučić, T., Wielstra, B. (2025). Identification of Y-chromosome turnover in newts fails to support a sex chromosome origin for the Triturus balanced lethal system. Genome Biology and Evolution 17(9): evaf155.