Show normal ability to develop ethanol tolerance.
The number and location of pigment-dispersing hormone-immunoreactive cell bodies in the brain and abdominal ganglia of homozygous flies is identical to wild-type. The arborisation field of these neurons in the medulla is smaller than in wild-type flies. Immunoreactive fibres occasionally leave the posterior optic tract in the median protocerebrum and project dorsally towards the calyces of the mushroom bodies.
Reduction in fibre number in the anterior optic tracts.
Homozygous viable. Homozygous germline clones display no maternal effect. Cell number in the medulla cortex is reduced by half: visual orientation behaviour is defective.
sol1/Df(1)HM44, and sol1/Df(1)17-257 flies have defective phototactic and optomotor responses similar to that of sol1 homozygotes. sol1/Df(1)GA104 and sol1/Df(1)GE263 flies have a more complex phenotype; these flies are not phototactic, but tend to disperse themselves evenly along a horizontal tube, they are hyperactive, and they have a weak, abnormal optomotor response. sol1/Df(1)GA104 flies have small optic lobes. uncl5 sol1 and stnA6, sol1 double heterozygotes have a normal optomotor response and normal viability.
Mushroom bodies have normal size and shape. Normal olfactory learning. Structural defects are restricted to visual system.
Extensive cell degeneration is seen in the outermost parts of the medulla cortex in the pupa. Cell degeneration is also seen in the cortex of the lobula complex and optic stalk.
The number of axons in the anterior optic tract (AOT) is reduced by 58% compared to wild-type. sol1 sounspecified double mutants have a loss of up to 83% of axons in the AOT compared to wild-type.
The volumes of the medulla and lobula complex neuropils are reduced by about 50%. Degeneration of ganglion cells of the cortex of the lobula complex is slightly more frequent than wild-type. There is extensive cell degeneration in the medulla cortex of pupae 33 hours after pupation. Some neurons in the optic lobe have an abnormal extension of their dendritic or telodendritic arborizations. Some neurons that normally link the lobula complex to the central brain, such as the giant V cell of the lobula plate, send branches into the medulla neuropil. The optomotor yaw response is normal, except at low temporal frequency, at which movement detection is somewhat impaired.
Criterion used in selection of mutant: histology
mnb1, rol1, sol1 has abnormal neurophysiology phenotype
rol1, sol1 has abnormal neuroanatomy phenotype
rol1, sol1 has abnormal optomotor response phenotype
rol1, sol1 has lobula plate phenotype
Fate mapping shows that the focus of the sol1 phenotype maps ventral to the ocellar and posterior orbital bristles.
Ultrastructural analysis indicates that the sol1 and sounspecified mutations act independently on nearly exclusive subsets of axons in the AOT.
Studies of gynandromorph flies show that the sol mutation acts primarily on cells of the medulla cortex. Degeneration of medulla ganglion cells occurs at an early stage of cellular differentiation, when their axons have not yet participated in the formation of the second optic chiasma.