Centrosomes are often detached from the spindle poles in mutant neuroblasts. 8% of mutant neuroblasts have disorganised astral microtubules during prophase. Mutant neuroblasts show spindle misorientation, with 20% lacking astral microtubules during metaphase.

mud¹ males exhibit enlarged and misshapen mushroom body structures formed by excessive Kenyon cell proliferation.

mud¹ females are semi-lethal.

mud¹ heterozygous flies demonstrate comparable patterns of landmark orientation, indicating similar responses to visual stimulation in Buridan's paradigm as control flies.

mud¹ heterozygous males exhibit reduced activity levels and walk slower than control flies.

Hemizygous males are fully fertile and produce normal numbers of motile sperm.

The Kenyon cell fibres in mud¹ mutants do not form a peduncle or lobe system, but instead form a greatly enlarged and misshaped calyx region.

Mutant flies produce a robust short-latency escape response, but over half the mutant flies do not give a consistent long-latency response. mud¹/mud⁴ flies are sensitive to halothane. mud¹ heterozygotes have normal sensitivity to halothane.

Flies have a number of brain defects, the exact phenotype depending on the genetic background. In the original genetic background in which it was induced, mud¹ produces the following phenotype; the calyx is 10 times normal size and misshapen, the peduncle and lobes are absent, the antennal lobe is enlarged, and the central complex is often misshapen. When placed in a Canton S background, the defects are more severe than in the original genetic background.

Semi-lethal.

Late third instar larvae show wild type mushroom bodies but imagos exhibit mutant phenotype: the lobe and stalk system of the mushroom bodies is missing and calyces are enlarged due to failure of the Kenyon cell axons to find their normal way through the central brain neuropil as the neuropil is completely degraded.