The skinned and eviscerated bodies of the oldest surviving KA mutants (P16–P17) and their age-matched littermates were placed into 1% potassium hydroxide (KOH) for 5 d. The bodies were transferred into a fresh solution of 1% KOH containing a few drops of 0.5% alizarin red S (Sigma, St. Louis, Missouri, United States) and left for another 5 d. The stained bodies were stored in glycerin and viewed under a dissection microscope.