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Fig. 10. Remodeling of the larval flounder pectoral fin during spontaneous
metamorphosis and with altered thyroid status. Changes in fin morphology that
normally occur from 20 to 30 d.p.f. (A-G) can be induced with exogenous
thyroid hormone treatment from 7-11 d.p.f. (H-J), or inhibited by chemical
ablation of thyroid hormone with methimazol (0.1 mol l-1) for 6
weeks after pre-metamorphosis (K). Thyroid hormone induction (100 nmol
l-1 T3) for 1 week following 6 weeks of methimazol treatment
transforms the enlarged larval pectoral fin into the juvenile form (L). A
juvenile bilaterally symmetric variant (60 d.p.f.) has a normally remodeled
pectoral fin (M). (A-M) Bone (Alizarin Red) and cartilage (Alcian Blue)
processed tissues. Late pre-metamorphosis (A), late pro-metamorphosis (B),
early metamorphic climax (C), mid-climax (D), late climax (E), juvenile (F),
sub-adult (G). Untreated early pre-metamorphosis (H), 3 day T3-treated (I), 4
day T3-treated (J). fs, foramen scapulae; mdz, zone of matrix decomposition;
pop, postcoracoid process; pr, proximal radial; prp, precoracoid process; sco,
scapulocoracoid; mr, marginal rays. Bars, 0.2 mm (in A, for A-J), 0.2 mm (in
K, for K-M).
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