In the underground caves of north-eastern Mexico, groups of blind fish appear to be developing cave-specific accents. The linguistic split could eventually contribute to ongoing speciation among the fish.
The Mexican tetra (Astyanax mexicanus) is no stranger to diversification. It exists in two forms: one with good vision that lives in light-drenched rivers, the other blind with a translucent body, which began evolving perhaps only 20,000 years ago as some fish populated dark underground caves.
Like many fish, A. mexicanus uses noise to communicate. It produces at least six distinct sounds for this, though their meaning seems to have shifted among the cave-dwellers as they adjusted to living in darkness. A particular form of sharp click used by sighted fish in aggressive encounters, for example, is produced by their blind counterparts while foraging.
Carole Hyacinthe at Harvard University wondered if the communication also varied between fish evolving in different caves.