Crustacean cardioactive peptide (CCAP) is a highly conserved, amidated cyclic nonapeptide with the primary structure PFCNAFTGC-NH2 (ProPheCysAsnAlaPheThrGlyCys-NH2) and a disulfide bridge between Cys3 and Cys9.

It is found in crustaceans and insects where it behaves as a cardioaccelerator, neuropeptide transmitter for other areas of the nervous system and a hormone.

As well as C. maenas, CCAP has cardioacceleratory properties in Manduca sexta and Drosophila melanogaster;[1] it is a highly conserved protein found in species as diverse as moths and fruit flies in addition to the crustacean it was originally identified in.

In the crab Cancer borealis CCAP controls passage of food through the foregut by modulating the stomatogastric ganglion's pyloric rhythm.

There have been no mutant individuals of any species found to possess CCAP who have a genetic defect meaning they are not able to produce the peptide.