Monday, March 5, 2012

Fish Smell Fear Via Chondroitin

Aquatic animals use chemicals to communicate with each other, as water is an excellent medium for this type of communication. Hypersensitive to their environment, fish use chemical communication to receive and relay information about food, mating, and predation.

Scientists and aquarists have long known that fish, when wounded, release a substance that warns nearby fish of potential danger (when one fish is injured, the rest in a school will flee in panic). Until recently, this substance was known simply as "schrekstoff," which is German for "scary stuff." Thanks to a recent study published in Current Biology, schrekstoff has now been identified as a family of chondroitin sulfate-based compounds.

Chondroitin is a sugar naturally found in fish skin (it's also the stuff in fish oil that's good for joints). Researchers believe that this chondroitin is enzymatically released into the environment when a fish is injured. They also hypothesize that fish have evolved specialized neurons that are hypersensitive to chondroitin.

Apparently some fish are even sensitive to chondroitin compounds of different fish species, while others are less sensitive. I wouldn't be surprised if chondroitin compounds are most similar between two closely related fish species, and closely related fish are most sensitive to each others "schrekstoff." It would also be an advantageous adaptation for predator fish to have evolved a sensitivity to certain prey fishes' chondroitin compounds. However, this is conjecture, and obviously further research is required to know for sure.

It's a big development in aquatic husbandry to have finally found out after 70 years what exactly schrekstoff is. Now more than ever we know how important it is for the health of a communal aquarium to remove injured fish as quickly as possible.

Source article: Mathuru et al.: “Chondroitin fragments are odorants that trigger fear behavior.” Current Biology - March 20, 2012 print issue, DOI:10.1016/j.cub.2012.01.061

Advanced Aquarist.


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