Excision of the P{EP} element in P{EP}MAPk-Ak2GE3296 results in deletion of the region downstream of the insertion site, which includes the second exon and part of the third exon of MAPk-Ak2.
Approximately 32% of MAPk-Ak2Δ38 mutant larvae exhibit a melanotic phenotype in response to strong salt stress (0.2M NaCl). A "black dot" is seen in the posterior hindgut and the affected hindgut epithelium appears pathologically altered. 27% of mutants exhibit this phenotype when raised on food containing 0.1M NaCl. The phenotype is not seen when larvae are raised on normal food.