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What bone changes occur during eye migration in flatfishes?
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pleuronectiform
Body plan and sexual dimorphism in the common sole (Solea solea) and dusky flounder (Syacium papillosum).
During the metamorphosis of pleuronectiforms, significant osteological changes occur to facilitate the migration of one eye to the opposite side of the head.12
Key bone changes include:
- Supraorbital Bar Reabsorption: As the eye begins its migration, the dorsal edge of the supraorbital bar is reabsorbed to create a path for the eye to move through the head.1
- Ossification: Once the eye completes its migration, the supraorbital bars ossify to form the interorbital bone.1
- Frontal Bone Shift: The frontal bone on the blind (bottom) side shifts toward the ocular (upper) side, eventually forming part of the floor of the optic capsule for the upper eye.1
- Skull Torsion: The overall process involves a twisting (torsion) of the frontal bones, the ethmoid region, and the mouthparts, which is the defining feature of the asymmetrical flatfish skull.1
These structural shifts allow the fish to transition from a bilaterally symmetrical larva to an asymmetrical adult adapted for life on the sea floor.2