Developmental effects of methimazole treatment. All E.
coqui specimens are early posthatching stage. Scale bars
represent 2 mm. (A) Control froglet with regressing
tail. Adult skin characters include leg bands (black arrowhead),
tubercles (white arrowhead), and raised dorsolateral ridges (white
arrow). (B) Methimazole-treated sibling.
(C) T3-rescued froglet. (D)
Control froglet, ventral view. Skin has sutured (arrowhead). Black line
indicates “snout–upper jaw” length, and white line represents
the “lower jaw–suture line” length, measured for morphometric
analysis (Table 2). (E) Methimazole-treated embryo, with
a gap between head and trunk skin (arrowhead). (F)
T3-rescued embryo. (G) Suture marks of newly
metamorphosed Rana pipiens (arrowhead).
(H–J) Meckel's cartilage (arrow) in control
(H), methimazole-treated (I), and
T3-rescued animals (J). (K)
Control froglet, exhibiting convergence of the rectus abdominis
(*) on the midline (arrowhead) and posterior elongation of the
pectoral muscles (white arrow), events inhibited by methimazole
(L) and rescued by T3 (M).