The Paddlefish: Lover, Fighter, Aquatic Voltmeter

"I don't know whether this was a burning question for most people," said University of Missouri-St. Louis biology professor Lon Wilkens of the unexplained function of the paddlefish snout.

The spoon-shaped appendage, which gives the rare fish its name, has baffled scientists for decades. Do they use it for fighting? Mating?
Digging? Foraging? Wilkens, an expert in fish sensory apparati, seems to have figured it out, and his research is a step-by-step primer of scientific cleverness.

Focusing on juvenile paddlefish, which are more predatory and less filter-oriented than adults, he first compared their feeding behavior in lighter and darker conditions. There was no statistical difference in the number of plankton consumed.

Then he tried to disguise the chemical signals of plankton by saturating the fish tank with the equivalent of musk - a "plankton extract." Again, the paddlefish seemed unfazed.

So, he plugged up the fishes' nares - the fish equivalent of nostrils - and the paddlefish still found their food.

Trying one last idea, Wilkens dropped plankton encapsulated in gel, along with gel drops without plankton inside, and the fish overwhelmingly selected the plankton particles, by a ratio of 20 to 1.

What happened next? Read on....

The nose knows [Milwaulkee Journal-Sentinel]

Image: Tennessee Aquarium*