Leukocytes participate in axon fragment removal. Axonal fragments were quantified at three different time points with the Analyze Particle plugin of the ImageJ software (see Materials and Methods). At 135 minutes postaxotomy, larvae lacking Schwann cells (leo1 mutants and larvae treated with the Schwann cell inhibitor AG1478) had significantly fewer axon fragments (P <0.05) than controls or spi1 morphant larvae depleted of leukocytes. At 195 and 405 minutes spi1 morphants had more axon fragments than controls or larvae lacking Schwann cells (P <0.05). n = 10 for each treatment; all experiments were carried out in neuroD::GFP transgenic fish.