Scary Stuff: Fright Chemical Identified in Injured Fish »

In the 1930s Austrian animal behavior scientist Karl von Frisch accidentally injured a minnow in a tank. He noticed that the other fish in the tank began alternately darting back and forth and freezing in place—classic predator-evading behavior. Subsequent experiments established that the frightened fish were responding to chemicals released from the skin of their injured peer—a cocktail dubbed “schreckstoff,” which is German for “scary stuff.”

For decades, the chemistry of schreckstoff remained unknown. In the 1970s and ’80s some scientists discovered that exposing fish to a chemical known as hypoxanthine-3-N-oxide (H3NO) frightened them in the same way as schreckstoff, albeit to a lesser degree. H3NO, they concluded, was probably the active compound in schreckstoff. But there was a problem with that idea: scientists had never reliably detected H3NO in fish skin. Instead, some researchers proposed, H3NO may mimic the genuine active compound.

Now, Ajay Mathuru of Neuroscience Research Partnership in Singapore, Rainer Friedrich of the Friedrich Miescher Institute for Biomedical Research in Switzerland and their colleagues think they have isolated the key ingredient in schreckstoff—a sugarlike molecule named glycosaminoglycan (GAG) chondroitin. Their findings appear online in the February 23 issue of Current Biology.