SIFamide illustrates the rapid evolution in Arthropod neuropeptide research.

This review is focussed on SIFamide. This neuropeptide was discovered as a result of an extensive purification process, typical for 20th century physiology, of an extract of 350,000 flesh flies. Our knowledge of SIFamide greatly expanded since the first publication in 1996. Describing the minor and major findings on this peptide is our lead to summarise a number of innovations that recently became common in research on Arthropods. Mass spectrometry, nanoLC, whole mount immunocytochemistry, genome sequencing, deorphanizing receptors and functional gene knock downs are aspects that dramatically improved and changed peptide research. Some of the techniques mentioned in this review were of course applied before 1996, but they were not widespread. Although the focus of the review is on insects we incorporated the data of SIFamide in Crustaceans as well. SIFamide illustrates that crustaceans and insects might have more in common than was previously anticipated. Today, six isoforms of SIFamide are discovered in many crustaceans, several insects and a tick. The sequence of SIFamide is extremely conserved among these species. Deorphanizing its receptor in Drosophila, learned that both the ligand and receptor are impressively conserved, pointing at a crucial function. Immunohistochemistry and mass spectrometry data reveal that SIFamide is present in the crustacean brain and gut, but restricted to four neurons in the insect pars intercerebralis. The immunoreactive patterns in the brain refer to a neuromodulatory role in combining visual, tactile and olfactory input. Eventually, targeted cell ablation and RNAi revealed that SIFamide modulates sexual behaviour in fruit flies.