Researchers have found, in the world’s longest animal, one of the most potent insecticidal peptides ever discovered (Sci. Rep. 2018, DOI: 10.1038/s41598-018-22305-w). From the sea bottom off the western coast of Sweden, Ulf Göransson of Uppsala University and coworkers collected bootlace worms, Lineus longissimus, which are up to 50 meters long. When poked, the worms released mucus that contained three novel peptides. The researchers sequenced one of these, which they called nemertide α-1, and made more of it by chemical peptide synthesis to obtain a sufficient amount to study. Nemertide α-1’s solution NMR structure showed that it folds around an inhibitor cystine knot, a peptide motif containing three disulfide bridges. Tiny amounts injected into crabs and cockroaches paralyze and kill the organisms. Nemertide α-1 works by slowing the inactivation of sodium channels in nerve cells, forcing the channels into a constant “on” state that causes initial hyperactivity and then low muscle tone and subsequent paralysis. But it works 100 times better on insect sodium channels than it does on mouse and human sodium channels. The compound’s high insect-killing potency and selectivity points to the “potential use of α-nemertides in the development of novel insecticides,” the researchers say.