Files in this Data Supplement:

• Movie 1 -

  Movie 1. Sinistral surface skimming. This 16 d.p.f. late pre-metamorphic larva skims the water surface for brine shrimp with its left eye (non-migrating eye) only. This larva metamorphosed with sinistral behavioral and morphological asymmetry.

• Movie 2 -

  Movie 2. Sinistral tracking behavior. The 16 d.p.f. larva in the foreground (and others in the background) swim beneath the water surface and track brine shrimp using their left eye only. These larvae will all metamorphose with sinistral behavioral and morphological asymmetry.

• Movie 3 -

  Movie 3. Dextral tracking behavior. This 16 d.p.f. larva is tracking brine shrimp near the surface using its right eye only. This larva metamorphosed with dextral behavioral and morphological asymmetry.

• Movie 4 -

  Movie 4. Upright feeding behavior. This 12 d.p.f. early pre-metamorphic larva always feeds swimming upright, and does not display any obvious lateralized behaviors yet.

• Movie 5 -

  Movie 5. Sinistral morphology/Dextral behavior. This very rare post-metamorphic (36 d.p.f.) phenotype has normal sinistral morphology, but always settles and swims with dextral behavior; thus, both eyes are always touching the bottom!

• Movie 6 -

  Movie 6. Metamorphic climax tilting. This larva in early climax is displaying its default swim position with its left side tilted towards the surface. The particles in the water are debris, not brine shrimp.

• Movie 7 -

  Movie 7. Developmental morphing sequence of the flatfish skull. This movie depicts asymmetric skull development before and during metamorphosis. The morphed images are derived from the six developmental stages of larvae featured in Fig. 4.

• Movie 8 -

  Movie 8. Thyroid hormone-induced settling behaviors. These larvae were treated with thyroid hormone (100·nmol·l^–1 T3) for 3 days starting at late pre-metamorphosis (15 d.p.f.). They now all have settled behavior, and rarely swim. Note that all the fish are settled on their right sides. The fish in the foreground is displaying particularly aggressive behavior. One very large and much older (60 d.p.f.) juvenile is briefly seen in the same tank.

• Movie 9 -

  Movie 9. Settled symmetrical variant. The first fish that appears is a typical settled juvenile with sinistral morphology and behavior; note the disconjugate eye movements. The second fish to appear is also a settled juvenile with sinistral behavior, but it has metamorphosed with bilaterally symmetric morphology. Its right eye has failed to migrate and always touches the bottom.