Proliferating cells in suborbital tissue drive eye migration in flatfish

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Ichthyology

Background:

• Adult flatfish exhibit remarkable left/right body asymmetry, contrasting with larval symmetry.
• The most notable feature is eye migration, where one eye moves to the other side.
• The precise mechanism of eye migration has been debated for over a century.

Purpose of the Study:

• To investigate the underlying mechanism of eye migration in flatfish.
• To challenge the prevailing hypothesis that cranial asymmetry drives eye migration.
• To propose a new model explaining eye migration and asymmetry in Pleuronectiformes.

Main Methods:

• Microinjection of colchicine to inhibit cell proliferation in the suborbital tissue of the blind side in juvenile flatfish.
• Observation and analysis of eye migration and cranial asymmetry following inhibition.
• Comparative study across three species: Solea senegalensis, Cynoglossus semilaevis, and Paralichthys olivaceus.

Main Results:

• Inhibition of cell proliferation in the suborbital area prevented eye migration.
• Cranial asymmetry was found to be dependent on, not the cause of, eye migration.
• The findings challenge the established understanding of eye migration drivers.

Conclusions:

• Cell proliferation in suborbital tissue is the primary cause of initial eye migration.
• Cranial asymmetry is a consequence, not a cause, of eye migration.
• A novel model is proposed, explaining species-specific differences in eye migration and aiding understanding of Pleuronectiformes development and evolution.