Analyzing scales of Astyanax mexicanus.
a–d Photographs of scales of surface fish from Rio Gallinas (left) and from cavefish from the Pachón cave (right). Examples are given for 3-year-old (top) and 5-year-old (bottom) individuals. Annual growth marks are indicated by the red ladder. Scale bar: 0.5 mm. e Correlation between age reads from scales and from otoliths for n = 33 surface fish individuals. f Boxplots showing the scale size/body length (TL) ratios of different A. mexicanus populations. The color code is indicated. *p < 0.05 and ***p < 0.0001, Mann–Whitney tests