Figure 1

Subterráneo pools contain a wide array of intermediate, hybrid phenotypes of Astyanax mexicanus. Photographs of our sample of 24 individuals fished with a seine net in the second pool of the Subterráneo cave. Some fish are surface-like (1, 3 and 18; eyed and pigmented), some are totally troglomorphic (5, 7, 8, 9, 10, …; eyeless and depigmented), some display mixed traits (2 and 15 are eyed and depigmented, whereas 21 is eyeless and pigmented) and some show intermediate phenotypes (for example, 17 with low pigmentation and very small eyes). Note that the pigmentation state of fish in a cave is not a good measure of its ability to make pigment cells; therefore, the various degrees of troglomorphy are best described by the size of the eyes, which is highly variable among these 24 individuals (for example, 1, 6, 18 and 20 have big eyes; 2, 3, 15 and 22 have small eyes; 11, 14, 17 and 19 have tiny eyes; and many are eyeless).