MyHC (“my-H-C”) genes are downregulated in this organism’s Short toes mutants. Myofibrils (“MY-oh-FYE-brils”) fail to organize in this organism’s cardiac mutants, which are used to study heart defects because they survive almost to hatching. Injecting iodine can stimulate this organism to undergo a process (10[1])it normally cannot (10[2])because it does not (10[1])endogenously produce thyroid-stimulating hormone. (10[1])The ALM assay performed in this organism established that nerve signaling, wound epithelium (“woond ep-ih-THEE-lee-um”), and the presence of cells from different axes (“AX-ees”) were sufficient for the regeneration of limbs. (10[1])While wild-types of these (10[1])neotenic (“nee-oh-TEN-ick”) amphibians (10[2])are olive-brown, (10[2]-5[1])captive (10[1])ones are commonly leucistic and pale (10[1])pink. (10[2])For 10 points, name this model (10[1])organism native to Mexico’s (-5[1])Lake Xochimilco (10[1])(“shoh-chee-MEEL-koh”), a salamander (10[1])with distinctive gill stalks. ■END■ (10[3])