Ultrastructural analysis shows that indirect flight muscles of homozygous flies contain no myofibrillar lattice, but arrays of thick filaments, often in loose bundles, are visible. Large striped filamentous assemblies ("zebra bodies") are present and these have a regular structure in which Z-disc like Z-bodies seem to occur in regular spaced stacks. Fine filaments, similar to thin filaments, protrude from these structures, filling the space between them.

Ultrastructural analysis shows that indirect flight muscles of heterozygous flies can contain some myofibrils of almost normal structure, which contain sarcomeres with clear Z-discs and M-lines, although the I-bands appear wider than normal. The phenotype is variable, so that some regions of the muscle contain very abnormal abnormal myofibrillar structures, especially under the sarcolemma, where zebra bodies are seen as an array of barely linked Z-discs.

Homozygotes show poor walking ability. Females produce significantly fewer eggs than wild type, and progeny consequently complete a major part of their development in utero.

Demembranated indirect flight muscles of homozygotes demonstrate a pleiotropic effect upon the accumulation of actin-associated myofibrillar proteins, actin, troponin-H, troponin-I, troponin-T and tropomyosin are missing. The myofibrils of heterozygotes show striated fibres with a tendency to fray.