Peptide-mediated behaviors in marine organisms Evidence for a common theme

Biology has many common themes such as DNA, RNA, the other biopolymers, and their building blocks. Chemical communication systems have similar common themes. An example is the common usage of amino acids, sugars, and nucleotides as food cues. It is likely that communication systems began with the evolution of specific meanings for preexisting molecules. One class of molecules used in specific communication is peptides. These peptides are generated as part of the body odor of organisms in aquatic environments and can act at a distance or by contact. Evidence is given for a common type of peptide receptor system. Four peptide-mediated behaviors, three in diverse crustacean groups and one in a mollusc, are discussed. The behaviors are of major survival importance, are cued by nanomolar concentrations of peptides generated by serine proteases, and the basic carboxy terminal amino acid is required. The behaviors include attraction to new shells, attraction to living prey, release of larvae, and induction of larval settlement behavior. Studies with pure di- and tripeptides show the same molecules evoke larval release behavior, shell attraction responses, and larval settlement behavior. The pure compounds are effective at nanomolar or lower concentrations. Similar peptides function as specific cues in vertebrates in response to wounding. Thus, peptide communication using serine protease-generated peptides appears to be a common theme.