Generation of spen^poc231 mitotic clones in the wing imaginal disc, using the FLP/FRT technique, causes a wing vein phenotype in the adult. This includes loss of vein material, which is mostly in the distal part of the wing, ectopic formation of material around the veins, thickening of existing veins and slight mis-localization of both longitudinal and cross-veins. Wing hair polarity is also disrupted and bristles are misplaced at the wing margin. Generation of spen^poc231 mitotic clones in the anterior compartment of the wing disc, using the FLP/FRT technique, affects both the micro and macrochaetae on the notum of adults. Macrochaetae are lost in some parts of the notum, gained in others and mislocalized. Duplicated trichogens and thormogens are not observed, indicating that cell fate specification is not affected. In both spen^poc231 maternal and zygotic embryos, the neurons of the peripheral nervous system show an abnormal distribution and morphology, and can be either fewer or greater in number than in wild type.

Mutant embryos derived from females containing homozygous spen^poc231 germline clones crossed to spen³/+ males (lacking both maternal and zygotic spen function) show alterations in the number of many peripheral and central nervous system cell types, and the development of other organs is affected. The number of lateral chordotonal (lch) organs in each abdominal hemisegment varies from 0 to 6, and is typically 4 (wild-type number is 5). Clusters containing the normal number are often disorganised. The lch axons stall prematurely.

In homozygous mutant embryos, the anterior portions of the lateral bars of the H-piece are missing or severely distorted. They also develop ectopic sclerotic patches of apparent head cuticle in ventral and ventrolateral thoracic regions, probably corresponding to ectopic head tissue.