Grammistins are peptide toxins synthesised by glands in the skin of soapfishes[1] of the tribes Grammistini and Diploprionini which are both classified within the grouper subfamily Epinephelinae, a part of the family Serranidae.
The grammistins have secondary structures and biological effects comparable to other classes of peptide toxins, melittin from the bee stings and pardaxins which are secreted in the skin of two sole species.
[3] A similar toxin has been found to be secreted in the skin of some clingfishes.
If ingested at a high enough dosage the toxin is lethal to mammals with some symptoms being similar to those produce by ciguatoxins.
The main purpose of the secretion of grammastin is defensive and when a lionfish (Pterois miles) tries to predate on a soapfish it immediately ejects it from its mouth, suggesting that it had detected the bitter taste.