αA-crys expression is controlled by trans-acting factors in F1 hybrid embryos. (A- D) In situ hybridization showing αA-crys expression in the lens of (A) surface fish (SF), (B) surface fish X cavefish (CF) F1 hybrids, and (C) cavefish X surface fish F1 hybrids, but not in (D) cavefish embryos at 72 hr post fertilization (hpf). The eye and lens are outlined by dashes in cavefish (D). Scale bar in A is 150 μm; magnifications are the same in A-D. (E) Semiquantitative RT-PCR showing αA-crys transcript levels in 40 hpf surface fish (SF), surface fish x cavefish F1 hybrid embryos (HY), and cavefish (CF) embryos compared to an 18S rRNA standard. (F) Profile of sequenced RT-PCR products from surface fish x cavefish F1 hybrid embryos showing a mixture of A (green) and G (black) residues at the first exon site distinguishing the surface fish from cavefish αA-crys alleles.