TSG101¹¹³⁹ mutant trachea exhibit selective terminal cell pruning. They ramify much less extensively than in wild-type, but the branching defect appears selective for side branches and possibly other later rounds of terminal branching. These mutants also exhibit a terminal cell gas-filling defect that typically affects only new or distal portions of sub-cellular tubes. The tip-clearance defects are variable, with some mutant termina cells more severely affected than others, even within the same mosaic animal.