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"Hug hormone" therapy to help fish socialize?

By Leonard Ho - Posted Oct 11, 2012 08:00 AM
Oxytocin is a chemical found in mammals. It's affectionately (albeit misleadingly) known as the “hug hormone" for its alleged ability to increase trust, generosity, cooperation and empathy. Scientists tested the piscine equivalent of oxytocin on fish's behavior ... and discovered interesting results!
"Hug hormone" therapy to help fish socialize?

Neolamprologus pulche. Photo by Guérin Nicolas

Adam Reddon from McMaster University experimented on African daffodil cichlids (Neolamprologus pulche) by injecting them with isotocin, the fish version of oxytocin.  He then observed their interactions with other fish following treatment; Reddon discovered the tropical fish became more responsive to social queues.

The cichlids grew more aware of their tank-mate's sizes and actually became more aggressive towards perceived challengers (ie larger specimens or even their own reflections) compared to saline-treated control counterparts who were aggressive towards every fish regardless of size.  On the other hand, when Reddon injected isotocin into "lesser' middle-of-the-social-heirarchy specimens, these fish became even more submissive in the group.

Previous isotocin studies have shown that goldfish and zebrafish were more likely to approach one another after treatment.  These findings demonstrate isotocin increases social sensitivity in fish and sheds insight on oxytocin's effects on mammals including humans.

Fishkeepers all know some fish are incorrigible bullies who will pick a fight with any fish.  Might isoticin treatment help them to better socialize with tank-mates?  Granted, such treatments are impractical and unlikely, but it's still interesting food for thought!


Journal Reference: Reddon, O’Connor, Marsh-Rollo & Balshine.2012. Effects of isotocin on social responses in a cooperatively breeding fish.

[via Discover's Not Exactly Rocket Science blog]

Author: Leonard Ho
Location: Southern California

I'm a passionate aquarist of over 30 years, a coral reef lover, and the blog editor for Advanced Aquarist. While aquarium gadgets interest me, it's really livestock (especially fish), artistry of aquariums, and "method behind the madness" processes that captivate my attention.


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