Richard Kemeny is a writer.
The blind cavefish has unique accents in different caves.
A. Hartl/Alamy.
In the underground caves of north-eastern Mexico, groups of blind fish appear to be developing cave-specific accents. The linguistic split could contribute to ongoing speciation among the fish.
The Mexican tetra is no stranger to change. It exists in two forms, one with good vision that lives in light-drenched rivers, and the other blind with a translucent body, which began evolving 20,000 years ago as some fish populated dark underground caves.
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 is produced by their blind counterparts.
The Harvard University student wondered if the communication between fish in different caves differed.
They analysed 44 hours of fish chatter recorded in six caves across the three mountain ranges where it is thought to have taken place independently. The team focused on clicks and repeated clicks. The acoustic values they compared were the length of each click, pitch and rate at which multiple clicks were produced in sequence.
There were several differences between the caves. Clicks were pitched high in a cave called Molino, while they were deep and booming in a cave called Subterr. The fish in the cave called Pach fired off clicks up to 10 times more rapidly than in other caves, while in the cave called Tinaja, clicks were more drawn out. In a cave where hybrid populations of surface and cavefish are thought to live, the sounds were more varied than elsewhere.
The sounds in the cave were similar to nearby Chica, but also Subterr and Molino, which are in different regions. This supports the idea that the sounds were not related to physical proximity.
The team used a statistical analysis to assign sounds into groups and suggest different patterns in each cave.
Suzanne McGaugh at the University of Minnesota was not involved in the study. She says it would be interesting to see if communication varies between surface populations.
The new accents are probably the result of random genetic drift, according to a co-author of the study.
Communication difficulties could contribute to speciation according to the authors. It is possible that after a million years, they will not be able to understand each other.
She says that Astyanax is a good model to investigate the genetic basis of the evolution of sounds.
There is a reference to bioRxiv.
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