The different effects of three Drosophila melanogaster dFMRFamide-containing peptides on crop contractions suggest these structurally related peptides do not play redundant functions in gut.

A Drosophila melanogaster dFMRFamide gene product, TPAEDFMRFamide, decreased crop contractions. However, DPKQDFMRFamide and SDNFMRFamide, also encoded in dFMRFamide, did not affect crop motility, which suggests these peptides are not functionally redundant in the crop and their unique N-terminal structures are important for activity. TPAEDFMRFamide-specific antisera did not stain the crop, which suggests it acts as a hormone. TDVDHVFLRFamide (DMS), encoded in D. melanogaster myosuppressin, stops crop contractions. TPAEDFMRFamide and DMS each contains a RFamide C-terminus; however, their effects on crop contractions differ, which suggests that unique receptors or different ligand:receptor binding requirements exist for these structurally related peptides.