Indirect flight muscles of Mhc^DA2B/Mhc^DA2B, Mhc¹⁰/Mhc¹⁰ organisms fail to assemble properly and worsen with age: In late-stage pupae, there are poorly formed myofibrils with abnormal filament packing, and M- and Z-lines are extremely distorted. In 2h-old adults, there are severe defects in packing and alignment of filaments, with remnants of M- and Z-lines diffused throughout the sarcomere. In 2-days old adults, thick and thin filaments are dispersed randomly throughout the myofibril.

Indirect flight muscles of Mhc^DA2B/+, Mhc¹⁰/+ organisms show abnormal myofibril morphology: In late-stage pupae there are small myofibrils that show some filament packing disruptions, and poorly-formed M- and Z-lines. In 2h-old adults, myofibrils show further disruption in thick and thin filament packing and M- and Z-lines are aberrant or absent. In 2d-old adults some myofibrils appear fused, with poorly ordered thick and thin filament arrays, and Z-lines are more closely spaced.