Lethal stage is during pre-eclosion. General morphology of the mutant larvae is normal. Mutant larvae respond to tactile stimulation at their anterior end by contracting at both ends and rocking back and forth in place. After a few seconds of this behaviour, the larvae cease this abnormal movement and return to a normal forward-crawling motion. This contrasts with wild-type larvae which respond by showing a characteristic escape behaviour of 1-3 reverse peristaltic movements followed by a lateral turning behaviour. Homozygous and tutl4/Df(2L)ed-dp larvae have a severely compromised ability to roll over from an inverted position; the time required to right themselves is significantly (nearly 20-fold) longer than control larvae. The rate of executing peristaltic contractions during normal locomotion is slightly reduced (less than 15%) in homozygous larvae compared to wild type. Homozygous embryos show no abnormalities in the morphology of the longitudinal tracts or the anterior and posterior commissures. No transient defects in axonal patterning have been detected through stages 9 to 17. Brain morphology and size and shape of the axon scaffold appears normal. No abnormalities in the Fas2-positive longitudinal connectives or in the motor axon pathways that exit the CNS to innervate the musculature are seen. The ventral unpaired median axons and segmental and intersegmental nerves also appear normal. No defects in the PNS have been detected. The longitudinal connectives appear normal in third instar mutant larvae. Muscle innervation and presynaptic morphology at the neuromuscular junction (NMJ) appears normal. The kinetics and amplitude of the excitatory junctional currents (EJCs) at the NMJ are not significantly different from wild type.
