Many people have horror stories about having their mouths washed out with soap when they were younger. Turns out humans aren’t the only ones who don’t like it.
Enter the Soapfish, a fairly blah looking fish that hangs out on tropical reefs. Underestimate it at your peril. This kick butt fish just took on one of the deadliest fish in the world and swam off to tell the tale.
This fish gets its name from the toxic slime it generates when stressed is thought to protect it from potential ‘soap killers’. Being an ever-curious bunch, we decided to test out how effective this was as a mode of defence against the world’s most venomous fish…(insert dramatic music) the STONEFISH.
We placed a Soapfish in with several Stonefish and waited to see what happened. As expected the Stonefish swallowed the Soapfish when it came within striking distance BUT then spat it out just as quickly (science can be a torturous thing at times…). To see all the gory detail we filmed it in high speed.
What was really interesting is that after one failed attempt at eating the Soapfish, the Stonefish didn’t try again, even after long period of time. So they learnt their lesson. At one point the Soapfish even sat on the head of the Stonefish and it wasn’t budging a bit.
To test if this was just because of the residual soapy toxin in the Stonefish mouths we put in a Damsel fish and you know what? They gobbled it right down without a second thought.
So it must be an extremely powerful toxin to get that sort of reaction and so quickly. Another thing that is really interesting is that the Soapfish is scaleless, so perhaps this secretion is also an adaptation to get the toxin out quicker?
Some studies also suggested that the toxic slime could decrease the friction in the water, requiring less energy to swim, which is advantageous when you spend most of your time in the middle of the water column. Kind of like, sharks and the denticles that cover their body.
While there are more questions than answers with this little known fish, the Soapfish can now claim the title of defeating the world’s most venomous fish, which will no doubt give it bragging rights down at the local reef on a Saturday night.
That’s the nature of science.
