Homozygotes and hemizygotes (over Df(3R)Cha7) exhibit a partial loss of motility at the mature L3 larval stage and an extended L3 larval phase followed by larval lethality with a paralytic phenotype. Homozygous germ-line clones also show the same phenotypes. endoA¹⁰/endoA²⁶ transheterozygotes show a strong loss of motility phenotype and lethality with paralysis during the L3 larval stage. No significant mEJP phenotype is seen in endoA¹⁰/endoA²⁶ larvae, suggesting synaptic vesicle exocytosis is normal. However synaptic vesicle endocytosis is affected, about 40% of boutons exhibit a reduction in dye uptake of >30% (compared to about 3% of boutons in controls), and <5% of boutons exhibit high uptake (compared to about 15% in controls). endoA¹⁰/endoA²⁶ larvae also show defects in the ultrastructure of neuromuscular junctions. IN about 30% of synapses the presynaptic terminal is almost completely depleted of synaptic vesicles (referred to as Grade III depletion). The few residual SVs are associated preferentially with the T-bar. i.e. the active zone. The plasmalamella of these synapses do not show an obvious accumulation of budding intermediates with a significant degree of membrane curvature. However, in the majority of cases (around 60%) there is substantial (but not an almost total) depletion of SVs (Grade II depletion), with the remaining being concentrated at the active zone. In ~10% of the synapses, there is no striking loss of SVs (Grade I depletion), but nonetheless an obvious change in ultrastructure, i.e. a remarkable increase in endocytic pits at the plasma membrane. Virtually all of these represent early-stage budding intermediates. In Grade I-III depleted synapses, there is an increased incidence of vacuoles, which are often found in close proximity to the plasma membrane and in the vicinity of te active zone. On average endoA¹⁰/endoA²⁶ larvae show a an ~80% reduction in SVs and a three fold increase in the occurrence of early stage budding intermediates. About 55% of synapses are grade I and about 40% grade II depleted. In endoA¹⁰ homozygous larvae the number of SVs is reduced by more than half and the occurrence of early stage budding intermediates increases 6-fold.